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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: 454Man on August 06, 2013, 09:00:19 PM
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At my wits end on this. I believe there's a short between the supply write going to the fuse box and it's connection to or in the fuse box. Blade type fuses. If I have to many things on at once it shorts(losses it's connection to the battery. The volt meter on the dash goes all the way to the right. But I go to the battery under the hood and get just 12 volts. Does anyone have pics of the fuse box separate from the truck?
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Changed parts list: starter, alternator, battery 2 ignition switches, fuse links (now replaced with breaker style fuse,) wires in charging system currently about to change the wire going from the alternator to starter. I know this has to do with the amp draw on the fuse box after all the trial and error.any help and opinions appreciated.
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How new are your battery cables?
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I assume you replaced the parts listed in your second post, chasing this complaint. :o Stop throwing parts at it!
If I'm tracking with you, when you turn too many appliances ON the voltage available to those appliances drops off toward zero. Are all of the electrical appliances in the truck affected, or is it limited to a particular area of the truck (e.g., dash and cab interior only, exterior lights, just certain accessories, etc)?
Do you have a test light? Do you have a voltmeter? Do you know how to make voltage drop tests and what they indicate?
Have you verified that the engine, cab and frame are properly grounded to the battery?
So we don't confuse each other, it sounds more like you're describing excessive resistance buildup in a circuit (a partial open or poor connection) than a short.
As zieg recommended, check your battery cables and cable connections first. Then move on to the questions listed.
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Have you verified that the engine, cab and frame are properly grounded to the battery?
Start with that! Search "engine ground strap" on this forum.
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have you taken the firewall connector off yet? check the connection there also
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have you taken the firewall connector off yet? check the connection there also
I Haven't taken the fuse box connector off yet. I didn't want to break it (trucks my daily) I will admit I've never taken one off. Prob could be right there...
I assume you replaced the parts listed in your second post, chasing this complaint. :o Stop throwing parts at it!
If I'm tracking with you, when you turn too many appliances ON the voltage available to those appliances drops off toward zero. Are all of the electrical appliances in the truck affected, or is it limited to a particular area of the truck (e.g., dash and cab interior only, exterior lights, just certain accessories, etc)?
Do you have a test light? Do you have a voltmeter? Do you know how to make voltage drop tests and what they indicate?
Have you verified that the engine, cab and frame are properly grounded to the battery?
So we don't confuse each other, it sounds more like you're describing excessive resistance buildup in a circuit (a partial open or poor connection) than a short.
As zieg recommended, check your battery cables and cable connections first. Then move on to the questions listed.
Thanks! The factoty voltmeter pegs out to like 18 volts because the connection to the battery is lost and it only sends charging amps to inside.(when this happens my windows go up crazy fast) if I select the up button. It will also make my headlights and break lights stupid bright, so bright it blows the left and right signal filament inside the tail light bulbs :-()
Because I have the breaker style fuse installed out resets and either does it again or goes back to normal.
On the ground idea. Guess I could add some more. Can never have enough. I have the small one from the Neg Batt cable to radiator support. Neg Batt cable to alternator, ground strap to firewall and that's it what else do I need? Again thanks :-)
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You're full-fielding the alternator. Which alternator are you using? What happens if you disconnect the alternator?
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10si
Did not unplug the alternator. Won't that fry it?
Full- fielding?
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On the ground idea. Guess I could add some more. Can never have enough. I have the small one from the Neg Batt cable to radiator support. Neg Batt cable to alternator, ground strap to firewall and that's it what else do I need? Again thanks :-)
You're missing one. There should also be a ground strap from the front of the driver's side head of the engine to the frame rail.
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On the ground idea. Guess I could add some more. Can never have enough. I have the small one from the Neg Batt cable to radiator support. Neg Batt cable to alternator, ground strap to firewall and that's it what else do I need? Again thanks :-)
You're missing one. There should also be a ground strap from the front of the driver's side head of the engine to the frame rail.
thanks :-)
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10si
Did not unplug the alternator. Won't that fry it?
Full- fielding?
Unless you're running more than one battery, the only way to increase voltage above 12.6 volts is if the alternator goes into an uncontrolled overcharge. Full-fielding means the alternator rotor (the field) is receiving full or nearly full battery voltage, forcing the stator to output maximum electrical energy. In other words, the regulator isn't doing its job either because of an internal problem or because it is being tricked by an external wiring issue.
Unplugging the two-wire connector from the regulator will not damage the alternator. It should just turn it OFF. If the alternator continues uncontrolled output with the regulator unplugged, there's a short inside the alternator.
Did the problem begin before or after you replaced the alternator?
Post a clear pic of the wiring harness connections to the alternator.
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On the ground idea. Guess I could add some more. Can never have enough. I have the small one from the Neg Batt cable to radiator support. Neg Batt cable to alternator, ground strap to firewall and that's it what else do I need? Again thanks :-)
You're missing one. There should also be a ground strap from the front of the driver's side head of the engine to the frame rail.
thanks :-)
Same problem 2 new alternators. Connector at alternator is new.
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I'll post a pic after work just don't make Fun of my birds nest lol
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Same problem 2 new alternators. Connector at alternator is new.
I'll post a pic after work just don't makeFinn of my birds nest lol
LOL - Never cared much for birds nest soup.... ::)
When you take the pics, our main interest is in where/how the wires are connected/routed. In the meantime make sure all grounds are in place and connections are clean and tight. Do you recall the circumstances when the problem began?
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The problem just started happening out of the blue. it happens mainly if I let the truck sit for more than 3 days. Out like I said b4 if three is to much amp draw inside.The headlights don't cause the prob.
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When this happened one time I pulled all the fuses out the fuse box(to rule out those accessories) and it still continued to peg the volt meter.
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(http://img.tapatalk.com/d/13/08/08/ugeda7an.jpg)
(http://img.tapatalk.com/d/13/08/08/te3y3y3a.jpg)
(http://img.tapatalk.com/d/13/08/08/6equ2ede.jpg)
(http://img.tapatalk.com/d/13/08/08/jyve2e6e.jpg)
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I see a couple of wiring problems you'll need to correct later. First things first...
I need to know exactly where the "red" and "white" wires that plug into the regulator tie into the cab wiring. As you follow the wires, physically inspect the harness for damage and the condition of terminal ends, splices and connections. Post pics of where the wires connect.
Do you have a voltmeter and test light?
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I have a fieldpeice multimeter and use it daily for my job :-) I have a couple things bypassed as a way to rule out things. I've ohmed wires all wires under the hood and replaced the ones that showed any resistance or (OL) next I'm gonna add a 4 or 8 gauge wire from the alternator.then maybe the fuse box from another truck that looks good. Any thoughts?
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Just added that engine to frame ground. Will see if that helps tomorrow
Does the fuse box split in half? Like one side in the cab and the other under the hood on the fire wall? I'm looking at it and can't tell.
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theres one bolt i think 10 mm just took one off and i dont remeber what it is. its a common problem for these to be melted and might cause a problem or two.
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Ah yes... some reason I thought that was some kinda old sealant maybe mine is melted I'll take a pic tomorrow. So one bolt? Does three box come out I'm two parts or one? Thanks.
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the one bolt is on the engine side and it acts like a quick connect. the wire harness will stay under the hood and the fuse box part will stay in the firewall
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I have a fieldpeice multimeter and use it daily for my job :-) I have a couple things bypassed as a way to rule out things. I've ohmed wires all wires under the hood and replaced the ones that showed any resistance or (OL) next I'm gonna add a 4 or 8 gauge wire from the alternator.then maybe the fuse box from another truck that looks good. Any thoughts?
If the alternator is rated less than 70 amps output, build the charge lead from 8-ga wire; between 70 and 100 amps output, use 6-ga wire; between 100 and 150 amps output, use 4-ga wire; over 150 amps out, use 2-ga wire. Protect the charge lead with 6" of the appropriately sized fusible wire at the charge lead's battery connection. Crimp then solder all terminal ends.
The bulkhead connector is a three-piece assembly. The engine harness is secured to the connector using the screw Irish mentioned. Inside the cab the connector is secured to the firewall with two long screws that also piggyback the fuse box onto the connector. The two connector halves are sealed with a black tar-like antioxidant. The #1 regulator lead is a resistance wire.
Still need to know where you have the regulator wires connected into the cab harness.
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I added anothere ground from the engine to the frame and so far all is well. I'll give it a couple days though. I'll trace those wires bd I'm sure there going to the factory location as the truck was all factory b4 I swapped the engine, all down to the smog stuff
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Happy day! Glad to hear the engine ground resolved it!
Some additional information:
The two wires from the regulator serve the following purposes: The #1 lead is the "exciter circuit" connected to ignition power through a resistance (either a resistance wire w/ factory gauges, or the charge light w/o gauges). The resistance is important to prevent the alternator from trying to charge the battery through the small gauge ignition circuit under certain circumstances. The #2 lead is the "sensing or regulator circuit" connected to battery. It senses system voltage so the regulator can adjust alternator output to maintain a target charge voltage of 14.2 volts (13.8 - 14.5 volts is the acceptable range). Ground is the zero reference the regulator needs to accomplish its task. A fault (unwanted resistance) in any of the three circuits will defeat the regulator's purpose. Make sure that you crimp, solder and heat shrink all terminal ends and splices as you work your way through the electrical system for the best results over the long run.
Well done!
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Thanks for the info I'll post any results in a few days
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the one bolt is on the engine side and it acts like a quick connect. the wire harness will stay under the hood and the fuse box part will stay in the firewall
thanks
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On the ground idea. Guess I could add some more. Can never have enough. I have the small one from the Neg Batt cable to radiator support. Neg Batt cable to alternator, ground strap to firewall and that's it what else do I need? Again thanks :-)
You're missing one. There should also be a ground strap from the front of the driver's side head of the engine to the frame rail.
thanks!
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No problem. We always think of engine, frame, and cab as being ground, but in fact they are all shock mounted to each other, so there have to be ground straps -- cab to engine to frame -- to get them all to agree on "ground". Easiest thing in the world to leave one off when you work on or replace the engine, and then absolutely anything can happen.
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This morning I tested out the new ground I added last night. I cranked the AC, radio, and fiddled with the windows. Nothing bad yet :-) we will see.
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Well still have the problem guys. Did the same test and back to the old prob. Except this time after I turned the blower motor down off high.
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All went back to normal... I'm gonna try taking the fuse box apart from the fire wall and see what I can find
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Well cleaned the contacts on the fuse box connectors and still... I'm ok if I don't turn the fan on high, head lights and all... Just the fan. I really don't think it's the fan because I've had it unplugged b4 and had the same prob... Dang
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BD where is this resistor wire your talking about? I'm still at a lost. I think the next thing will b is to upgrade the charging wire from the alternator
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Keep a cool head. You'll find the problem if you're systematic.
Absolutely verify that the alternator is properly grounded by installing a temporary jumper between the alternator case and the battery negative post. This should determine beyond any doubt whether you still have a ground problem to correct.
If the temporary ground jumper doesn't correct the problem, take a very close look at the red, 12-gauge wires that feed power into the cab from the starter. Inspect the cable connections at the starter, firewall junction block and bulkhead connector for any signs of looseness and/or heat stress. Don't tear the fuse block any further apart just yet. Simply unplug the connector on the engine compartment side and look for heat damage, distortion of the connector, etc. You may need to clean away the black sealant to see the connector and terminals clearly. Concentrate on the heavy-gauge red and pink wires.
Based on what you've posted to date, I think you're going to discover an intermittent connection problem in a 12-volt feed circuit that breaks down when stressed by high current flow. When the poor connection manifests under electrical load, it drops the voltage applied to regulator wire #2, and the regulator boosts output voltage to compensate. Pay particular attention to where the #2 regulator wire ties into the main harness.
Trace both regulator wires as posted previously. Report back with what you find.
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Meant to say BD.... typing on phones ain't a good thing.lol I'm good.
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Bd I'm thinking the same as what you said. Tomorrow after work I'll chase some wires and clean connections. This has got me stumped...
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Forgot to say this is also my second starter. I've kept a tab on things changed. :-)
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These wiring references will be your best friends if you refer to them regularly: the 1983 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST386_83_1983_GM_Wiring_Manual_CK_P_G_10_to_30_and_ST.pdf) (page 9) and the more generalized 81-87 Wiring Diagrams (http://forum.73-87chevytrucks.com/smforum/index.php/topic,11766.msg87585.html#msg87585). The 1982 Wiring Manual is missing from our library.
Circuit 25 (brown) is the #1 regulator resistance wire to which I referred (look at the diagrams for an illustration of where the wire should be routed). Circuit 25 is the 'exciter' lead that turns the regulator ON initially with ignition power. It's not likely your issue is with this circuit, but you need to verify where it connects, nonetheless.
Circuit 2G (red) is the #2 regulator wire that should connect directly to the starter through a fusible wire. The #2 wire is the 'sensor' or feedback lead the regulator uses to adjust alternator output. If not a ground, the culprit is most likely in this wire or between the starter and battery, hence, zieg's early post to verify battery cable condition/connections.
To resolve your issue as efficiently as possible, try to avoid making any assumptions.
Once you correct the actual fault, I'll provide an upgrade to a more effective design that will help alleviate this type of problem in the future.
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on your battery whats that alligator clip for?
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Fan motor I thought going straight to the battery would help.it did help a little
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How new are your battery cables?
Idk I guess I could ohm the positive wire
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Don't measure cable resistance; do a voltage drop test! Voltage drop tests are dynamic tests. Resistance checks are static tests. Your ohmmeter isn't sensitive enough to correctly register the small resistance that could cause an operational problem in a high-current circuit. Whereas, measurable voltage loss across a cable is a dead giveaway. Resistance measurements have their uses, but are best suited to low-current circuits.
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Volt drop test it is
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I noticed the positive Batt wire sits real close to the engine block. Maybe it's heated a gone bad. It don't look that old at all
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As a sidebar:
Copper is unaffected by the heat radiated from an engine, although ozone, heat and chemicals can attack the insulation. Damage to copper cables is usually a result of battery acid wicking down the cable or salt wicking up-cable from the starter - the result is very green and the cables become rigid with salt buildup inside the jacket. :)
If the cables are original GM, they may be copper-clad aluminum. Aluminum cables gradually increase in resistance over time and should be replaced with solid copper cables when service becomes necessary due to voltage loss across the cables.
IMO - The best choice for most of our trucks is 1 or 0 all-copper stranded cable with terminal ends tightly crimped, soldered and shrink sealed.
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just curious but whats the reading on the signal wire to the alt? when its not overcharging and when it is
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Sorry for the delay. Family first ya know. BD and zieg now I think about it I sent my starter back to summit, cause I thought it wouldn't start my truck, so it may just be the Post Batt wire to the starter
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I'll get some readings thurs my day off. Thanks guys
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Sorry for the delay. Family first ya know. BD and zieg now I think about it I sent my starter back to summit, cause I thought it wouldn't start my truck, so it may just be the Post Batt wire to the starter
I've found my fair share of really good looking green corroded wire in amongst the bright red insulation. The least little bit of starter drag, or charging issues I automatically check my engine to cab and engine to frame grounds and if are sound I put a new positive cable on it. For no more than they cost it is a good practice if they have any age on them at all. I'd say a good 90% were green with corrosion... 1 or 2 were alternators, a couple were dragging starters and 1 had a bad cell in the battery. Funny thing it started the car fine but all kinds of issues cropped up... This is from 20+ years and 300+ cars and trucks...
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Sounds about right. Thursday I'll check and change the + Batt write and alternator charging wire. What sizes do you guys recommend?
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Sounds about right. Thursday I'll check and change the + Batt write and alternator charging wire. What sizes do you guys recommend?
For the battery cables:
... IMO - The best choice for most of our trucks is 1 or 0 all-copper stranded cable with terminal ends tightly crimped, soldered and shrink sealed.
For the alternator charge lead:
... If the alternator is rated less than 70 amps output, build the charge lead from 8-ga wire; between 70 and 100 amps output, use 6-ga wire; between 100 and 150 amps output, use 4-ga wire; over 150 amps out, use 2-ga wire. Protect the charge lead with 6" of the appropriately sized fusible wire at the charge lead's battery connection. Crimp then solder all terminal ends....
Route the alternator charge lead directly to the battery through a 6" length of fusible wire at the battery end. How to make a Fusible Link (http://forum.73-87chevytrucks.com/smforum/index.php/topic,11972.msg45217.html#msg45217).
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Thanks a lot!
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Thick or thin stranded wire?
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Thick or thin stranded wire?
For the battery cables, thin stranded wire is welding cable. Welding cable is expensive and unnecessary unless you need flexibility along the length of the cable run. Welding cable is great for jumper cables - overkill for stationary wiring. On the smaller cable I think it amounts to personal preference and what's available.
However, I recommend using SXL or GXL insulated primary wire, because it is significantly more resistant to heat and underhood chemicals, ozone, etc.
I neglected to mention earlier, run the #2 regulator lead directly to the output post of the alternator.
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Sounds like a game plan now I'll have to check the parts stores for the wire
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Most parts houses won't carry SXL/GXL wire, because it's more costly and many techs don't know the difference. GPT or PVC thermoplastic insulated wire may be all you'll find. But, you can order SXL/GXL: Del City (http://www.delcity.net/store/Wire-&-Cable/) or Terminal Supply Company (http://terminalsupplyco.com/Store/Default.aspx?CAT=GXL&PCAT=77017#Categories), etc.
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Ok I'll try and find a place that sells the cable by the foot or in five foot sections. So far idk...
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Most parts houses won't carry SXL/GXL wire, because it's more costly and many techs don't know the difference. GPT or PVC thermoplastic insulated wire may be all you'll find. But, you can order SXL/GXL: Del City (http://www.delcity.net/store/Wire-&-Cable/) or Terminal Supply Company (http://terminalsupplyco.com/Store/Default.aspx?CAT=GXL&PCAT=77017#Categories), etc.
Hey y'all I ended up just getting the welding cable #1 and I had 4 gauge power wire around to use for the alternator charging wire. I'll take pics in a few
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Good news and bad...good-wiring and and charging issues solved :-) thanks to all. Now the bad. As I embark on my 3 mile test ride AC ah blast. I notice the truck stats to run ruff........ Kinda likes can love went flat :-(
good I get it back to the house. Turn it off pull the valve cover and no flat lobes :-) hooray. . IM gonna pull the plugs and check. I when on my trip I pulled over to a gas station and noticed white/blue smoke coming from the pass side tail pipe. . When I started up after getting back to the house turf running and smoke were gone. Idk one thing or another
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Ok all is well guess I never connected one of my spark plug wires all the way and bumped it loose while putting the new wires on today. Now one more issue. Flickering head lights and dash lights.. New head light switch in from day one of the build. I've got my ground covered idk on this one any ideas? Thanks y'all
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...Flickering head lights and dash lights....
Any more details? When did it start?
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Kinda happened over time. I just thought it was related to the charging issue. Is there supposed to be a ground wire of the head light switch? Or some where close by.I've searched but nothing good yet
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when does this happen? idle or driving? do you notice a voltage drop when this happens?
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The headlamp switch grounds through its frame connection to the dash, but that ground is just for the dome lamp. Do the headlights and dash lamps flicker in unison?
Connect your voltmeter between the alternator output post and ground to measure the voltage as the lights flicker. Is the voltage fluctuating, too?
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Yes they do flicker in unison I'll check the alternator tomorrow. My truck is loud very loud :-)
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Check the alternator voltage under the same electrical load with the headlights ON and flickering. Where did you tie the charge lead and #2 regulator lead into the vehicle wiring?
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Ilk check the voltage on lunch break. I haven't tied the regulator wire it onto the charging post yet.but will do
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Volt drop is .02 across the charging wire from the alternator
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...Connect your voltmeter between the alternator output post and ground....
You need to determine if alternator output is fluctuating, so measure the output voltage while the lights are flaring.
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Alternator voltage is fluctuating between 13 and 15.3 under load. I tired the reg wire to the charging post. Still the same thing. . Some reason I'm thinking it's a ground issue idk
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Sorry that reading was from the Batt terminal.
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Alternator voltage is fluctuating between 13 and 15.3 under load. I tired the reg wire to the charging post. Still the same thing. . Some reason I'm thinking it's a ground issue idk
So, measured at the battery, output voltage fluctuates between 13 and 15.3, using the headlights for the load. The alternator's 4-ga charge lead is connected directly to the battery positive post, and you connected the regulator #2 wire to the output post of the alternator. Correct?
Measure alternator output voltage directly at the alternator output stud. Connect a temporary jumper between the alternator case and the negative post of the battery. Any change?
Do you have an inductive DC ammeter module for your Fieldpiece meter?
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(http://img.tapatalk.com/d/13/08/17/udu8a8eg.jpg)
At the alternator
The voltage fluctuates from 13.8-14.5.
Tried the jumper to the alternator case no change
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This time around I drive 17 miles and the readings I just posted were the results at both Batt and alternator
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Alternator voltage is fluctuating between 13 and 15.3 under load. I tired the reg wire to the charging post. Still the same thing. . Some reason I'm thinking it's a ground issue idk
So, measured at the battery, output voltage fluctuates between 13 and 15.3, using the headlights for the load. The alternator's 4-ga charge lead is connected directly to the battery positive post, and you connected the regulator #2 wire to the output post of the alternator. Correct?
Measure alternator output voltage directly at the alternator output stud. Connect a temporary jumper between the alternator case and the negative post of the battery. Any change?
Do you have an inductive DC ammeter module for your Fieldpiece meter?
I did connect the #2 reg wire to the Batt out post on the alternator.
The alternator's 4-ga charge lead is connected directly to the battery positive post, and you connected the regulator #2 wire to the output post of the alternator. Correct? Correct sir just like you say :-)
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Is the charge voltage constant or fluctuating at constant engine RPM?
If it's fluctuating, it sure sounds like a regulator issue or connection issues inside the alternator. A properly functioning solid state regulator should stabilize voltage output at about 14.5 volts. It may have been damaged when it went full field. What kind of warranty do you have on your alternator?
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Although there still could be a wiring problem, you may have to take systematic voltage drop measurements to find it. Best approach would be to pull all the fuses again to eliminate all fused accessory circuits. Could prove quite tedious. Frankly, I would start with the alternator.
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Honestly my thoughts are as yours. I figured it was damaged by the old battery cable. I'll cut open the old battery + wire tomorrow. I just bought the alternator a fee months back... ButThe thing that sucks is I bought it from Orielys AV BD know they will put it in the tester and say it's still good. I'll have them test it under extreme load while it's in the truck. Got any ideas on how this thing can go bad quick with out causing a seen at the parts store? I'm game :-)
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Is the charge voltage constant or fluctuating at constant engine RPM?
Yes you can hear it clear with my loud pipes :-) if I had a tach(it burnt out due to this issue... It would fluctuate as well. Burnt out as in I smelt it and clipped the writes going to it. Not grounded out. It just couldn't handle the high volts going to it.
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Well it tested good so I'll have to try buying a new one. Other wise evenings good
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There is quite a lot to read through here, is this still an active post and is the problem still presently the same problem as your first post?
If yes, what year is your truck? and does everything running through the fues box lose power when the problem happen?
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Voltage spike is gone. Thanks to these good guys. Nothing lost power inside.. Just saving for a good name brand alternator at this point