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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: EvilleIron on August 31, 2009, 06:32:08 pm
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Hi,
Im new here, and I have a big problem.
My truck is stuck at work.
About a week ago my starter key got stuck on and has been messed up since.
So far, the alternator has been replaced, the control module was too.
Also the key cylinder.
Auto zone tested the starter, ign coil and module, coil was ok. He said the starter was using alot of amps, but works.
After doing all this, I checked the contiuity to the pos battery cable, the alternator + and plug, and the coil +.
and it buzzed.- not good.
I did not put the battery in after checking and replacing this stuff.
I'm no mechanic, but Ive worked on this truck for years.
Any Ideas of what else to check. Thanks.
It's a 76 C30 2wd SRW Custom Delux, with no ac or cruise or nothing.
Very simple truck- usually.
Brian
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You cannot ohm a live circuit. I'm not sure what you were even trying to accomplish by doing that.
Why don't you start over and tell us what your truck is doing. Will it not crank the starter motor?
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Hello VileZambonie
Sorry if I wasnt clear.
My truck shorted somewhere, I think.
I used a Fluke voltmeter with continuity buzzer.
The battery is not in the truck. The pos terminal/wire is resting on the plastic wash tank.
I got continuity between the positive battery cable and chassis.
I got continuity between the pos alternator and both prongs in the plug to chassis.
I got continuity between the hot wire from the coil to the chassis.
I'm terrible at electrical, but I dont think this is right, so I havent put the battery in.
It's as though the positive battery cable was grounded, unless Im missing something and did something wrong, but I dont think so.
When it first happened, and I replaced the alternator, When I went to put the battery in, it arced like when jumper cables are crossed. It fried the new alternator. I now have a 2nd replacement alt.
Today I pulled the coil and module, and the module was also fried.
I put it all back in and tested the continuity again before deciding not to put the charged battery back in.
It still has continuity in all those places to chassis. Is it supposed to?
Thanks for the reply.
Brian
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If it's connected you WILL have continuity. Now check your fusible links and if they are ok put the battery back in.
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ok, thanks.
The parts are installed, except the battery.
I'm just not understanding why open positive wires would buzz with the chassis on the tester.
Maybe a rubbed wire.
Brian
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It doesn't mean it's open. Just because the source voltage isn't present you have not opened the circuit. A mechanical switch for example opens a circuit. If you check the B+ side of the fuse and to it's ground you will have continuity. The circuit is powered off so your continuity test is useless unless you are tracing an isolated circuit. Check those fusible links first. Do you know where they are?
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I cant recall from memory where they are, but I know what they should look like.- I'm working on a couple of my trucks presently.
Thanks for the help. I'll get back to it tomorrow.
Just paranoid to fry something(s) again.
Brian
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Look down by the starter motor where the B+ cable connects and look at the junction block on the firewall.
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Thanks, everything looked fine and I put the battery in.
There was no arcing this time, but the voltmeter is reading higher at higher rpms.
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You cannot ohm a live circuit. I'm not sure what you were even trying to accomplish by doing that.
Why don't you start over and tell us what your truck is doing. Will it not crank the starter motor?
Ruin his voltmeter maybe?
Although a small voltage like this and DC nonetheless probably wouldnt destroy it. Still not a good idea
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You cannot ohm a live circuit. I'm not sure what you were even trying to accomplish by doing that.
Why don't you start over and tell us what your truck is doing. Will it not crank the starter motor?
Ruin his voltmeter maybe?
Although a small voltage like this and DC nonetheless probably wouldnt destroy it. Still not a good idea
Fluke meters are top notch, and have built in safety measures to protect the meter from damage. When checking for shorts, I use the ohm setting to check the resistance that way. Sometimes the beeper will go off on acceptable readings. The best way for me is to set the meter between the pos and neg, and start disconnecting components until I see a substantial change. Its also best to check amperage draw on the systemwith the key off, but not everyone has access to that type of meter. You'll know real quick if there is a drain because the battery wont last long
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Ohming or checking continuity of a circuit is nearly pointless unless you isolate the circuit. Checking continuity through wires will easily mislead a novice because you will have continuity through devices that should have continuity. People instantly assume this means a short to ground which is not necessarily the case.
Checking amperage draw using your meter (non inductive) you need to break the circuit and install the meter in series or your meter will become the load in the circuit. Your hand held meter won't take 600A :o so be careful. If you are checking ESD sensitive components best stay away unless you know what you are doing with that meter.
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What was the original problem? Did the key stick in the start position and crank? Or did you let the key go and did it crank?
What does the voltmeter read that has you worried?
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Thanks all,
I dont know whats going on with it.
Marc, yes the starter got stuck on in the on position.
That may be attributed to a worn key cylinder that would take almost any old square gm key.
so far, the key cyl, alternator (X2), control module and now the starter have been changed.
The starter is a spare, but I tried to run it with the previous one
and thats when I suspected the old starter. Thats when I think I fried something again.
'shoulda changed it before I put the battery in, if it is fried.
Anyway it runs- poorly- I drove it 10 miles home with 1000lbs of veg oil in the bed.
The hi voltmeter reading I mentioned is the truck's ammeter in the dash.
It overcharging. It used to always be right on 13.
After the weekend it was re-assembled, the battery was stone dead.
I charged it all day and got it home - somehow. 10 miles. and it restarted right away when I shut it off in the yard.
I never put any meter to it while the battery was in it.
I was trying to the best of my limited electrical ability to find a short in the wiring.
And the reason I'm writing this today is because I dont have experience with diagnosing electrical problems.
I live pretty close to an AdvanceAuto, and will limp over there to get free testing. I also got both alternators there.
Brian
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Lets refresh a little and start over. What are the symptoms now? You said it was overcharging, what is it charging at right now? Lets see what its doing now, and start over so we can see if we can help.
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Hi,
Choptop, I was just scanning the forum archives for similar problems and just finished reading one from October that you helped someone with.
This should be simple, the truck is just a motor and a muncie. hydro brakes.
I mean it has the wiring of a hot rod. No options what-so ever.
I'll get back to you tonight after work, but here's where I'm at.
Tuesday it had to be charged to start and fired right up fine.
The voltmeter in the truck is reading 25% past 13v.
I didnt do any more readings since I put it all back together.
I drove it home without using any electrical things like lights/radio in case the battery was carrying me.
I'll try to start it this morning and put it on the charger for the day if need be.
TIA
Brian
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I have to be honest, but Im not very good at estimating the voltage on the gauges of our trucks. They are a good reference,but nothing else. When you get a chance, take your Fluke as see what the battery voltage is when its running. If you can get a measurement before you start it (if it will start) that may also tell us something. If the battery is low, then its normal for it to charge hi until it reaches full charge. but something is still draining it. What model fluke do you have? I may be able to tell you how to check for amperage drain with it. If your not getting the spark that you previously have when you connected the battery, you may have a bad battery. Anytime you drain a battery down to where it wont do its job, you cut its life in half. So depending on how many times this battery has been dead, it may be going out completely real soon. Let us know.
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I'm at work, now.
It did start this morning after sitting 2 days, but I could tell it was losing charge.
The fluke T3 is just an led voltage tester (up to 480v), with continuity tester.
I also have mutimeters of different brands.
I'll get back to it tonight after work, thank you.
Brian
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The truck started when I got home, just fine.
The voltmeter of the truck is still over 13v.
the truck just sits most of the time, till I haul heavy stuff.
Now it feels like it needs a complete tune up.
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As of yesterday, all of the electrical, starting and charging parts have been replaced.
The voltmeter in the dash is still high.
I think I have a rubbed wire somewhere to chassis.
I did the plugs and wires, cleaned the carb and it runs very strong again.
Thanks for the help.
Brian
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What does your hand held meter tell you?
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Agreed, Id like to know exactly what voltage is getting to the battery before you go any further. You may be ok.
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the continuity could be coming from the radio or something like that the voltage could be just like chop said the gauge could be wrong.
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Thanks for all the help.
I took it to a friends shop and he did all the testing and also changed the ignition switch on top of the column.
He found a relay that was very hot to the touch. It's a blue plastic covered cube relay.
Upon opening it up, the relay was burnt. I have no idea what the relay goes to.
The truck is pushing 14v while idling. everything is working as before.
The only thing the truck has that is not stock, is the wiring for a 2way radio like a commercial motorola.
I dont know what the problem is or was, but Im glad its working.
Now I can work on my '96 K2500TD -again.
Brian