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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: lilkiduno on June 10, 2019, 12:22:53 AM

Title: Accessory Power Issues
Post by: lilkiduno on June 10, 2019, 12:22:53 AM
1984 C10 305 with gauges.

Okay guys,

I am attempting to hunt down an issue my truck had began doing. I was driving home and all a sudden my Choke light illuminates. I knew it was something that needed addressed, however I had other things going on and it got back put on the back burner. Now I am trying to track down the issue, now that it's not raining like crazy. After the choke light I noticed the Volts gauge was reading too high, Higher than was I thought was normal, just below the 15 mark, I thoughtto myself the alternator puts out 14.6 if i remember correctly, no big deal. Turns out I went to step on the gas and my radio dies, look at the volt meter again and it's over the 15 volt reading, under acceleration it increases, got over 15 volts and it shut my radio off, bring it back to idle and it gets below 15 volts the radio come back on. Okay, that had to be alternator, well take it to get tested, the machine at oreilly's reads bad on all the tests, resistors regulator and the third test, can't remember what, all failed. Purchase a new alternator and install, the voltage on the gauge appears correct. Choke light is still on, I have no power windows, no blower motor. I don't know if these are connected, but when I try to use these accessories (windows and blower) the choke light illuminates brighter. Checked fuses at the choke and gauges, both okay, will check fuses for windows and blower tomorrow. I am looking at the wiring diagrams lost in lines and am hoping someone may have some insite. I know I need to check the fuses tomorrow and I will. Just with the summer weather approcing power windows are becoming a must and any help would be appreciated.

Oil pressure gauge dosen't work, replaced the oil pressure switch because I read it could be out.
Title: Re: Accessory Power Issues
Post by: 75gmck25 on June 10, 2019, 05:33:49 AM
Its most likely that you have a ground wire broken or loose, and those circuits are finding a ground path when you turn on other accessories.

Grounds to check:
- Large ground wire from battery to alternator bracket; use star washer and make sure its a good solid connection
- Small ground wire from battery terminal to firewall
- Ground on each side of firewall from the headlight wiring
- Ground from engine to firewall.  Often connected to a bolt on the back of the engine on passenger side, or a bolt on the valve cover.
- Ground from frame to engine, usually down low on the passenger side near the fuel pump
- Instrument panel ground up under the dash. Might be connected to a post on the emergency brake, or on newer trucks to a ground bus up under the dash
- Large ground wire in back of the truck wiring about in the middle of the bumper, and a smaller ground wire for each taillight.

There may be others for specific accessories.  For example, the choke sensor (on the oil pressure switch?) may have a ground on one side that is now disconnected or not making a good connection to the engine.

Bruce
Title: Re: Accessory Power Issues
Post by: bd on June 10, 2019, 04:38:45 PM
As suggested by 75gmck25, verifying all grounds is a prudent starting point. 

Avoid star washers for ground connections and especially for battery cable connections.  Star washers can allow moisture intrusion to the connections, which exacerbates corrosion.  In addition, they decrease the surface area of direct metal contact.  Rather, burnish metal at the attachment site until it is bare, clean and shiny.  Make sure that ring terminals are properly sized to the bolt used to attach them.  Then liberally coat the terminal and attachment point with antioxidant during assembly. 

Never connect the engine-to-firewall ground strap to a valve cover bolt.  Attaching to a valve cover bolt will invite grounding trouble for all cab appliances.  Instead, attach the ground strap under a 3/8" bolt at the back of the passenger side cylinder head.

The Choke light grounds through the choke thermostat heating element.  See the technical article, GM electric choke operation for Q-jet carbs (http://forum.73-87chevytrucks.com/smforum/index.php?topic=36868.0) for details on function.


The following inventory of 1973 - 1987 (91) GM truck grounds is excerpted from the technical article, Vehicle Ground (http://):

Whether you are experiencing electrical problems or refurbishing the vehicle, take an inventory of all of the vehicle grounds and service them appropriately (disassemble and clean connections to shiny bare metal, followed by liberally coating terminals and connections with moisture rejecting antioxidant paste).  Upon inspection you should discover the following vehicle grounds; recommended wire sizes are listed for any ground paths that need to be fabricated and installed:
Additional primary ground connections are okay.  If any of the recommended ground connections are missing, fabricate and install them!  If damaged, repair or replace them!


Other areas to check are the fusible links and harness connections at the starter and firewall junction block.  Loose connections or compromised fusible links can cause "mysterious symptoms."

Title: Re: Accessory Power Issues
Post by: lilkiduno on May 12, 2020, 03:44:47 PM
Sorry for the delay. It took way longer to get around to this. I know this is old, please bare with me. I checked the primary grounds from the battery to the frame and rad support, sanded them until clean metal was visable and tossed the star washers. The Ground strap from the rear of the cylinder head appeared to be good and in tact, I didn't pull the strap as I didn't get around to it before postponing again. The Ground in the cab appears to be a good connection as all the gauges and lighting appear to be working (except the oil gauge, still have not replaced the sender.) I have power at the juction box on the firewall, tested with a multimeter some time ago.

Pulled put my test light today at break, as I still have not tracking down the issues from above, I have no power at the relay (I assume relay, small metal box) with the key on. Where would the fuse box be supplied it's voltage for the power windows. Still don't have heating/cooling, but I am more worried about the windows for now. It appears I have a red/pint wire shoved into the fusebox wheer the window relay goes, I will back trace it to see where it goes. Had to get back inside. 
Title: Re: Accessory Power Issues
Post by: bd on May 13, 2020, 01:43:44 PM
Windows are powered from the WDO cavity near the top of the fuse box and are protected by an adjacent 30-amp circuit breaker.  The circuit receives ignition voltage only when the ignition switch is in the Run position.
Title: Re: Accessory Power Issues
Post by: lilkiduno on May 14, 2020, 12:20:22 PM
So is this pink wire suspose to be there then, just under the circuit breaker?

https://imgur.com/70J2KcE
Is it okay to run a jumper wire from 12 volt to the pink wire to the window switch? Sorry, I was waiting for a response before I went down the rabbit hole with incorrect direction.

Title: Re: Accessory Power Issues
Post by: bd on May 14, 2020, 01:14:28 PM
Is there power on both sides of the 20-amp fuse located at the top of the fuse box above the pink wire with the ignition switched on?
Title: Re: Accessory Power Issues
Post by: lilkiduno on May 14, 2020, 02:07:33 PM
Are you asking about the 20 amp heater fuse above the circuit breaker? If so, no there is no voltage there either. I don't have my Multimeter and am currently using my test light, loaned my multimeter to my cousin.
Title: Re: Accessory Power Issues
Post by: bd on May 14, 2020, 02:19:01 PM
For this type of diagnosis, a test light is the better tool anyway.  With the ignition switched on, check for power on the 12-gauge orange wire as it exits the ignition switch.  If the orange wire is dead but the pink wires have battery voltage, replace the ignition switch.
Title: Re: Accessory Power Issues
Post by: lilkiduno on May 14, 2020, 02:51:49 PM
I know it may sound dumb, But is this something I should drop my steering column to get to?
Title: Re: Accessory Power Issues
Post by: bd on May 14, 2020, 03:40:25 PM
Yes.
Title: Re: Accessory Power Issues
Post by: lilkiduno on May 27, 2020, 12:26:06 PM
Sorry for the delay, just finished testing the orange wire socket, is it normal for this socket to have two wires connected? Sorry I didnít snap a picture, I can drop the column again for this photo if necessary. 

Also, I had what appeared to be three pink wires on my ignition switch, two of which were hot without keyed ignition and the throes was hot with keyed ignition. But the two orange wires were receiving power once the key was turned to the run position
Title: Re: Accessory Power Issues
Post by: bd on May 27, 2020, 06:28:05 PM
The ignition switch has two 12-gauge red wires (B+ - power from battery), one 12-gauge pink wire (IGN - power to ignition), two 12-gauge orange wires (IGN 2 - ignition powered accessories), one 12-gauge yellow wire (SOL - engine crank), and one 12-gauge brown wire (ACC - power to accessories).  Various other colored wires may connect to the ignition switch depending on the application (e.g., brake warning test, engine temp test, alternator).  This how the ignition switch terminals should measure:

B+ - constant 12 volts

IGN - 12 volts in crank and run positions

IGN 2 - 12 volts in run position only

SOL - 12 volts in crank position

ACC - 12 volts in accessory and run positions

Check the circuits with the wires connected to the ignition switch in its various key positions.  If wires measure 12-volts when they should be dead, unplug the ignition switch and retest the wires in the two connectors.  Only the two red wires should measure 12 volts with the connectors disconnected from the switch.

Report back.
Title: Re: Accessory Power Issues
Post by: lilkiduno on May 28, 2020, 12:59:41 PM
I won't be able to test this today as it's been raining today. However, I didn't pull the connectors from the switch and just tested the backside when I tested with the test light yesterday. The lighting wasn't great so that's what I said three pink wires, I am sure they're propbably red vs pink. I do know the Orange wires were receiving power with the key switched on as tested with the test light.
Title: Re: Accessory Power Issues
Post by: bd on May 28, 2020, 01:58:33 PM
The choke and heater fuses as well as the power window circuit breaker, all located at/near the top of the fuse box, are powered by the two 12-gauge orange wires from the ignition switch.  With the ignition switched ON, if the orange wires measure 12 volts where they exit the ignition switch and the CHOKE, HTR & WDO fuses/circuit breaker test dead, check the orange wires behind the fuse box where they crimp onto the fuse box terminals - make sure they are not burned or corroded.  If the connections to the fuse box are fine trace the orange wires back toward the ignition switch to locate and repair the open.
Title: Re: Accessory Power Issues
Post by: lilkiduno on May 28, 2020, 04:34:43 PM
So, I should have power to one side of the circuit breaker if the breaker is bad right? Otherwise how do I remove the Fuse panel to check the back side, Unbolt the one bolt in the engine capartment and then should it pull off on the inside? I won't be able to work on it tonight and maybe not for the nest few days, They're calling rain for the next few days. Just trying to get a game plan
Title: Re: Accessory Power Issues
Post by: bd on May 28, 2020, 05:47:52 PM
So, I should have power to one side of the circuit breaker if the breaker is bad right?

Yes.  In the Run position only.


How do I remove the Fuse panel to check the back side, Unbolt the one bolt in the engine capartment and then should it pull off on the inside?

You will need to leave the engine compartment harness plugged into the bulkhead connector since that is how power enters the cab from the battery.

From inside the cab, remove the two screws (yellow arrows in the upper image) that retain the fuse box to the firewall.  By removing the two screws, the fuse box and bulkhead connector will loosen from the firewall but will not separate from the firewall entirely.  Next, simultaneously pry the two plastic clips located on the lower flanks of the screw bosses (green arrows in the lower image) outward just enough to unclip the fuse box and work it away from the firewall bulkhead connector by rocking and pulling the fuse box toward you.  A long narrow screwdriver works best to dislodge the clips.  Don't pry the clips outward too far or you will risk distorting them permanently.  This action will separate the fuse box from the bulkhead connector.  Rotate the fuse box to access the wire connections on the backside.

Title: Re: Accessory Power Issues
Post by: lilkiduno on June 03, 2020, 10:54:09 AM
UPDATE: I had a few moments to look at it yesterday There was no prower to either side of the circuit breaker so I seperated the fuse block. It was fairly hard to see up top, However, it didn't appear to be burned or corroded that I could see, Since I was doing this again on a 1/2 hour lunch break, so I didn't have time to drop the column again the trace the orange wires, This is obviously the next step and hopefully the issue. I hope to have this hammered out before but this ishould be done by the end of next week at the latest as a lot of attention has been perpairing for a family vacation, where I have to stay behind and work, so I will have much more free time once everyone is gone, I guess that sounds pretty selfish.
Title: Re: Accessory Power Issues
Post by: bd on June 03, 2020, 04:12:26 PM
Keep in mind that IF there is power on the orange wires at the ignition switch, it should occur ONLY with the key in the Run position.  IF there is power on the orange wires at the ignition switch with the key in the Run position but no power through the orange wires to the fuse block, then the orange wires are open somewhere in between.  On the other hand, if the orange wires are dead at the ignition switch, either the ignition switch is faulty or the switch terminals are not making connections with the wire terminals in the harness connector.  Make sure the switch terminals are not bent so that they won't engage the connector terminals.
Title: Re: Accessory Power Issues
Post by: lilkiduno on June 04, 2020, 12:18:59 PM
bd, Thank You so much for all your help. I went to trace the orange wires, unwrapped the loom pulled the orange wires to seperate them and trace them, plug pulled out of the ignition switch, pushed it back in and heard the click, tested, that was the problem, Simple but effective, power windows work, blower motor blows and choke light is off. Thank You!
Title: Re: Accessory Power Issues
Post by: bd on June 04, 2020, 03:21:54 PM
The two connectors that engage the ignition switch interlock and must be connected to the switch in a specific sequence.  If the sequence is reversed one of the connectors won't fully engage the switch terminals.  Double-check to ensure that both connectors are fully plugged in and seated.
Title: Re: Accessory Power Issues
Post by: lilkiduno on June 05, 2020, 07:38:42 AM
I will drop the column again and check today, I did however give it a backward tug and it didnít pull out. However, with as easy as it is to get to Iíll just be sure to double check.