Electrical: Warning lights fail to light at ignition-on

Joined
Aug 20, 2016
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5
Location
Georgia
Electrical gremlins.
With ignition switch in "On" position, the warning lights for charge and brake ( hand brake down/off) and seatbelt do not light. The seatbelt buzzer does beep. Dash voltmeter indicates < 11V when engine running. Concurrent with these symptoms, engine fails to idle.
Alternator ( Rockauto, internal regulator) is new-ish ( several months). At the fuse terminal for the charge lamp, there is no current with key in "On" position. I removed and lightly sanded the metal insert on the white MPC near the fusebox. I eyeballed the actual ground point ( the one by the mounting bolts for dash); there was no obvious corrosion.

Help?
 

OSS

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Jun 30, 2017
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All those indicator lamps share not only a common grounding spot but a common mini-buss connector that joins them all together then routs it to a ground location under the dash on the driver's side A pillar.

This thread linked below has more info about it and a possible place to start looking.

The mini-buss common grounding junction often fries on these old trucks, creating resistance (or no circuit) to ground



image.png
 
Joined
Aug 20, 2016
Messages
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Location
Georgia
The mini buss common ground, I believe I removed the metal strip and lightly sanded it. It wasn't particularly funky. The common ground that it feeds to at the dash frame I eyeballed only. It seems clean.
 

OSS

Joined
Jun 30, 2017
Messages
2,681
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So if their ground is good, the source is not.
They're fused through the Engine fuse and triggered by the ignition relay, Maybe check out the function of that relay.

Also assuming that the bulbs are good... unlikely they'd all burn out at the same time.

image.png
 
Joined
Aug 20, 2016
Messages
5
Location
Georgia
Diagnosed.
The fuse for "engine" . 10A, slot 7 by the OManual.
Keep It Simple Stupid and don't assume.
I assumed that it fed the ignition ( NOT) and was good bc the engine ran, albeit poorly. Visual inspection of the fuse did not detect break.
Multimeter did reveal break. By that time, I'd reinstalled the IG relay in the empty slot, lol. I dropped the relay dock/ bracket, noticed my misreplacement. Restored relay. I looked more carefully at the schematic and realized the engine ran w the fuse blown bc the fuse doesn't feed the IGNITION/coil ( my erroneous assumption). It DOES feed the ignition relay though.

Thanks, y'all. My first post. Thanks for all the work y'all have done here for years.
Fair winds and cheap gas,
David
 
Joined
Aug 20, 2016
Messages
5
Location
Georgia
Diagnosed.
The fuse for "engine" . 10A, slot 7 by the OManual.
Keep It Simple Stupid and don't assume.
I assumed that it fed the ignition ( NOT) and was good bc the engine ran, albeit poorly. Visual inspection of the fuse did not detect break.
Multimeter did reveal break. By that time, I'd reinstalled the IG relay in the empty slot, lol. I dropped the relay dock/ bracket, noticed my misreplacement. Restored relay. I looked more carefully at the schematic and realized the engine ran w the fuse blown bc the fuse doesn't feed the IGNITION/coil ( my erroneous assumption). It DOES feed the ignition relay though.

Thanks, y'all. My first post. Thanks for all the work y'all have done here for years.
Fair winds and cheap gas,
David
......and the idle is restored.
 
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