Instrument panel light question

[Chris64]

I've rebuilt the instrument panel with a new housing and new speedometer. This whole project started with almost no dash lights working.

I replaced all the bulbs and the only one I couldn't get resolved was the right blinker in the dash (the outside lights are blinking).

100% the cluster is working when I put power directly to the correct wire.

While it was unplugged I tested the left and right - the issue seemed to be there was no signal on the harness (dark blue wire, light blue is left). This is very weird since the outside blinkers are working fine. I removed the fuse panel and inspected everything on both sides of the firewall and surprisingly it didn't look bad.

Anyway I took it for a spin to test the speedo and suddenly the right blinker start working...then it didn't...then it did.

To add to the oddities, if I turn on the headlights, the right blinker light comes on until I turn on the right blinker on where it will go off and then sometimes blink. Keep in mind it's always working flawlessly outside and the flasher is clicking.

It's tough to test at the fuse because I need to unplug it from power. I'm hoping this will sound familiar to someone. All the wiring is very stock with no mods or splices which is nice and unusual.

 

[Jgonick]

To add to the oddities, if I turn on the headlights, the right blinker light comes on until I turn on the right blinker on where it will go off

It is getting back feed from the parking lights (not uncommon)- usually a ground issue. I always start by checking grounds. Check your grounds inside the cab. Also check grounds at front right turn signal & head lamps.

Are you using LEDs or incandescent bulbs?

 

[75gmck25]

It is almost certain to be a ground issue. When a ground is bad, devices “find” other paths to ground, and lights go on and off.

Did you securely attach the instrument panel ground wire ( its a separate black wire, not the big multi-wire plug) to the post on the parking brake mechanism? If you did, then verify the post is grounded through the bolts holding the brake mechanism to the body.

 

[Chris64]

It is almost certain to be a ground issue. When a ground is bad, devices “find” other paths to ground, and lights go on and off.

Did you securely attach the instrument panel ground wire ( its a separate black wire, not the big multi-wire plug) to the post on the parking brake mechanism? If you did, then verify the post is grounded through the bolts holding the brake mechanism to the body.

I did not see an instrument panel ground wire...hmm. It's just a harness and the speedo cable and the oil line. I did see a wire grounded to the parking brake bracket so I'll chase it down.

 

[Chris64]

It is getting back feed from the parking lights (not uncommon)- usually a ground issue. I always start by checking grounds. Check your grounds inside the cab. Also check grounds at front right turn signal & head lamps.

Are you using LEDs or incandescent bulbs?

ok, now I need to add more detail. It's all incandescent and every bulb has been replaced in the entire car except the front right blinker. I'm not sure if that bulb not being in place could be causing this problem.

 

[AuroraGirl]

ok, now I need to add more detail. It's all incandescent and every bulb has been replaced in the entire car except the front right blinker. I'm not sure if that bulb not being in place could be causing this problem.

it should cause your right side to blink faster if its not hooked up (The front facing one that is) unless you have a timer based can not a heat/thermal one

 

[Jgonick]

I'm not sure if that bulb not being in place could be causing this problem

Possibly- It is a dual filament bulb and the side marker (right turn signal) actually grounds by going through the bulb.

I'll try to explain what is possibly happening. As you know, electricity come from the positive side of battery and has to return to the neg side.(conventional) The return path uses grounds (uses the metal of the car) to get back to the battery. electricity is lazy- it will take the easiest path back to the neg battery. So if you have a weak ground-you can think of it like plumbing with a partial clog. A little water everything works fine, however if you add to much water it backs up. Once it backs up it looks for another way back. If it finds another path- strange things can happen.

When strange things are occurring with lights- most of the time it is a grounding issue.

 

[Chris64]

One last question on this topic - the "BRAKE" light in the dash. I was hoping this would be for more than just reporting problems with the proportioning valve, like telling me my parking brake is on. It wasn't working with my parking brake. It does light up when the engine is cranking (I assume that's intended and hopefully not another gremlin). So I started digging around the parking brake looking for a switch of some sort and there wasn't anything there.

So is this light in the dash really only for the reporting proportioning valve failures?

You must be registered for see images attach

 

[legopnuematic]

1973-1977 or 78 the brake light switch is just for the proportioning valve.

My 79 has a switch on the parking brake pedal. My 76 does not. Somewhere between 77 to 79 it was added.

 

[Jgonick]

It does light up when the engine is cranking (I assume that's intended and hopefully not another gremlin)

Yes- it is suppose to- It lights up when it is grounded. When you start the truck it grounds it briefly.
It's a tan/black wire that turns to tan/white or tan in engine compartment going to proportioning valve.

 

[AuroraGirl]

Possibly- It is a dual filament bulb and the side marker (right turn signal) actually grounds by going through the bulb.

I'll try to explain what is possibly happening. As you know, electricity come from the positive side of battery and has to return to the neg side.(conventional) The return path uses grounds (uses the metal of the car) to get back to the battery. electricity is lazy- it will take the easiest path back to the neg battery. So if you have a weak ground-you can think of it like plumbing with a partial clog. A little water everything works fine, however if you add to much water it backs up. Once it backs up it looks for another way back. If it finds another path- strange things can happen.

When strange things are occurring with lights- most of the time it is a grounding issue.

oh i thought he meant it was burnt

 

[75gmck25]

I have a spare instrument panel out of my '75 with gauges and a clock, so I looked at the wiring.

I believe the correct ground is an 18 gauge black wire that comes out of the big multi-plug and runs over to ground on the pedal mechanism. It comes from terminal #150, which is at the far end of the big connector plug and there is a light blue wire right across from it.
Note: There is a 2nd black wire coming out of the plug, but it is on terminal #105 closer to the middle of the large connector, and my diagram shows it is used for the ammeter.

Wiring diagram I have does not even show exactly where that black wire runs to (just has a ground wiring symbol). However, when I pulled an emergency pedal mechanism from the junkyard I found a black wire grounded to it, and when I grounded my truck to the same terminal on the pedal it fixed a lot of the dash lights and instrument issues.

 

[AuroraGirl]

You must be registered for see images attach

I have a spare instrument panel out of my '75 with gauges and a clock, so I looked at the wiring.

I believe the correct ground is an 18 gauge black wire that comes out of the big multi-plug and runs over to ground on the pedal mechanism. It comes from terminal #150, which is at the far end of the big connector plug and there is a light blue wire right across from it.
Note: There is a 2nd black wire coming out of the plug, but it is on terminal #105 closer to the middle of the large connector, and my diagram shows it is used for the ammeter.

Wiring diagram I have does not even show exactly where that black wire runs to (just has a ground wiring symbol). However, when I pulled an emergency pedal mechanism from the junkyard I found a black wire grounded to it, and when I grounded my truck to the same terminal on the pedal it fixed a lot of the dash lights and instrument issues.

 

[75gmck25]

Taylor, I think the picture you posted is of a newer truck than the 74/75 era. For the older trucks I think it was just a single wire connected to that bolt, and in later years they added the bus/fitting for multiple grounds (like in your picture). I only found the missing instrument panel ground wire because I was searching around Pick and Pull trying to find emergency brake parts I could use to fix my truck. It was convenient that fixing my emergency brake also fixed most of my instrument panel issues.

Almost all of the emergency brake mechanism was missing from my truck when I got it, apparently because the cables under the truck caught on something when they were running it through a field on the farm. It pulled out all the cables under the truck and turned the spiral wound cable from the pedal into a corkscrew.

 

[Chris64]

Can you get a picture of the switch on the brake pedal? I could probably wire that right into the existing tan line and make that light be more helpful. Especially since I have driven with the parking brake on.