Vehicle: 1986 Brat GL Weber Carb swap, D/R 4spd

 

My dash indicator "brake dummy light" started rearing it's ugly head a while ago, in addition to the turn signal right arrow blinking as if the lamp was out

First thing i did was swap the bulbs out in the passenger side assembly, as this was where things were funky.

No change.

Cleaned the ground that is behind the bed access panel.

No dice.

 

The major problem is that the entire tail light assembly goes dark when applying the brake pedal, rather than illuminating brighter.

 

The fuel gauge has always been unreliable, but it stopped working completely after cleaning the ground wire.

 

Which may be a clue to someone as to the circuit in question.

 

Last night I checked the lamp connectors for corrosion, cleaned them, as well as inspected the wiring/pigtails for damage.

This got rid of the rapid turn signal indicator, for now...

 

I am kind of stumped as to what is going on here, and i dont feel like being pulled over for something so idiotic.

HELP! S.O.S.

 

Thanks in advance

Edited September 16, 201312 yr by Greenley

sounds like a pinched wire  short somewhere in wiring harness in rear of vehicle (particularly in  braking circuit which could also be causing the other problems)  so suggest checking all wiring from cab rearward.

know this is irrelevant in this case but had a similar situation with another  car and found the rear seat was pinching wires.

Edited September 16, 201312 yr by subnz

I think you have a grounding problem. Clean the battery to chassis ground and the ground for the taillights. You could also try running a temporary ground to the rear light to see if that proves a bad ground connection.

I think grounding problem. Clean the battery to chassis ground and the ground for the taillights.

 

Thanks Cougar, I have cleaned every ground in the engine bay,

in addition to running a 4 gauge ground from engine to chassis.

I believe the tail light ground wire to be the black wire behind the passenger side bed access panel. When I cleaned it up and reinstalled, that is when the fuel gauge went dead.

 

When you say run a ground wire to the affected lamp socket,

do you mean splicing into the existing one into a known ground?

 

What role does the pedal play in the circuit?

I ask, because just a minute ago, with the ignition turned to ACC, depressing the brake pedal was actuating the headlights (*confused*) and then it stopped.

Edited September 17, 201312 yr by Greenley

sounds like a pinched wire short somewhere in wiring harness in rear of vehicle (particularly in braking circuit which could also be causing the other problems) so suggest checking all wiring from cab rearward.

know this is irrelevant in this case but had a similar situation with another car and found the rear seat was pinching wires.

I'll look into a short, or pinched ground

broken ground wire was the issue here.

 

The fuel gauge is still not responding.

The trouble you had with the brake lights and head lights pointed to a bad chassis ground connection as the trouble. Good job! The brake light switch is tied to power that passes it on to the brake lights and then to ground to turn on the lights when the pedal is depressed. If the grounding for those lights has a problem the circuit will seek any connection to ground it can find, which was through the head lights somehow.

 

The fuel sensor problem may be due to another faulty ground connection to it, so add a temporary connection to ground to the sensor ground and see if that changes things. If that doesn't make a difference then the power connection from the gauge to the sensor needs to be checked.

Sending unit for the fuel gage is on the rear of the tank, electrical connectors are there also. Check the connections for corrosion. Been the cause of my gage issues on all 5 of the BRATs I have owned.

Thank you for the help Cougar, you're always on point when it comes to electrical diagnosis!

 

Tom, you know the bullet connectors were incredibly corroded, they broke upon disconnection.

I ended up cutting out the bullet connectors and splicing them together.

Still no fuel gauge function.

 

I cant tell which wire is ground due to lack of access to a DVM or even a test light, (will search for that info)

So i think i'll try what Cougar suggested, and hard ground the sensor.

Even a low fuel light would be sufficient, as tracking mileage is pretty easy, but not always accurate with this brat.

Power for gage and Low Fuel Light is from fuse 12 on a Black/White wire.

 

At the sending unit, low fuel is White/Yellow wire, Gage is Black/Yellow.

 

Both gage and low fuel light are grounded thru the tank/body of vehicle.

It sounds like it is time to purchase a meter.