Brake + Turn Signals = Not Working

[litew8]

Anyone got some insight on this type of trouble?

Rear:
Tail lights = Yes
Marker lights = Yes
Brake lights = No
Turn signal = No

Front of cab is working ok.
No power to two of the three wires at the rear connector. Does this sound like a bad brake switch or turn signal switch? Not sure if the rear turn signals go through the brake switch or not. Any help greatly appreciated. We don't think it is a ground issue since there doesn't seem to be power at the plug for two.

[Blakeman350]

The brake lights sounds like a bad brake switch and the turn signals could be the switch in the column or maybe just a bad relay. Electrical problems suck I'm going through some myself. Good luck.

[litew8]

Thanks man I think we switched blinker relays around but the rears still wouldn't work. Would that indicate more of the switch in the column? From what I've read, both go through the switch in the column. The trouble started just before the restoration so I know it isn't something we did.

[Blakeman350]

Ya I would try changing the switch in the column. Sounds to me like that's the problem.

[TheOtherScott]

Have you had your steering wheel off lately?

Silly as it sounds mine kept blowing fuses for the tail/brake lights because I pinched/shorted a wire when re-installing the turn signal assemble under the steering wheel. My wife thought I was nuts; I had been studying the schematics and said "son of a b*&%#", went to the garage and came back in 15 minutes and told her I had fixed my problem. My $.02 worth, won't hurt to check it out...

[litew8]

Haven't taken the steering wheel off. I do need a new one though. The last time they worked was just before I got pulled out of a muddy service road in the rain.

[Heavymetl]

Everything grounded properly?

These days with any electrical problem I have the first thing I check are grounds.

[litew8]

Thanks for the feedback everyone.

Heavymetl, mostly all properly grounded. There are a couple areas I'll be addressing. But we're thinking it isn't a ground issue since there's no juice hitting 2 of the 3 wires on the connector (rear/frame) for the harness. If we followed those wires back to the cab, would they lead to the turn switch in the column before anything else?

[cdowns]

mostly all properly grounded?? what the heck does that mean?? they are grounded or they are not grounded?

[VetteVet]

It's pretty easy to check the power through the turn signal switch.
Check for 12 volts on the white wire from the brake light switch with the prdal depressed.
If it checks for 12 volts then check for 12 volts on the green and yelllow wires in the steering column harness with the brake pedal depressed.
If that checks the the power break is in the harness to the rear of the truck.

To check the turn signals- check for power on the purple wire in the steering column harness with the key on. If you get 12 volts,
Turn the switch lever to left turn and check for 12 volts on the yellow wire in the harness.
If you get 12 volts then turn the switch lever to right turn and check for 12 volts on the dark green wire in the harness. If you get it there too then your problem is between the cab connector and the rear of the truck in the harness or the connectors. If you don't get 12 volts on these wires then the problem is in the turn signal switch.

[litew8]

Originally Posted by cdowns

mostly all properly grounded?? what the heck does that mean?? they are grounded or they are not grounded?

There's an old busted ground strap at the driver side rear of the frame rail that isn't attached. I'm not sure it is stock or what, since I've read about people grounding the frame to the bed manually (implying it was never factory). There might be another one up under near the cab. Otherwise, grounding is good in the other areas. If it were a grounding (bed to frame) issue, I'd think the rear marker lights and rear tail lights wouldn't light (like the are) when the headlights are engaged. Besides, like mentioned a couple times now - we tested the plug in the rear frame for power. Only one of the three wires were live. The one that was live is for the tail lights/marker lights I'd guess, since they are working. Implying that the loss of power is coming from between the plug and the cab.

Originally Posted by VetteVet

It's pretty easy to check the power through the turn signal switch.
Check for 12 volts on the white wire from the brake light switch with the prdal depressed.
If it checks for 12 volts then check for 12 volts on the green and yelllow wires in the steering column harness with the brake pedal depressed.
If that checks the the power break is in the harness to the rear of the truck.

To check the turn signals- check for power on the purple wire in the steering column harness with the key on. If you get 12 volts,
Turn the switch lever to left turn and check for 12 volts on the yellow wire in the harness.
If you get 12 volts then turn the switch lever to right turn and check for 12 volts on the dark green wire in the harness. If you get it there too then your problem is between the cab connector and the rear of the truck in the harness or the connectors. If you don't get 12 volts on these wires then the problem is in the turn signal switch.

Thank you VetteVet for the breakdown, much appreciated!

[leddzepp]

Is the turn signal harness plugged all the way in?

[litew8]

From under the dash? Haven't gotten that far yet.

[leddzepp]

Yes, check the horseshoe connector and make sure it's plugged in all the way. I had a turn signal problem that drove me nuts, front signals worked but the rears did not. Turned out the connector was plugged in at a slight angle and not seated all the way.

[chiefcfd]

Check the wire from the firewall to the rear connector. I had one that came in contact with the exhaust and burned it into. It can be any of these things.

[litew8]

Thanks everyone for the feedback! Monday, we'll check the firewall then the connector under the dash first. If that doesn't provide any positive results, we'll test for power at the switch.

[litew8]

Checked the horseshoe connector and firewall. Horseshoe secured OK. Tested the wires per VetteVet instructions. Brake switch tested GOOD. Turn wires are reading funny. Jumps around inconsistently from 3-10 and never hitting 12. Rechecked the plug at the rear and it is jumping/reading the same. Key must not have been turned when we tested the other day which would explain why they appeared dead. Getting the flaky readings for the turn signals, but either way - the brake/turn lights at the rear aren't lighting even a little. My first guess would be corrosion in the turn switch causing the fluctuating readings.

The other strange thing - when the turn signals engage, it causes my tach to jump in sync with it. I noticed also, my tach will jump around when shifting gears (park to reverse to drive to park etc..). Some of this may end up being ground related, but I don't think it all is. Looked at the one ground strap under pass. side cab. It is on, but I don't think I ever removed it to clean it up when we worked on it. Probably the one thing that never got touched . Bought a couple more straps and will add one to the rear to replace the busted one.

So we are kind of stumped. My guess would be corrosion for the turn switch. Haven't removed it to check. Thoughts?

[VetteVet]

Separate the steering column harness.
Check for 12 volts with the key on on the purple and brown wires.
check for 12 volts on the white wire from brake switch with pedal pushed,
If you get the volts then jump from the white wire to the dk green and the yellow wires.
look for the brake lights to come on. Key on.

Jump from the purple wire to the yellow and light blue wires and look for the left turn signals to blink.
Jump from the purple to the dark blue and dark green wires and look for the right signals to work. Key on.

Jump from the brown wire to the four wires above and look for the hazards to come on and blink.

If you get these to work then you have bypassed the turn signal switch and it is the problem.

[litew8]

Thank you again, VetteVet. We haven't had time to check but when we do I'll report the findings here.