no break lights with key in on position

[bowtie_slim]

ive had this 94 2500 4x4 for 6 months now and no problems. out of no where the brake lights quit working while the key is on. the brake lights work with key off but the display for heat and air lights up with pedal down and the defroster door moves back and forth. also the break relay was clicking when pedal pushed. yesterday i bought the relay replaced it and the relay stopped clicking. replaced the brake switch and still the same thing. on another note im beginning to think its a ground problem somewhere. last night going to the gas station my headlights were flickering like crazy. im lost and i would appreciate any kind of suggestion as to where to start.


thank you in advance.

[ChevLoRay]

to our forum....now your forum, too.

My first guess is that you may have a grounding issue, but that doesn't mean it is the answer. Seems like the brake light circuit may go through the turn signal switch. Flickering headlights could be a circuit breaker (for the headlights) that is going bad, but that's just a guess without any merit. The brake lights working/not working may be the circuit board that the bulbs are in, in the taillight housings. I'd also check the grounds under the hood that are related to the headlights. Look on the radiator support ass'y.

You guys do get some snow up there in KS, and I suppose that salt gets used on the roads. Since you have a 4WD, do you do any plowing? If so, that could have increased the chances you got some issues with grounding and the condition of the connectors on the wires and where they are used to ground a circuit.

[Xuare]

^^^

They could also be dependent on hazards, as well. Generally, the brake lights are not dependent on the ignition switch, so I would rule it out as a direct cause.

You may want to monitor your voltage as well. When you say the key is on, does that me the truck is running, or the key is on but the truck hasn't been started yet? Could be something tied to the ignition switch is sucking a lot of current and dropping the voltage? If you have a diesel, glow plugs could do that, as would a few other shorted electrical items for all truck types...

[bowtie_slim]

I appreciate the replies and i guess im gonna have to get a meter out and get to work. I bought the truck in richmond missourri and man did it have some rust. The frame was cracked at the rear wheel wells and i thought it could be fixed. Wrong answer. I had to buy another frame and do a complete swap and redo the whole suspension. When i put it back together it went smooth and everything worked fine. Then one day going down broadway some college chick went off on me saying get my tail lights fixed. It just stopped working.

On another note thank you for the replies.

[ChevyTech]

It sure sounds like ground issues.

When you but the truck back together did you:
Put a ground wire from the box to the frame?
Put a ground wire from the cab to the frame?
Put a ground wire from the cab to the engine?
Put a ground wire from the fender to the negative battery connection?

[bowtie_slim]

Its all there just as i took it off but some of the grounds pretty crappy.
Im just gonna put new grounds altogether and then go from there.

thanx for the input

[bowtie_slim]

okay tore everything apart put all new ground wires. tested all and still backfeeding but not through the ground wires. could this be the turn signal cam switch or light switch?
what about the ignition module on the lower part of the column. the lights had a ground wire not connected and still have flickering headlights. took the grill out and checked for pinched wires and that sort. im at a loss for explanation on what to do. its been a really good truck other than this wiring crap.

thanx for the help guys. ill keep trying!

[ChevyTech]

The earlier trucks of this body style had a common failure of the circuit board in the tail light assembly, and the ground circuit was the problem circuit.

You need to take a test light a meter and test for voltage on the ground side of anything that does not work correctly. Thing is you should be using a known good ground to connect the test light/meter to which means starting at the battery testing the fender, engine, frame, for voltage on the ground or using a long lead to connect you test light/meter to the negative battery while you are probing the tail light circuit boards.

Test for power at the brake lights while you have them open and the test equipment in hand.

Negative battery cables do go bad too so just looking at everything may not find the problem. Test for voltage on the ground side of equipment.

[bowtie_slim]

okay this may sound stupid but i need to retap the bed bolt holes to bolt the bed all the way down. its just kinda setting there. could this be my problem?

[ChevyTech]

Originally Posted by bowtie_slim

okay this may sound stupid but i need to retap the bed bolt holes to bolt the bed all the way down. its just kinda setting there. could this be my problem?

Yes that could be a problem!

Before you lifted off the box did you disconnect the black ground wire that goes to the frame in the driver’s side rear corner? Did you connect back up yet? Did you just leave it connected and ripped the wire off?

Electricity is not only flowing to the tail lights and getting consumed and goes to nowhere.

Electricity needs a path back to the battery to make the lights work.

If the box is just sitting on the frame with the grounds disconnected that needs to be corrected.