[jrm123180]

Ok...on my 79 Chevy Truck K10. My brake lights don't work when the park lights are on...also, my rear park lights don't work either, but the license plate lights DO work...The directionals do NOT work when the park lights are on also...but they work together when I shut the lights off (meaning when I put the left on, the right goes on also...and vise versa.)

Any suggestions....I've checked all the fuses...followed the wires all the way back looking for a break or some sort...NOTHING...I'm baffled...could there be a bad switch? could the be something wrong with the fuse box??? Where else should I look??

Hope you can under stand what i"m saying.

And thanks again.
Steve

[Kallie49]

Its more than a fuse, check your flashers (the cans in your fuse block) heck I'd just replace them, also ohm out your brake light switch (I recently had a bad brake light switch that was intermittent, jacked the whole tail up) heck I'd just change that as well ($7.95) Check your headlight switch, if its the one I'm thinking of it would prob do well to replace that as well (I got mine off e-bay NIB for $8 shipping included and the bloke (forgot his user name) still has 4 more. if that doesnt fix it, (which I would be willing to put money on it that it does) start ohm ing wire out and running it back to the fuse block/switches/column....could also be a faulty hazard switch as well (thats a strech though...just something to check) last thing to check (actually the first thing to check) I hav found on some of the chevy rear light sockets over time they get mosture in them and the socket itself wears out....OH check your grounds as well....you got alot more to check besides the fuses...that just signifies you have a dead short somewhere....(for the most part)
I'm sure Doc will step in and give you somemore pointers that I'm not savy enough to throw at ya (I'm no lectrical' guru by any means...just know gentle theory and application)

[docvette]

Doc here,

Check your Tail lamps for the RIGHT bulb installed..in the tail / Brake/ Turn , sockets...If you have the wrong bulb in here everything will malfunction..

If the bulbs are correct you have some issues with the turnsignal switch , and or column plug..or the harness in between..

The brake / Turns are wired through the switch, a bad switch can short them both out..

The tail/parks may be part of a bad harness going up the column or at the bottom plug...

Check those next..I vote for the plug..

Doc

[Bryan59EC]

If you have tilt wheel---the wires from the switch into the column may be broken----I have had this problem 2 times with my 79 c-10.
The last time---only had brake and signal lights with the wheel down.
Switch replacement is probably easier than trying to fix it though.
Bryan

[jrm123180]

Thanks, I'll check the switch....

Think back, this issue started a while ago with the flashers. The flashers would work fine untill I steped on the brake and then they would stop flashing and go solid....and work fine again when I take my foot back off the brake. Could that have been the start of a bad switch?

Thanks again.

[Bryan59EC]

Originally Posted by jrm123180

Thanks, I'll check the switch....

Think back, this issue started a while ago with the flashers. The flashers would work fine untill I steped on the brake and then they would stop flashing and go solid....and work fine again when I take my foot back off the brake. Could that have been the start of a bad switch?

Thanks again.

This is a correct operation--cross off one thought

[docvette]

Doc here,

The Turnsignal AND brake lamps go THROUGH the signal switch..

And operate as thus:

Both brake lamps lit at stop .. no signal selected.

Situation: Stopped, Turning left, left signal selected, :

The Left turnsignal makes connection and flashes, the left brake lamp contact at the signal switch is then OPEN, and shuts off the left brake lamp, so the flasher is isolated from all rears and fronts (except selected side) and it WILL flash, (lamp on, lamp off) If you had both, (even isolated from each other (left and right) you'd never see the signal change intensity..it would be Flash, on, Flash off, brake lamp on and appear as a steady "On"..

The right side is the same.

The switch has the lamp hooked to the center wiper of the switch.

The normally CLOSED side contact will be the brake lamp set of contacts.

The normally open side of the switch will be the signal flasher..

If that switch has filed , or the harness has suffered a meltdown, or the plug / pins at the bottom of the column has gone bad, It can cause all kinds of havoc with the lighting system.

Don't overlook the hazard flasher system also.

Doc

[jrm123180]

Doc does it again.

So I replaced both the light switch and the turn signal switch. nothing. played with the wiring harness at the end of the turn switch harness and the tail lights came on for a sec...as soon as I stepped on the brake blew a fuse and that was it...couldn't get it to come back on after I replaced the fuse. Now I have to uptape all the wires and see if there was a meltdown or figure our where the problem is exactly.

THanks again.
Steve

[Bryan59EC]

If it will help--I have the electrical drawing for that vehicle.
I could scan them and e-mail later this eve. if you would like.
it is really nice to know what color wire does what when working in there.

79 chev service man-----boy has this book paid for itself.

[jrm123180]

Originally Posted by Bryan59EC

If it will help--I have the electrical drawing for that vehicle.
I could scan them and e-mail later this eve. if you would like.
it is really nice to know what color wire does what when working in there.

79 chev service man-----boy has this book paid for itself.

That would be great, i would really appreciate it. Thanks.




Now for an update....everything is still the same....no tail lights, and the directionals don't work properly. When I put on the left turn signal, they both light up and flash, but the right one get brighter...this also happens when I put on the right signal, but the left one gets brighter. I've replaced the light switch, and the turn signal switch...can't find any broken or cracked or melted wires......I'm stumped.

[jrm123180]

It's fixed...it was the simplest of things...which happened to be the first thing that I checked. The problem was the ground at the tail light itself. I moved, and cleaned this ground as the first thing I did; nothing happened. After everything else I had done, I decide I was going to pull the lights out and check them close...decide to check the ground one more time by touching the bumper and everything worked fine.....wish I had done that the first time.

Thanks for eveyones help....as always, its greatly appreciated.

Steve

[docvette]

Doc here,

Donja just hate it when that happens??

Move the ground to a supposed better spot , and it fails...

Yeah, We all assume that everybody checks ground First..because WE do..and tend to overlook it when posting a check list...

Next time you move a ground use a continuity checker from the device to ground to be sure..its good! ALWAYS burnish the area, use a star and lock washer, and be sure the body part actually is on ground. Then Move on..


Thanks for posting back the Fix!
Doc

[sbchevfreak]

but the right one get brighter...

I see you already found the answer, but anytime you see an issue like this, it is almost always a bad ground.