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Discussion Starter #1
Hey gang,

This isn't a question pertaining to my Chevelle, but rather my 86 Silverado. But anyone with electrical knowledge could help me with a starting point. My brake lights are shorting out and blowing the fuse and I have no idea where to start looking. The running lights and signal lights all work fine... the only things on this fuse that I am aware of is Hazards and Stop lights - should I start at the taillights and work my way forward, or is the short likely somewhere else? Any help would be greatly appreciated.
 

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If the turn signals work fine it would not likely be in the light assemblies themselves. I would first look at the break light switch at the pedal and then I'd look at the 3rd brake light and work forward. The third brake light is the only light that comes on ONLY when the brake lights come on. Another test would be to turn on the hazards which I believe does not activate the 3rd light. If this does not blow the fuse the problem would have to be in the 3rd light or 3rd light circuit or the brake light circuit somewhere.

*EDIT* Oh heck! Did trucks even have the 3rd brake light in 1986? They became mandetory for cars that year I recall, but I'm not sure about trucks. Duh.

[This message has been edited by Rich-L79 (edited 01-24-2002).]
 

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If you have changed, modified, or tampered with anything near the wiring (like body work near this harness, adding gauges etc) - go there first and look.
If you have done nothing, start with the light assemblies and wiring near them.
Then under the dash near the brake light switch - the switch could be bad.
Other than that, start tracing the wires- - - ugh - good luck


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Discussion Starter #4
Thanks a lot guys. If it's not the switch by the pedal then I'm in for a long search I fear. I'll let you know how I fair. Unfortunately it's -30 here right now, too, and my garage is taken up by my Chevelle!
 

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You can eliminate all the rear lamps and rear cross harness's and connections by unpluging the main flat wire connector coming from the front. The wiring runs along the inside of the left frame rail. This connector is easy to see under truck( at left rear). If the trouble dissapears when unpluged I would look to see if the wiring was cut,spliced and taped for a trailer connector. Common source of problems.


Rene


[This message has been edited by shooter (edited 01-24-2002).]
 

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shooter has a good idea if you unplug the harness and still blow fuses thenit is farther forward, if it doesn't chevrolet trucks were notorious for the light strip to go bad this is in the back of the light assy. has one big plug and unscrews from the housing and exposes all the bulbs in one strip. any chevrolet dealer will have that strip in stock it was not one of their bright spots on design. hope this helps.JIMK
 

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as far as I know the dash lights are on the same circuit as the tail lights.......so no tail lights no dash lights.......so you may also want to look there.......
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by malibu350:
as far as I know the dash lights are on the same circuit as the tail lights.......so no tail lights no dash lights.......so you may also want to look there.......<HR></BLOCKQUOTE>

Tail Lights and brake lights are two different circuits


HI ROLR Does the fuse blow instantly or intermittently ?
 

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Discussion Starter #9
The fuse does not blow instantly. After 6 hours I have still not solved this mystery. I replaced the stop light switch, checked all the wiring under the truck to the sockets, checked the sockets - everything seems fine! The fuse only seems to blow when I'm in reverse! I drove all the way home from the mall and the fuse didn't blow until I backed into my driveway.

The reverse lights are on a completely separate circuit as I thought maybe when I shift into reverse it blows the fuse - this seems to be the one consistent way to get the fuse to blow. Otherwise I can run the truck all day while it's in park, hitting the brakes all I want and the fuse won't blow. I am completely 100 per cent stumped so I'm taking it in to have the so-called professionals look at it. I give up! But thanks to everyone here for their suggestions and help. I'll let you know what the pros say.
 

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I don't have a schematic on that truck but I'll toss the out anyway. On some cars they wired additional items into the neutral safety switch. One thing is the reverse lights and another was the seat belt warning system. The seat belt warning system brings ground lines into the switch. One guy last year had an intermittent fuse popping problem. After a long search, found an intermittent problem with his combination neutral safety switch shorting lines to ground.
 

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Discussion Starter #11
Well gang,

I've officially been violated. 240 bucks to replace the signal light switch. Can you believe that? No wonder I couldn't find the short. It never occurred to me that the wiring in the steering column could cause the brake light/hazards fuse to blow. Oh well. No need to worry, Visa's paying for it.

(This is the only way I know how to vent right now without braking (get it?) something.)

ARGH.
 

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Actually I think the price is in line with the better shops around here. They took some time diagnosing the problem and changed the switch out. Some of that was the switch price? Intermittent problems are the worst to work on. Doesn't matter if the car is new or old. With a intermittent problem, it's great they found it right away.
 

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Discussion Starter #14
John,

Your words are encouraging. That is in Canadian dollars as well and yes it includes the part and 13 per cent sales tax. The scary thing is, they used the process of elimination to determine this was the problem. If they overlooked something and are replacing the switch unnecessarily, I'll be quite upset... I'll also be out 240 bucks. But we'll see. I pick up the truck in 2 hours.
 
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