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Username Post: No rear brake lights on 94 Silverado        (Topic#164601)
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-14-07 11:58 AM - Post#1208056    

I am having problems with the rear brake lights on a 94 Silverado. The 3rd brake light works every time. The rear ones work on accasion for like 6-10 times while testing but then quit. Please help

 
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CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
07-14-07 02:09 PM - Post#1208137    
    In response to aerocoupe46

Sounds like a ground but, Use a test light on the switch, or wires of, watch it while pushing the pedal to see if it's intermittent first.

 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-15-07 08:44 AM - Post#1208626    
    In response to CDAUSA

okay I took the brake switch off pedal and wedged the lever , third brake light came on still no rear ones I turned ignition on and rear ones came on switched truck back off brake lights stayed on switched truck back on lights went out. I cut ground wire at rear of truck and cleaned area new connector. traced wires back to front of truck no bad places. I then traced wires from switch removing tape back over to junction box I dont see any thing wrong.

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
07-15-07 09:05 AM - Post#1208641    
    In response to aerocoupe46

I wanted Richard to dive into this one, think he has issues with this. I'm not 100% sure, but I think the headlight switch can be the culprit. I haven't had an issue but if memory serves, it was found to be the problem. Do you know anyone you could borrow one from to try?

 
someotherguy 
Moderator
Posts: 25741
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
07-15-07 09:11 AM - Post#1208644    
    In response to CDAUSA

Hey Steve, the problems I've seen where the brake lights get weird due to something external have been in the 95-up style column. I have yet to tear one apart but I have seen others in here griping about bizarre behavior that they solved by replacing the multifunction switch or the harness to it. But I have yet to see the guts or associated parts of the 94-down interior style cause a brake light problem, so I'm kinda stumped.

I do find it very strange that he gets brake lights, albeit intermittent, once he turns the key on.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
07-15-07 09:21 AM - Post#1208651    
    In response to someotherguy

????? Did this also have something to do with the wiring connector near the dash, and they replaced the multifunction switch to get the connector??

 
someotherguy 
Moderator
Posts: 25741
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
07-15-07 09:39 AM - Post#1208657    
    In response to CDAUSA

I think so.

On the 98 company truck, it was so screwed up that it somehow interfered with the fuel pump wiring (I think there was a minor meltdown somewhere) but when the fuel pump went, I was driving down the road. Pulled it over, and hit my hazards so nobody would run into me - and ALL the lights on the truck flashed. Headlights, cab markers, dash lights, everything. It was a wiring nightmare. And - was intermittent.

Prior to the meltdown, when you'd hit the hazards, the fuel pump would run - even with the key off. Step on the brakes and one of the relays under the dash would sing a horrible buzzing song. That truck was a mess.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
07-15-07 09:56 AM - Post#1208664    
    In response to someotherguy

Too weird

I also had an issue several years ago with this connector, but it was I lost my headlights, not high beams but low. I was so busy during that time I hotwired the lights under the hood with a slip-on connector----did this for 3 days or should say nights til I had time to check it.

This connector has pins the size of the relays, pretty small and just a tension clip on the female side---it takes just so much heat and tension is lost then corrosion takes over. It also would work sometimes in certain positions of the tilt wheel------that was the first clue.

Out here in the boonies, such a thing is not easily accessible, so I just pulled the wires out, made new connectors and repaired/heat shrinked/taped them back-----that has to be over 200K miles ago.

Since other issues come from this, I think I should have pulled them all and fixed permanently.

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
07-15-07 10:04 AM - Post#1208670    
    In response to CDAUSA

Now that we have completely confused and abused aerocoupes thread, let me say this. Somewhere in the past, someone had an issue with brake lights and it was the headlight switch.

But now, we could have an issue with the connector under the cowl of the column?

And I am probably wrong here but maybe not, once fire leaves the brakelight switch, I don't think it goes back to the connector, so I would do this. Take the two wires going to the BL switch and hook them together-----do we have lights or fire to the back? If we don't or it is intermittent, is fire to the switch also intermittent? I didn't say that well, but maybe caught the drift?

 
someotherguy 
Moderator
Posts: 25741
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
07-15-07 10:25 AM - Post#1208676    
    In response to CDAUSA

Where I was going with my first reply is that he has a 94, which has the "old style" pre-airbag steering column, not the cowled version like in the 95-up. I haven't seen anything like this with the old style column. I know that doesn't help much but we should keep his column type in mind if it's going to be a suspect.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-15-07 10:34 AM - Post#1208684    
    In response to aerocoupe46

okay I changed the headlight switch on the dash. I bought a new turn signal switch. I just unplugged the brake light switch and put a fused jumper across the two and the third brake light came on,still no rear. I then switched truck on as almost to engage starter rear brake lights came on switched truck off rear brake lights went out but 3rd stayed on. Checked with test light at switch connector still hot. Also I changed the tail lights out with my 96 Tahoe which worked on it.almost tempted to tie on to third brake light and run new wire to tail lights just to check.

 
someotherguy 
Moderator
Posts: 25741
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
07-15-07 11:01 AM - Post#1208700    
    In response to aerocoupe46

Brake lights should be active on this vehicle (and most) with the key in any position, including off, which is why I'm confused by the behavior.

When you say you replaced the turn signal switch, what part do you mean - the lever that sticks out of the column, or the actual switch/cancelling mechanism inside of the column?

Tying the third brake light into the regular brake lights *may* work to give you "gotta have 'em" brake lights, but you might end up causing more problems for yourself. Do keep in mind the third brake light is on a separate circuit as the turn signals do not interfere with it. I suppose if you took the normal brake & turn signal wires completely out of the picture then tying the circuit in from the third light shouldn't be a problem except maybe in the event of the circuit being undersized for the load, which is a definite possibility. I guess what it comes down to is I'd much rather have brake lights than turn signals, but I wouldn't do this as more than just a very, very temporary work-around.

I'd be very tempted to rule out the brake light switch itself since the third brake light appears to be working normally. I'd never have given the first thought towards the ignition switch (the actual switch is down the column near the brake light switch) because it *shouldn't* be a factor as the brake light circuit is hot at all times, but based on the behavior you've mentioned it could be a suspect.

I've got to run out the door for a few hours but if you can bear with me a little bit - I have the factory manuals for '94 - and can try to scan in some diagrams or troubleshooting charts for you. Autozone's website has diagrams as well, but I'd like to see if the troubleshooting charts in the factory manual might help.

Edit - wait a minute, are you saying the lights from your Tahoe work normally, or they work the same as your original pickup lights do? If the Tahoe lights work normally, then the problem is absolutely gonna be one or both of your taillight circuit boards, though from the way your previous posts read, I wouldn't have suspected them, though I guess it's possible a ground problem with them could play a part in the odd behavior.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


Edited by someotherguy on 07-15-07 11:02 AM. Reason for edit: No reason given.

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
07-15-07 11:09 AM - Post#1208707    
    In response to someotherguy

I would agree with the circuit boards, but somewhere in this I think he said it wasn't gettin fire to the rear----check the plug on the frame where it drops down to the harness---at the very rear.

We've also seen the wires eat up between the tank and the frame.

 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-15-07 11:20 AM - Post#1208713    
    In response to someotherguy

Yes I bought a new switch/cancelling mechanism inside of the column? THe taillights worked perfect in the Tahoe that I took out of the truck so I ruled out the tail lights. I am not in a big hurry to fix it as I just purchased it from my son as he bought an hd1500 crew cab. I just replaced the engine and tranny for him a few months ago and didn't want him to just give it away. I have not even driven it since he gave me the keys on the 4th. I wanted to fix everything else and clean it up before I put it on the road. I sure do appreciate this group for all their help. Jimmy

 
nickmac 
Frequent Contributor
Posts: 1071
nickmac
Loc: Scandia, PA
Reg: 02-13-07
07-15-07 04:00 PM - Post#1208884    
    In response to aerocoupe46

Do you have any trailer wiring hooked into the system? There could be a problem in that area.
Dan
'05 Chevy TrailBlazer 4.2 4x4
'04 Chevy K1500 Silverado 5.3. 4x4


 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-15-07 04:23 PM - Post#1208907    
    In response to nickmac

There was so I unplugged it and connected back as orignal.

 
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
07-17-07 01:33 PM - Post#1210521    
    In response to aerocoupe46

Ok, Im looking at a 97 wiring diagram, I realize your truck is a 94 so take this with a grain of salt.

A 97 has a stoplamp relay in the underhood fuse/relay center, IF that relay is bad or the fuse suppling power to that relay is blown, the brake lights will not work when you step on the pedal. BUT the (cab mount brake light) will still work with that relay being bad.

So check to see if your truck has a stoplamp relay. Check relay and socket for burnt terminals. also
Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon


 
someotherguy 
Moderator
Posts: 25741
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
07-17-07 02:11 PM - Post#1210566    
    In response to 59 EWW

I knew I was forgetting something!!!

Sorry bud; I fully intended to scan those diagrams in but had a really long day and forgot. Here they are now; note there are different diagrams for truck vs. Suburban/SUV so I scanned both in case someone has trouble in the future and searches out this thread.

These are scanned in somewhat large for clarity; if your browser re-sizes pictures automatically they're gonna be hard to read. View them in actual size or print them out for best results.

Scanned from 1994 GM Truck factory service manuals:

Truck
http://www.someotherplace.com/info/stoplamp1.jpg
http://www.someotherplace.com/info/stoplamp2.jpg

Suburban/SUV
http://www.someotherplace.com/info/stoplampsub.jpg

59EWW, from the truck diagram, looks like 94 and 97 are different. I'd venture to say there's a fairly good departure in wiring between the OBD1 and OBD2 trucks in general. The regular brake lights don't appear to use a relay, but the third brake light does.

Sorry for the somewhat crooked scans! Kinda hard to get that thick book settled right on the scanner.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
07-17-07 02:41 PM - Post#1210600    
    In response to someotherguy

Yes, there appears to be some differences, 94 is much more simplified. The relay serves mostly the same function, its just named different.

I dont believe his Turn Hazard Switch is getting power from the Center high mount stoplamp relay.

Check the center mount stoplamp relay and socket.

I believe that relay may be under the plactic cover on the firewall, passenger side.
Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon


 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-22-07 06:43 AM - Post#1213879    
    In response to 59 EWW

Okay still not working properly. I found this morning that the 15 amp fuse in the panel marked BRAKE has very little light on the test light once I put the test light probe onto the source side of the fuse the brake lights work and the test light will light up bright. This sounds like a ground somewhere to me. I have removed all tape from the harness pulled the fuse panel and fuse block at the firewall looked behind it and everything looks to be good.

 
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
07-23-07 02:05 PM - Post#1214863    
    In response to aerocoupe46

Did you find or check the relay shown on the wiring diagrams Richard posted?

According to the diagrams, theres only two grounds related to the rear taillight turn/stop function. The relay has a ground wire which would be black and each taillight is grounded at the rear of the truck also would be black wires or directly ground to the body.

You may want to verify the power flow again.
Starts at brake Fuse,to brake Switch, to stop lamp Relay, to turn/hazard Switch, to rear tailights.
Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon


 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-23-07 06:42 PM - Post#1215046    
    In response to 59 EWW

Thanks CDA USA,Richard and 59EWW they are working perfectly now. A friend came over tonight to help me and he found that when I swapped the transmission I left one of the mainline grounds off the back of the block. Touched the firewall with it and all three brake lights came on. I really feel stupid. But everything is put back a whole lot neater.

 
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
07-23-07 06:48 PM - Post#1215053    
    In response to aerocoupe46

very possible it was the ground for the relay, it should of been in that area.
Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon


 
aerocoupe46 
Member
Posts: 95
aerocoupe46
Age: 51
Loc: Georgia
Reg: 01-07-04
07-23-07 08:51 PM - Post#1215195    
    In response to 59 EWW

Thanks CDAUSA, Someotherguy and 59 EWW.
A friend of mine came over tonight and found the ground that goes to the back of the block not connected from when I swampped the transmission.BOy I feel stupid, but I cleaned up all the wires, taped and straped everything very neat. Thanks again...Jimmy

 
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