I just got this car and can't figure out why the 3rd brakelight (humpback style) isn't working:
Here are a few details:
- checked fuses ... all ok
- rear window defoger goes on
- bulbs are all OK

I don't understand how GM designed this brakelight system to work along side the defoger system.
I'm hoping this is something simple because I need to get this car saftied so I can drive it!

Any ideas anyone?

Pacer

 

Have you checked the brake light switch on the brake pedal. It has two circuits inside it that operate independently of each other. One is for the regular brake lights and the second one is for the third brake light. Also another board member who was having a similar problem found his problem was dirty contact. Have you checked all the wiring for the light?

 

Thx Trickster,

I will check the contacts again, they appeared very clean yesterday, but I never wiped them down.

I also think I may have had the hatch sitting ajar when applying the brake. I suppose this may be it, you think?

Anyways, i will have the car home next weekend so I can pursue this further. Hope I can pick your brain if I still have a problem.

Pacer

 

Yes, if the hatch is ajar the brake light won't work. And sure, you can pick my brain for stuff.

 

Trickster,

You mention there are two contacts on the brake pedal which operate independantly. I assume the same would be true for all third brake lights, to include the one housed in the spoiler?

JamesC

 

No, what I mentioned is that there are two circuits inside the brake switch on the brake pedal that operate independently of each other. One is for the regular brake lights and the other one is for the third brake light. If one circuit in there fails, the other one will continue to operate. Here are the schematics for it. And yes this would also apply to the one in the spoiler.

 

page 2

 

page 3

 

Here is a similar problem to his brake light one. When I first got my 86 Firebird the third brake light was all burnt out, its the third eye style as compared to the spoiler style. A while later I replaced all the bulbs and my brake lights stopped working. The third brake light still worked, but the tail lights didn't get any brighter.

So the other day I was putting in new tail light assemblies and I decided I was gonna try and figure it all out. So me and my buddy checked the fuses and then replaced the burnt out one. Still didn't work. So we thought maybe the third brake light was shorting it out. So we took all the bulbs out of that and viola, it worked again.

Well, kind of. Know the tail lights turn on, including all the dash lights and all that. And there is no noticeable difference in the brightness of the tail lights when the lights are on.

If you guys have any ideas on how to fix this, I'd appreciate it.

 

Did you replace the tail lights for the brakes with the correct dual element bulbs? Also which model is your firebird? Is it the standard firebird, firebird se, or the trans-am?

 

I believe I replaced them with the right bulbs, There were a bunch of bulbs and these were the only ones that fit.

And she is your basic 86 Firebird.

Thanks.

 

On the spoiler brake light option. Could I simply tap the brake light wiring near the hatch or would that cause some sort of electrical problems, like too much draw?

JamesC

 

To James C., It would cause a problem. Is that the original spoiler or did you add that on later?
To Jaded: Check your bulbs, there are a lot of bulbs that look like they will fit and do fit. However it takes a #2057 bulb for the tail/stop & directional socket on your car.

 

Trickster,

My 85, of course, doesn't come with the third brake light, but I've always liked the idea of the spoiler light. To make this work, I'd have to use the appropriate brake switch and wire to the hatch connection?

JamesC

 

You could add the wiring in for the third brake and change the brake light switch on the brake pedal. I will e-mail you a diagram showing the wire routing it tonight.

 

Cool. I appreciate your help.

JamesC

 

I'll check out those bulbs, thanks.

 

Trickster,

I found this old post:

https://www.thirdgen.org/techbb2/sho...hreadid=241873

It appears that all I need is the appropriate brake switch, wire to the rear contact, and I'm good to go. That pretty much it?

JamesC

 

That is the information that I was going to send you. Make sure that you get the piece that goes in the rear trim piece and run the wire through connector C206 and I believe that the ground wire back there goes to the frame. The only wire going there from the brake switch is a yellow wire and it runs down the left side of the car under the door sill in that track there.

 

Trickster,

Can you describe these a little more?
Need to know what I'm looking for.
It rained this weekend after i picked up the car so hopefully this week I can get at it.
Btw, I locked the hatch firmly and still no light.

Pacer

 

I will try to explain it a little better. If you have the correct brake light switch on the brake pedal, there will be three wires going to it. If you will look at the schematic I posted you will see them. There is an orange wire going to the "STOP/HAZ" fuse on the fuse panel. There is a light blue wire going to the regular brake lights and then there is a yellow wire going to the "THIRD" brake light that is either in the spoiler or mounted on the hatch glass. Also check to make sure that plate in the trim at the back of the hatch area is clean and has the wire harness connected to it. That is where the third brake light gets its power when the hatch is closed. If you need a picture of it let me know and I will post it Better yet, go to this link and you will see a picture of it that I posted some time ago.

https://www.thirdgen.org/techbb2/sho...hreadid=241873

 

Trickster:
Couple of things from my 86 glass mounted stoplight:

1) I cleaned the contact plate & contacts. No change.
2) Before I read your response, I removed the 2 screws from the contact plate and removed it from the trim panel. I didn’t notice any wire harness attached to it as you suggested above. I thought this kind of strange. Could this be it? The defogger seems to work. Does the current just pass thru the contact plate? Or am I missing a harness that fell off? I don’t believe this car was ever touched before and I didn’t see a harness lying below … unless I missed it? Diagram 10-7-3 (Body Rear End) does not show a harness attached to the contact plate.
3) My test light indicates that power runs between the 2 connections along the window where the shocks are. This is good news but I don’t know where to go with this further. Reading schematics is my weakness.
4) Fuse C206, LH front of luggage compartment from the diagram you provided: in your estimation (before I take seats & things apart) how likely is that fuse to be the culprit?
5) Haven’t checked the brake pedal wires yet though.


Hope you can shed more light … been a great help thus far.

Pacer

PS, Car’s going into the shop tomorrow so I won’t tackle any more for a week.

 

3rd Brake light in the spoiler on my 90.Doesnot work.Just reinstalled it.Because previous owner took it off and put on a thinner spoiler.Didn't like thinner one or the differance in paint around the area so picked one up at the bone yard.Worked for three seconds then craped out.Tested wires and strip for bulbs.They light up test light/lights fine so workin mechanicaly.Bulbs however are all burnt.When it lit up the first few times some were out already so not a stretch to have the last to do same thing.However I can not find anything other than halogen bulbs to replace them with.And have tried halogen bulbs in side marker/turn signals b4 and know they tend to melt the fixtures after time.
Does anyone have the PN for these bulbs or a source to get them from?If not I'll end up modifying the fixture and use LED's.They burn brite but cool so not worried about meltdone.

 

Bill. the part number that will work in your third brake light is #906 and can be found at any auto parts store or wally world. If you do a search, there is also a suitable sub that can be found at radio shack. There is also another part number that is about $9.00's each. If I remember correctly the p/n is 812 or something like that.

 

The 906's are the halogen bulbs aren't they??Those bruned the same style sockett in the other 3rd eye spoiler i had.The only ones with the pin style i've found are halogen.Due to that meltdown kinda leary of tryin them especialy at 6.99 a piece for 5 bulbs.Autozone price.Awww heck i've been wantin ta try LED's anyways.

 

No, the 906 bulbs are not the halogen bulbs and will not melt the lens.

 

OK I'll tripple check in the am on da way home from work.Thnx...Bil

 

Nope theyre not halogen.But not the right bulbs either.Those 906's are like the 194 , but pregnant lookin.Wrong blade style and too thick.The 1's in my spoiler ,and theres 5 of them, look alot like the 194's or what is commonly used for the light in the shifter or the bigger lights in the gage display.But they are narrower and have 2 little posts about as thick as the conductor in a 12 gage wire.The posts or legs are stiff and stick straight down.Like if ya took a 194 and pulled the wires that are up either side of the glass base where ya plug em into the socket and bent them straight down,then added some solder to those same contacts and made them solid.Also slightly more narrow and the round bulb section is slightly shorter.
The closest ones in style and look are the mini hallogen bulbs that all the advance/zones sell.
Totally bummed.Guess i'll have ta either hit the yards and pray or go LED.The 906's are type used in the high 3rd eye light.Not the 1's for the 3rd eye in the spoiler. even autozones PC said they didn't stock them.(I asked this time)
Thanx anyways.Anyone else??All my searchs turn up squat.

 

I work at advance and brought them up on our computer at work. The correct part number is #891 and yes they are halogen bulbs. I had mentioned a 800 number in one of my earlier posts but had the number wrong. The #891 bulb is what I have in the third brake light on my 89 Iroc. I bought them from auto zone several years ago and they cost me over $9.00 apiece. Nowadays they have them at advance for $6.99 each. Yes they have the two wires sticking straight down like two legs.

 

Ok I'll try those but same spoiler as last time same bulb .Lasttime it melted the socket.The replacement halogen has a point at the top the stocks don't.I ended up trackin them down b4 but forget where.
I don remember if A/Z carrys the LED's I was considerin.But advance does for basicaly 9.00 for 4 LED's on individual wires.12 volt install.RED BLUE and WHITE.Strongly considerin those and fabing a holder for each socket.They are brite and burn cool.Just dunno about how brt in the daytime.That way if the 891's burn the sockets like the last halogen did can at least salvage the eye assembly .
Thanx trickster.

 

Dang yesterday was lucky at the salvage yard.Trickster ya were right bro.They dropped a 89 R/S with same spoiler brake light about 10 minits after i hit the lot.Popped it out hit it with my cordless drills 14.sumthin batt and 3 of the 5 bulbs lit up.Bought that puppy and finally got it open.(lill screws were rusted till no philips would remove)It had 2 round bulbs like my factory ones.And 3(ones that worked)with points just like the 1's that are halogen.So since this one had a hole in the lens went ahead and threw it on the spare car batt for about 45 min.Didn't melt down like hte other one did.I did notice that these don't have a black cap painted ontop.Could that be the diff??The ones i used,dug it out the scrap box in the shed/workshop and chipped it open,had some kind of black cap painted ontop the bulb.
Oh well either way,Trickster ya were correct.Thank you.And I now have a spare lens setup and 21.00 worth of bulbs for 3.00.

 

I put LEDS in my 3rd light from:
http://www.custom-leds.com/

I think around $5.00 + shipping.