I'm working on an 85 GT and have an issue with the dash brake light. I've checked the forum archives and seem to have the opposite problem as many of the others. My light doesn't come ON with the brake engaged.
When I bought the car, it was missing the infamous "blue dingy thingy". I've since replaced it and figured out why it was removed. The thing continuously chimed. Like others in the archives, I traced this back to the parking brake switch being bad. The switch was broken and constantly shorted to ground, regardless of the brake being engaged or not. So, I've fixed the switch so now the "blue dingy thingy" only chimes when the brake is engaged... as it should. However, the light on the dash does NOT illuminate like it should. My first thought was bad bulb/socket. So, I shorted the switch in the proportion valve (near the brake master cylinder) to see if I could make the bulb come on this way, and it DOES. So, I've got a problem somewhere and don't know where to look. Is there something wrong with the "blue dingy thingy" or something in the wiring to the bulb? Any information is greatly appreciated. Perhaps a schematic of the dash brake light.
Does the light go on when you push the brake pedal? I don't have that schematic, but I can't imagine why a switch at the proportion valve would light up an e-brake warning light, unless perhaps you have a connector backwards at the blue dingy thingy.
GALL, thanks for the quick reply! I can tell you while driving the car last year, the light did NOT come on when pressing the brake. It is currently up on blocks and not drivable while being worked on. I'll have to check it this weekend and get back to you.
As for the proportioning valve, it was my understanding it OR the parking brake switch would illuminate the light on the dash. If I'm wrong and the dash light is ONLY for problems with fluid pressure, then I guess I don't have a problem. Can anyone else comment on inputs for the dash brake light?
I'm confused. Are you saying the dash light doesn't come on when you push the brake pedal? It isn't supposed to. If the light comes on when you push the brake pedal, it means something is wrong with your brakes! It's only supposed to light up when you apply the parking brake, or if there's a pressure imbalance in the combo valve.
[This message has been edited by Blacktree (edited 02-24-2014).]
Boostdreamer, currently my parking brake cable is disconnected at the back passenger wheel because I had to replace the velocity boot. Any idea on how the cable's tension would affect the light coming on? I'll try connecting it all back up this weekend and see if that helps. Thanks for the input.
Blacktree, my apologies for not explaining very well. No, I understand the light is NOT supposed to come on with the brake pedal. My issue is with the PARKING brake. I fixed the switch at the base of the parking brake so it works correctly but the light still does not come on. The "blue dingy thingy" chimes while the parking brake is engaged but the dash light does not come on and I don't know why. As I tried to explain earlier, I verified the bulb is good because it WILL come on if I short the pins together on the combo valve switch, simulating the pressure imbalance you mentioned. Sorry for the confusion.
OK, gotcha. In that case, it sounds like you have a wiring fault. The dash lamp obviously works. And the parking brake switch works, because it activates the chime. You can also rule out the connections at the parking brake switch and the instrument panel... and of course the fuse.
If it were me, I'd be tempted to run a jumper wire from the chime to the instrument panel, and see what happens. If the brake light suddenly starts working again, then you know for sure there's a break in the circuit somewhere.
Ok, awesome. A broken wire is easy to fix... once you find it.
Is there a wire that goes from the chime unit to the bulb on the dash or is there a "Y" connection somewhere between the parking brake switch and the chime where one branch goes to the chime and the other to the dash bulb? I wasn't sure if there was a dedicated wire from the chime unit because the pinout I found for it didn't mention anything about an OUTPUT to the light on the dash. It only mentioned an INPUT from the parking brake switch. (Here is the pinout info I found for chime unit courtesy of The Ogre's Fiero Cave and Fiero Tech Zone.)
Hopefully this sketch helps to illustrate my question.
Thanks for the info!
[This message has been edited by 85_redbird (edited 02-24-2014).]
I don't remember for sure, but I think the wire splits off to the chime and gauge panel. I suggested a jumper from the chime to the gauge panel because you could use a shorter wire. But a jumper from the parking brake to the gauge pod should work the same.
Blooze, THANKS! That's the schematic I've been looking for! I didn't realize there was an inline diode. It's likely the problem. I'll trace the purple wire off the parking brake switch back toward the dash until I find it... unless you have an idea where it's located?
I wouldn't be surprised if it has just been cut out to keep the light from turning on altogether. (Like I said before, the parking brake switch was broke and was always a closed circuit.)
Here's the image from the FSM regarding where the diode is... it's also accompanied by the following cryptic description of the location: "Behind instrument panel near LH shroud"
(Edit to add: C200 is the large through-wall connector behind the fuse panel)
[This message has been edited by Bloozberry (edited 02-25-2014).]
Blooz, I gotta say thanks again!!! I worked on the car Saturday and confirmed it was the diode that was bad. I'll refrain from repeating the colorful language I used trying to find and get to it but once I did and replaced it, both the dash brake light AND chime worked as intended.
I'd give you a +1 but I'm still too new of a member to give user ratings.
My light doesn't come ON with the brake engaged.
