No brake lights on the 80 model
06-28-2008, 10:00 PM
#1
Drifting
Thread Starter
No brake lights on the 80 model
I've done a search of the archives and THINK the problem may be the 2 pressure switches. Most threads either replace or clean them.
First the problem.
No brake lights.
All other lights work.
Cruise works...which shares fuse with brake lights.
Brake light warning in dash ON.
Check fuse...OKAY.
Check stop light BULBS...OKAY.
If the pressure switches are the problem...how do you remove...or even what do they look like? I THINK I found them but am not sure and the MSM doesn't say a thing about them that I can find.
Any help would be appresiated....before I get rear ended!
First the problem.
No brake lights.
All other lights work.
Cruise works...which shares fuse with brake lights.
Brake light warning in dash ON.
Check fuse...OKAY.
Check stop light BULBS...OKAY.
If the pressure switches are the problem...how do you remove...or even what do they look like? I THINK I found them but am not sure and the MSM doesn't say a thing about them that I can find.
Any help would be appresiated....before I get rear ended!
06-29-2008, 01:11 AM
#4
Rennlist Member
Have you first identified, from the diagrams, which lead on the CE panel represents the brake light power? ( If you have power there during brake pedal depression, its not the switches, but very possibly the bulb comparator.)
If the bulb comparator unit has failed in a certain manner it will, itself, interrupt power flow to the back of the car. A bit ironic for a device that's supposed to monitor the lights and prevent getting the car rear-ended.
Based on a quick overview of 80 diagrams, I think the brake light circuit should show power at S6 with pedal depressed. (confirm)
If the bulb comparator unit has failed in a certain manner it will, itself, interrupt power flow to the back of the car. A bit ironic for a device that's supposed to monitor the lights and prevent getting the car rear-ended.
Based on a quick overview of 80 diagrams, I think the brake light circuit should show power at S6 with pedal depressed. (confirm)
Last edited by Landseer; 06-29-2008 at 10:31 AM.
06-29-2008, 11:32 AM
#5
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The switches are on the master cylinder, underneath. They are a bear to replace with the master cylinder installed not much clearance for wrench turning, but doable with a 24mm stubby wrench.
Mine were corroded badly and the rubber boots were full of brake fluid.
Mine were corroded badly and the rubber boots were full of brake fluid.
06-29-2008, 12:12 PM
#7
Rennlist Member
Dean,
I checked more carefully, and S6 is the CE connection, and its downstream of the switches that the other guys are mentioning, and upstream of the bulb comparator, so its a key place to take a measurement.
S6 feeds pin-in terminal 1 of bulb control unit, and splits the power to pin-outs 9 + 12 of the bcu. Pin-out terminal 12 feeds your left stoplight; pin-out terminal 9 feeds your right stoplight. I've seen two failure modes. Sometimes the bcu gives a false bulb warning, but still passes power to the back of the car. In the other, the circuit is messed-up in the bcu so that no power passes.
If you were to fix/confirm good switches, then, you can bypass the bcu by bridging terminal 1 to 9 & 12.
Another way is to run a separate wire from S6 to the stoplight bulbs, the backwoods method.
Good luck, sounds like between us we collectively have given you some ideas.
I checked more carefully, and S6 is the CE connection, and its downstream of the switches that the other guys are mentioning, and upstream of the bulb comparator, so its a key place to take a measurement.
S6 feeds pin-in terminal 1 of bulb control unit, and splits the power to pin-outs 9 + 12 of the bcu. Pin-out terminal 12 feeds your left stoplight; pin-out terminal 9 feeds your right stoplight. I've seen two failure modes. Sometimes the bcu gives a false bulb warning, but still passes power to the back of the car. In the other, the circuit is messed-up in the bcu so that no power passes.
If you were to fix/confirm good switches, then, you can bypass the bcu by bridging terminal 1 to 9 & 12.
Another way is to run a separate wire from S6 to the stoplight bulbs, the backwoods method.
Good luck, sounds like between us we collectively have given you some ideas.
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06-29-2008, 12:50 PM
#8
Drifting
Thread Starter
Brad...from what I have been able to find out the 1980 model does not have a switch at the pedal. I wish it were that easy. Thanks though.
Chris...I will check that for sure thanks.
Mitch...it does look tight. Before I start turning and pulling I wanted to make sure I was looking at the correct item. Don't know why I can find info in the MSM about this!
Charlie...yes if you don't mind....lets swap out a switch and see if does anything.
I Love Reenlist. If it weren't for this site and the INTERNET I would not be able to own a car like this.
Chris...I will check that for sure thanks.
Mitch...it does look tight. Before I start turning and pulling I wanted to make sure I was looking at the correct item. Don't know why I can find info in the MSM about this!
Charlie...yes if you don't mind....lets swap out a switch and see if does anything.
I Love Reenlist. If it weren't for this site and the INTERNET I would not be able to own a car like this.
06-29-2008, 03:36 PM
#9
Drifting
Dean, No you don't have a brake light switch under the brake pedal. But you DO have 2 switches under the master cylinder. Either one of them can cause the brake lights to not work. If you swap a known good one with one of yours and still no lights, then try the other one. On the bad side, BOTH of mine failed at the same time....so.....it CAN happen.
06-29-2008, 03:39 PM
#10
Can you just jumper it to see if the lights work 1st, instead of replacing the switch?
06-29-2008, 03:45 PM
#12
06-29-2008, 03:51 PM
#14
Drifting
Pull down the rubber boot and expose the 2 electrical connectors. Use a wire with 2 alligator clips and attach one to each of the terminals. Push on the brake petal while someone watches to see if they work, or setup a mirror behind the car that you can see from the driver seat.