98 Discovery - no brake lights - good switch
 

Hello all,
I just purchased a 1998 Discovery and I'm trying to trace a fault in my brake lights. I started with the brake switch. It has voltage to the switch and there is continuity when the switch is closed (brake pedal pressed). I'm inclined to believe that the switch is good because I have no problems with shifting out of park. I have traced the circuit in the tail light housing and it has continuity to the plug. There is no voltage in the plug in the rear of the vehicle when the pedal is depressed. It looks like there is a problem somewhere between the brake pedal switch and the plug at the light housing. I have also checked all the fuses and bulbs and they're ok. All of the other lights in the rear work fine. Just don't have any brake lights. Any assistance would be greatly appreciated! Thanks, Elliott

There are ground points in the back somewhere near each tail light. I would clean those real well as a starting point. Also there are 2 switches on the brake pedal one is for the cruise control and one is for the lights, make sure you are checking the right one. (the cruise control switch may just be a vacuum release valve but I believe it has a plug on it as well.)

If these ideas don't work, download the rave manual (if you dont already have it) and just start following the wire from the pedal to the light and find your problem that way.

Thanks for the quick response. I will go look for these ground points tomorrow. I did see that there were two separate switches. I checked the one that also controls the shift release. I haven't jumped too deep into the rave manual but that seems like the next step. I'm just wondering where the signal goes once it passes through the brake switch. There has to be a fault somewhere between there and the light itself. Thanks again for the input.

one other thought, since you just bought the truck I would check the wiring under the dash for any noticeable changes. If someone had a remote start in the truck they could have tapped into the brake wire and caused a problem while removing the system.

This problem is ruining my Sunday. The only wiring I can see that has been modified appears to be in relation to the aftermarket CD player. Everything else looks fine. I have tried applying power to one of the brake lights and this causes the two lower ones to light up. From looking at the rave manual I see that power should come from the fuse box, to the pedal switch, then it should go to the back to the lights. I'm not sure what the capacitor called the "stop lamp suppressor" does. I've traced most of the harness from the front to back but I can't find any shorts. Does the ECM have any governance over brake lights? I never have gotten along well with electrons so if you have any thoughts please let me know and I'll try it out.

there should not be anything else involved in the circuit, if you have power at the switch then go to the next connector and check for power there and keep going back until it is gone. you should be able to find the brake wire in the drivers kick panel (may be in a loom of wires under the edge of the carpet, or behind the panel) test it there then usually (in most vehicles) it will split somewhere around the drivers seat and go to the passenger side. I would guess that since both lights are not working, the problem would be before it splits. I will check my rave manual for some places for you to look.

usually a stop lamp suppressor is just an audio filter in the path of the brake wiring (as you said a capacitor) to filter noise out of the audio system but I don't think that should be a problem.

also is this a D1 or a D2?

my rave manual (looking at a 97 D1) shows a gray 20 pin connector behind the trim panel of the left hand side rear of the roof, looks like it goes from there over to the third brake light, and down to each light. I would check that connection and for power there if your truck is the same.

also dont see any of the other lights back there (turn, reverse) going through that connector. however the rear fog lights do go through that connector which you may want to test those as well as they may not work. (the rear fog lights are just like your brake lights but I think they may even be a little brighter but not completely sure)

thanks for all of the good info. I think tracing the wire sounds like a good plan. I already started tracking it from the back forward. I'll get back on it tomorrow. If all else fails I'll just run a new wire back and "hotwire" it. I'll keep you posted.