[lleroyb]

Can anyone tell me where the bulb fail sensor is on a 1987 240?

 

[bobonut]

Under the dash on the drivers side. Red canister looking item

 

[lleroyb]

So, I found the sensor under the leading edge of the dash left of the wheel. It is held in place by a spring steel clip. Pull it loose and the sensor drops down to where you can hold onto the socket and pull them apart, no tools required.

The bad news is that the problem still exists. When the key is off or on accessory everything is fine, step on the brake pedal, the lights come on, step off they go out. With the key in the run position, the brake lights come on and stay on until you turn the key off of the run position. Looking at the diagram in Chiltons I see no other possible culprets other than the bullb fail sensor which I just replaced.

Any suggestions

 

[bobonut]

are your headlights/tail lights on when the key is on? If so you may have a ground problem. If you have trailer wiring, that may cause it also.

 

[lleroyb]

It acts the same with the headlights on or off. As soon as you step on the brakes with the key to the run position the brake lights come on and stay on, somtimes. Very frustrating. No trailer wiring package and we bought the car less than a year old 22 years ago or so.

Lou

 

[bobonut]

probably a bad brake light switch. It does happen from time to time. It's been off and on thousands of times

 

[lleroyb]

I don't see how it could be the brake switch since the behavior is controlled by the ignition key. I finally started making progress by listening for sounds of relays that are activated by depressing the brake pedal. With my son's help I found three relays that were changing state when the brake pedal was depressed. The first is the fuel pump relay behind the glove box. The overdrive relay was also clicking away when the brake pedal was pressed. Removing them did not cure the problem. Finally we located another relay under the driver's side dash near the firewall. When I removed it the lights started acting correctly again. Nothing seems to not work but searching for the part number I read that it might be the rear window defroster timing realy. I can see why it would be connected to the key but have no idea why it would be related to the brakes. The relay is white, about 1"x1"x2". Anybody know for sure what it does?

 

[bobonut]

you have a wiring problem. Check the fusebox for any wiring that does not belong there. For example, aftermarket radio wiring etc. A wire may be touching one fuse to another. The brake lights have nothing to do with the ignition switch. they should work without the key. totally independent circuit. check your tail lamp grounds for breaks or corrosion.