Strange electrical problems with 91 Q45

[DQuintana]

Hello,I have a 91 Q45. Recently I’ve been having strange electrical issues. It started when I would press on the brake pedal. The display lights for the fan and temperature would dim. I then checked all of the exterior lights and noticed that the tail lights were not working. I checked the fuses and found the “illum” fuse needed to be replaced, which I did, and that corrected the tail light issue. I also noted that one of my backup lights is out. I have not yet replaced that bulb. Otherwise, all other exterior lights are working properly. I’ve been driving when it’s dark this past week, and I’ve noticed that the dash lights aren’t working. However, sometimes they come on while the brake pedal is depressed (and sometimes they don’t). Last night I noticed that the display lights for the fan and temperature remained steady when using the brake during part of my drive, but then began dimming again later in my drive when I used the brakes. Does anyone have any ideas as to what may be causing this to happen? Thanks!

[qsiguy]

The first thing I'd be looking into would be a bad ground somewhere or a common voltage source for those particular circuits. Do you have the FSM so you can follow the wiring diagrams for those systems and try to find a common ground or power point for them?

I have the '94 model diagrams but I'm not sure if they will match or not.

[goody90q45]

Check the bulbs and sockets in the stop lamp modules. I'd guess that one of them has burnt through or melted.

[DQuintana]

I changed all of the bulbs in back. That took care of the problem. THANKS!I noticed that the end of every bulb (the little round bump on the base) was flat, as if it were melted. Is that normal?

There is one other problem I'm having that I was not aware of before. The seat adjustment buttons on the driver's door are not working. They work on the passenger door. The driver's seat moves back when I turn the car off and it moves forward when I start the car. Is there a fuse for the buttons on the door? I looked for one under the dash and under the hood by the battery and did not see one. Any ideas? Thanks!

[goody90q45]

I changed all of the bulbs in back. That took care of the problem. THANKS! I noticed that the end of every bulb (the little round bump on the base) was flat, as if it were melted. Is that normal?

Unfortunately it is normal, for the 90-93 Q's at least. Every two-filament bulb and socket I've seen has been in some stage of meltdown. The single filament bulb holds up pretty well. You replaced the bulbs, hopefully with OEM or Sylvannia long life (LL)bulbs, but did you also exmine the sockets they plug into? The entire stop lamp module pulls out and unplugs, with no tools required, making it easy to check. If the bulbs are melting, the sockets are probably melting also. Take a look to make sure or the problem might come back soon.

The seat adjustment buttons on the driver's door are not working. They work on the passenger door. The driver's seat moves back when I turn the car off and it moves forward when I start the car. Is there a fuse.....Any ideas? Thanks!

There's fuses for the motors but I don't believe the door-mounted seat controller has a fuse. If the motor is working when you put the key in and out then chances are the controller is shot. I have a couple of spares and will send you an email.