1991 Grand Marquis dash, rear, side lights out

I have a 1991 Mercury Grand Marquis and the tail lights, dash lights and side markers, plus those "limo" kinda lights between the doors went out last night. I checked the manual, and it clearly states the fuse to change (inside the car under the dash) which is #4 for the particular set of lights that are out. I checked fuse #4 which looked okay, but went ahead and changed it out with a known good fuse. The lights are still not working. Any other suggestions where to look for a problem?

You could have a short somewhere, but I'd also check the multifunction switch (turn signals, brights, etc). Had both a 93 and an 86; the switch went bad in both of them. In the 93, the taillights would either go out or short out, and in the 86 the headlights would go off or flicker, and the engine would cut off when I tried to put on high beams. I didn't have the opportunity to check other lights, but they may have been affected also. The switch is about 70-80 $$ and an easy install.

-edit- with all the stuff going through the switch, there's alot of things that could be affected.

Hope that helps.

You could have a short somewhere, but I'd also check the multifunction switch (turn signals, brights, etc). Had both a 93 and an 86; the switch went bad in both of them. In the 93, the taillights would either go out or short out, and in the 86 the headlights would go off or flicker, and the engine would cut off when I tried to put on high beams. I didn't have the opportunity to check other lights, but they may have been affected also. The switch is about 70-80 $$ and an easy install.

-edit- with all the stuff going through the switch, there's alot of things that could be affected.

Hope that helps.

FRED! This is exactly what happened to my 90. However, when the engine cuts out, I can't start it again for a little while. Sometimes a day, sometimes sooner, and when it doesn't start, I mean I get no lights, no sign of ignition, nothing. Go back out an hour later, and I have lights, it starts, and I can take er out again. Could this stll be the switch????

It could be, but it may also be something called the "Hall Effect Sensor" which is contained in the distributor. I believe you've got the 5.0 efi engine, right? If so, then the hall effect sensor could be your problem. In the 86 I had, it went bad, the car died on me, but started right up a little later. Replaced the hall sensor, then it was all good.

You have to remove the distributor to get at it, and so it's not a real easy fix. Fords (and Mercs) with the 5.0 are famous for it.

Hi Again,

Today I tried something else. Got in the car, had lights and everything. Put the ignition to on. Turned the lights on and went to flic the high beams and everything died, without the car even being on. Now, unable to start. Could this still be the Hall Effect Sensor if the car is not running????

Definitely sounds like the high beam/turn signal switch. I'd replace that, then see what the situation is. Like I mentioned, the multifunction switch can cause a bunch of very strange problems, and mine made the car cut off as well as shorting out and dimming lights.

also I would look for a ground prroblem.

Any luck? What is the diagnosis?