1986 Fleetwood 75 Formal Limousine

A fuse sounds in order, or the actuator within the door may be bad. Do the other door locks work? If not then check the switch then the fuse then the actuators.

What about Interior light? Usualy when I open door the interior light is on. But now it does not work: Light and all doors.

plese, respond.

A break in the circuit is the only answer, but where? Have you checked the bulb? Are there any relays? Is there more then one fuse box?

I have had the interior light problem on a couple of vehicles. In both cases the switch that is activated when the door opened had a poor ground. Remove switch and ensure the contact that makes contact with chasis is clean and in good condition.

Option A: I'd find a GM factory service manual for the vehicle, get the correct wiring diagram, and trace out the possible failure points. Then I'd get attach a 12 volt light bulb and volt meter in parallel (to avoid false readings) and check the possible failure points.

Option B: Replace electrical thingies until the problem goes away.

My guess is there is a bad ground on the circuits.

Yep ground faults are most common on low voltage medium current circuits such as those used on cars. Some very tiresome faults can be traced back to a loose ground.

Check the fuse first since it's the easiest thing to troubleshoot. Hopefully the manual will tell you where the box(es) are located, and the box may even contain a fuse puller and spare fuses.

Not familiar with GM wiring so much but...

Hmmm, a little fault elimination seems in order....

You say the interior light...meaning the courtesy (fridge door) lights, not the overhead light--the ones that come on when a door opens, right? Okay.

You say all lights don't work so that eliminates a light switch--and maybe a fuse, too.

Normally:

When the doors are closed, the locks will operate; when they open the locks are not needed and need not operate. In fact, they probably need to be prevented from operating...so the doors can't be slammed with the latch(es) deployed.

When the power locking mechanism is needed, the lights are not...cuz the doors are closed.

Therefore:

My bet would be that the simultaneous, two-circuit (i.e., two-subcircuit) failure is due to a fault in an interface between the courtesy light and door lock circuits. I would look for that interface: possibly a diode (when one circuit is closed/energized, the diode biases against current flow in the other). (A way for power source sharing, and less wiring... in addition to the interlock function mentioned above!)

Try looking looking inside or under the light fixtures... (this is a hunch: start with the overhead light fixture); or tracing from interior light fuse...

When/If you find the interface, there will be the problem...is my most humble judgment. (Twenty years is about enough time for a diode to fail--which means I now have to start worrying about the diode in my pickup's light circuit... Thanks a lot!)

BTW...they were still using that Fleetwood name in '86? How about Fisher Body?

Hoping this helped...

Thanks for so sorrow analysis. I am with you. But I cannot do it myself, I will go to Bodyshop.

Re name: yes, it's Fleetwood 75

I will let you know the results, next week.

Thank you, guys.

It was just the burned fuse.

apcco