Where is interior lighting relay?

February 10, 2011, 09:16:27 AM

A friend of mine has an 87 TC that is having a problem with the interior lights. When he opens the door the lights do not go off. He said he was told there is a switch/relay that controls the interior lights and tells them to go off. Its not the door switch because it does function. When you open the doors the interior lights come on, however they dont go off. Does anyone know where this switch is exactly?

Where is interior lighting relay?

Reply #1 – February 12, 2011, 09:09:21 AM

If I recall correctly, there's an illuminated entry module in the trunk under the package tray. Now, my car's an 85, and my memory's not the greatest on that, but I think that your problem may be related to that if you're positive the door switch is good.

Where is interior lighting relay?

Reply #2 – February 12, 2011, 03:47:35 PM

When do they go off now?

They have to go off eventually, or how else would you know they come on when you open the door, heh...

Where is interior lighting relay?

Reply #3 – February 12, 2011, 11:10:45 PM

I know the circuit does pass through the headlight switch at some point. That's how the dimmer turns on all the lights. Don't know about the relay though. Sorry.

Where is interior lighting relay?

Reply #4 – February 13, 2011, 02:20:20 AM

starting on page 108 of the EVTM per link below in my sig.

Illumination will not go off if either conditon is true
-door is open
-the dimmer switch on the head lamp switch console is roll up to the click where it keeps the dome light on.

There are four parts to the circuit,
-illuminated entry module
-illuminated door key lock cylinder
-door latch "leaf" switch
-wiring harness

The relay you seek is inside the illuminated entry module.
-If the handle is held in the UP position, the timer circuit will still turn off the lights. The logic circuit is built like this so you do not drain the battery.
Having said this, it pretty much eliminates any of your door Leaf switches involved in detecting handle motion or insertion of a key.

First lets rotate the dimmer switch to a new position like down some. You could have a faulty dimmer rheostat causing constant power being applied to the illumination module.

testing
remove the connector from the illumination module locted under the package tray but inside the trunk.
-verify headlamp dimmer rheostat is not rolled up to the "click" where the dome light is now on.
-verify your fuses
-Illuminated entry with Keyless entry- your module will have two connectors.
-the top connector is illuminated entry (as viewed mounted in the car)\
-the bottom connector is associated to keyless entry
-with the connector clip "UP" and facing you, the pins count left to right 1-8

Steps 4 or 5 should be problems associated with the front doors / switches.

1-connect test light from pin 8 to ground. with ign sw in on or off, test light should glow.
==if not, trace the light green/yellow wire back to fuse panel for the problem.

2-connect test light from pin 7 to ground. test lamp should glow when ign sw is in ACC or run and go off when the ign switch is turned off.
==if not, trace white/purple wire back to the fuse panel for the problem.

3-connect jumper wire from pin 6 to 8. with doors closed, the interior courtesy and door key lock cylinders should be on.
==if not, trace the black/light blue wire back to source for the problem.

4-connect jumper wire from pin 4 to 8. Both door key lock cylinders should be illuminated.
==if not, trace the black/pink wire to the door lock cylinder. check for continuity from the door key lock cylinder pig tail connector and the other end of the wire at the illumination entry module.
==if wiring is good, then at the door key lock cylinder, check the pig tail connector inline resistor for 135 to 198ohms. if good resistance on inline resistor then replace door KEY lock cylinder.
If resistance is bad the replace resistor in the factory harness.

5- connect ohm meter from pin 2 to ground. Meter should show open or greater than 10,000ohms.
Operate each door handle one at a time holding it in the up position. The ohm meter should display a reading <= 50ohms.
If either reading is incorrect then trace out the white / light blue wire to the latch leaf switch and repair.

6-connect test lamp between pins 1 and 8. the test lamp will glow.
==if not, trace out the black to ground and service.

Where is interior lighting relay?

Reply #5 – February 13, 2011, 02:35:13 AM

The headlight switch and either door open switch can turn on the interior lights with no relays involved.
If you have illuminated entry feature:
Raising either door handle will cause the illuminated entry timer to turn on the interior lights and the door lock cylinder lights for thirty seconds.
If you have keyless entry, it can turn on the lights.