AO

I'm stumped... I think.

Last night I was installing the Champagne illuminated sill kit, and was just putting the 2nd (passenger) into its final spot when all the interior lights went out. WTF?

I checked all the fuses and they all check good. I'm pretty sure the interior lights fuse is #41 on the '91 GT, but it checks good and I tried a different fuse to make sure. I checked a number of other fuses while I was there just to make sure. They all look good.

I'm starting to suspect the alarm module which also has the interior light relay IIRC. I've tried a few battery resets, locked and unlocked the car several times but they don't seem to want to come on.

I checked voltage at the fuse, at that's good, but no 12v at the door lights.

What am I missing?

Jadz928

Door switches shorted. Common. There's a sharp edge where the wire passes thru the chassis that chafes.
Did you tie your sills into these?

AO

Is that a fuse between the two plugs on the alarm module?

AO

Yes... they're tied into the door lights.

So you're saying I should pull the pins and look for a broken wire?

Jadz928

You got it!

James Bailey

The early pin switch just grounds to complete the circuit so are the later ones hot ?? because a chafed wire on the early car if it grounded anywhere would cause the lights to be on....

Jadz928

Anecdotal only, Jim, but my '84 had a chafed wire which caused a flicker.

I believe it's a ground, and the plunger switch is normally open (door open, light on).
So switch to ground is normally closed (door closed, light off)... which is the same thing the chafed wire is doing.

WallyP

I think that the door switches are NC (Normally Closed) so that when the door is open (switch not activated) the switch is closed, grounding the brown/white wire (switched ground), thus turning the interior lights on and enabling the hatch release circuit.

Closing the door activates the switch, opening the switched ground circuit.

If the brown/white wire shorts to ground, the lights will always be on. If the wire breaks, the interior lights will not come on when that door is opened.

If your lights won't come on with either door or the hatch open, it is not a broken wire at one door.

Try switching one of the lights on with the switch at the light. If it doesn't come on, the problem is with the power supply circuit.

AO

That's the issue. No 12V at any of the lights. none of them come on either manually or when opening any/all of the doors.

The only thing common (besides the fuse which is good) is the alarm module which controls the interior light delay.

So it looks like I get to pull the passenger seat today... not what I was looking to do.

Jadz928

Cleary, I don't know wtf I'm talking about. Sorry 'bout that.

Thanks for proper clarification, Wally.

Sorry AO it wasn't a simple solution.

Mrmerlin

I checked all the fuses and they all check good. I'm pretty sure the interior lights fuse is #41 on the '91 GT, but it checks good and I tried a different fuse to make sure. I checked a number of other fuses while I was there just to make sure. They all look good.


AO look at fuse # 25 thats for interior lights per 928gts fuse chart for a 91

AO

MrMerlin wins the prize. Thank you!

Fuse 25 was the call. The chart in my car (on the back of the wood) says fuse 25 is for the hatch release and that was working fine... Looks like I need to print out and carry the one from 928 Specialists.

All lights work fine - well except for a few of the flickering LEDs.

Mrmerlin

Glad I could help

Bill Ball

Congrats! You are the first person to ever admit that here, but you are otherwise in good company. I once wrote that the knock and Hall sensors are on the same circuit because both weren't working when I found the knock sensor plug had popped open and both started working when I plugged it back in. Oh, well.