Calling all Electrical Wizards

[356robo]

Here's my problem regarding the interior dome light on an 83 944.

Light works fine on "all off" and "all on" positions. The problem is on the light position that activate the door switches.

Light is on with either door open.

Light only dims slightly with both doors closed.

Seem like a bad ground, but where?

Thanks in advance,

Rob

[Cocacolakidd]

Check door switches to make sure they are closing completly - they may be sticky. New switches and rubbers are not expensive if they are necessary.

[Rasta Monsta]

There is also a switch on the passenger side hatch strut. . .you can unplug it and see if your problem persists.

[wild man]

Originally Posted by Rasta Monsta

There is also a switch on the passenger side hatch strut. . .you can unplug it and see if your problem persists.

Isn't that one just for the hatch compartment light?

[wild man]

Originally Posted by 356robo

Seem like a bad ground, but where?

On the contrary - seem more like "too good" of a ground.

In other words, the light is finding a path to ground when it shouldn't be. The door switches ground the wire going to them when the doors are open. One of them would be the most likely culprit. Otherwise, maybe a chayf'd wire.

[Rasta Monsta]

On both my cars, opening the hatch turns on front and rear courtesy lights.

[356robo]

UPDATE!!!!!!!!!!!!!!!

Both door switches are fine.

I located a wiring diagram and determined that the front interior light shares a ground path through the rear hatch cover switch. When I moved the hatch cover up and down, the front interior light flickered.

I could not see the rear hatch switch, so I disconnected both wires at the bases of both hatch cover struts thinking maybe one or both serve as ground wires. I did not know they serve the defogger. Bingo, the front interior light now works properly with the door switches and the luggage compartment light also lights with the doors opening. But, the luggage compartment light does not light with opening the rear hatch cover. Not yet sure about the defogger heating up.

I now have properly working front interior light.

Interestingly, I found 12 volts at both wires that connect to the bottom of the struct. I would have thought that one side would be 12 volts and one side would be ground.

Rob

[wild man]

Originally Posted by Rasta Monsta

On both my cars, opening the hatch turns on front and rear courtesy lights.

Ok, it looks like mine is messed up also, then. The back one isn't working at all, and I usually only switch the front one on (manually) occasionally, but it does NOT work on auto setting.

FYI: If both sides of fogger wire are at 12V, that means that one side (don't which one, without testing it) will be grounded by the switch when fogger is turned on.

[smokin_944]

Originally Posted by Rasta Monsta

On both my cars, opening the hatch turns on front and rear courtesy lights.

Now look at what you did. This problem has been annoying me for the last few months. I don't get both lights coming on when I open the hatch... Here we go again,lol.

[cwiert]

just to be clear, when the interior light (by the rear view mirror) is switch to Auto, it should go on when? with both doors, and the rear hatch??
I'm having a similar problem. The light goes on when switched to "on" and off when switched to "off", but stays on when switched to "auto". i inspected both door switches, and they look good. but i didn't look at the rear hatch switch. hmmm.

and what is this "passenger side hatch strut" that Rasta mentioned???

[cwiert]

ok, i just went to my car to look for this rear switch and couldn't find it. if there is, in fact, a switch on the rear hatch that controls the interior light, can somebody tell me where it is? Thanks.

[356robo]

Cwiert,

To start, I had the same symptoms. I too looked for a switch on the rear hatch. I disconnected both wires to the defogger, thinking one or both may be switches. Well, by disconnecting the two wires to the defogger, the front light and the rear light now work when either door is opened. This tells me that the ground for lights use a common ground with the defogger. The rear light comes on with the front light when the doors are open but neither light works with opening the rear hatch. Getting the defogger to work and the rear hatch to operate the lights is my next challenge. For now, I'm willing to live with it the way it is.

Rob

[cwiert]

hey rob...
oddly enough, that worked. i disconnected the defogger wires and then my interior lights worked in conjunction with the doors. like you said, both lights work with the doors, but not with the rear hatch. but both lights worked manually before, but now the rear one only works with the door open. i used to be able to turn it on manually... but not anymore. strange stuff. but at least they go on when the doors open now... it's better than it was before. thanks.

[Pops944]

Rear passenger strut is the location of the hatch "switch". The 'cup' the wire is attached to has a finger inside that when the hatch is closed the cup slides over a 'spacer' that lifts the finger to break the ground. When the hatch is opened the cup slides on the strut and the finger wipes the strut rod providing the ground for the circuit. If it isn't working right, try cleaning the strut in the area of the cup with alcohol and check the finger is pressing against the strut. The door switches do wear out and are easy enough to replace. I had problems with both front and rear light switches working right. Took them out, cleaned them with alcohol, and light sand paper. Now they all work like they should.

[cwiert]

Originally Posted by Pops944

Rear passenger strut is the location of the hatch "switch". The 'cup' the wire is attached to has a finger inside that when the hatch is closed the cup slides over a 'spacer' that lifts the finger to break the ground. When the hatch is opened the cup slides on the strut and the finger wipes the strut rod providing the ground for the circuit. If it isn't working right, try cleaning the strut in the area of the cup with alcohol and check the finger is pressing against the strut. The door switches do wear out and are easy enough to replace. I had problems with both front and rear light switches working right. Took them out, cleaned them with alcohol, and light sand paper. Now they all work like they should.

Thanks Pops,
I also see something similar to that on the driver's side strut. do both sides do the same thing?

[356robo]

Cwiert,

I'm happy to have helped. Now we need to figure out the hatch system. I'll take Popps advice and clean & inspect the struts.

Maybe Popps can help with this. The two leads to the window defogger both read 12.5 volts. Are really both intended as power supply?

Rob

[Pops944]

The wire on the passenger side (cup at base of strut) is grounded when the hatch is opened, thereby completing the circuit for the lights. The wiper shown on the passenger side strut is what lifts the wiper to break the circuit when the hatch is closed. That lead always has 12 volts on it (until it is grounded). The other side lead will only have 12 volts when the defroster switch is on. It will conduct the 12volt up the strut rod to the defroster elements, and the circuit is completed at the passenger side strut which is grounded all the time. If the defroster doesn't work things to check are; 1)the defroster elements themselves to ensure no broken or cut paths, 2) the defroster relay, 3) the defroster switch itself. Hope this helps.

[cwiert]

huh...those pics are interesting. i wonder if a PO replaced the struts in my car and put them on the wrong sides, because my car is reversed. My driver's side looks like the pic on your passenger side and vice versa. on my car, that could have been where the problem started.

[Pops944]

Okay then.... with both strut leads unplugged from the struts, check them for 12volts. There should be 12volts on just one lead if everything else is turned off. If this is the case, momentarily ground that lead and see if the lights come on. If so this lead should be on the strut that has the cup type wiper (passenger side on my car). The other lead should have 12 volts on it only when the defroster switch is turned on (ignition must be in either aux or run position). That wire should be on the strut that looks like my driver side. If the wires work as described and your struts are reversed you can guess what to do next. Hope this helps. I know I'm still chasing gremlins from po's adding/modifying the wiring harness under the dash and in the engine compartment. I'm slowly getting things to work right, but it is slow.

[cwiert]

Hey Pops,
Yeah, you were right... again. The PO must have put new struts in and reversed them. Because the passenger side lead was 12volts. When I connected it to a ground, the lights went on. So it looks like I'll be swapping the struts and then all my int lights will work as should. ya!
I couldn't get the 12 volts on the driver's side wire for the defroster though. I out the ignition on, hit the button, the light on the button illuminated, but I just wasn't getting the power. I'll check the fuses, but honestly, the defroster isn't a big concern right now...that can be a day 2 project. Well, I'm off to try and figure out how to remove these struts. Thanks again for the info!