'90 Convertible Interior lights come on with no provocation

[Philbo]

So I have a new problem with my reatta :( that started over the weekend.  For some reason when it is sitting parked with the ignition off and the key removed, the interior lights, the mileage box on the instrument panel, and the lighting for the climate control and radio all come on without any provocation.  Typically these will come on when either the door handle is operated or I push the unlock button on the remote, but they are coming on by themselves.  They will also go out and then come back on a moment later.  

 

One other issue that could be related but not sure is that it rained over the weekend and for some reason the passenger side carpet became saturated.  I am not sure how this happened as I have parked in the rain many times without issue (although this time had a breathable car cover on, no idea how that would cause it though). I could not find a door cracked open or anything either.  My thought is that the moisture is causing a short, but I cannot find any moisture anywhere other than the carpet and I have the carpet almost completely dry and am still having the problem.  Any thought to get me pointed in the right direction would be welcome.

 

Everything operates normally when I am driving, it is only when parked and off that it acts up (at leas as I have noted thus far).

[Ronnie]

I'd guess the problem is with the wire splices under the carpet. The reason it happens with the interior lights is because the light socket is hot all the time. Even when the key is off. What makes the interior lights come on is them getting a ground from the BCM. The ground wires run under the carpet where there are a lot of metal splices that rust when exposed to moisture. Take a look at this how-to guide and you will see what might be going on with your car. Wire Splice Repair

 

 

[Philbo]

Thanks @Ronnie!  I will check into that.

[2seater]

This isn’t directed at the light issue directly but from what I have found in the past, the carpet may feel dry on top but it may be soaked underneath. I found this on my own car, even after sitting in storage indoors for months. It almost seems the carpet and pad combination work like Gortex in reverse, moisture in, but not out. 

 

[Philbo]

10 minutes ago, 2seater said:

This isn’t directed at the light issue directly but from what I have found in the past, the carpet may feel dry on top but it may be soaked underneath. I found this on my own car, even after sitting in storage indoors for months. It almost seems the carpet and pad combination work like Gortex in reverse, moisture in, but not out. 

 

I think I am going to pull up the carpet this weekend and just make sure everything gets good an dry. Probably I will leak test too and see if I can figure out where the water came in from.

[2seater]

If it was the passengers footwell that was wet, the only item other than window leaks would be a plugged drain in the HVAC plenum? Hard to imagine that would happen with a cover over it?

[Philbo]

So had another rain and the carpet got wet again :(.  As near as I can tell it's actually coming in through the tonneau cover.  I think short term solution will be a car cover that is water proof, but does anyone know where I might be able to buy replacement weather stripping for a convertible tonneau cover?

[Philbo]

So the plot thickens.  It rained last night and no watter got inside the car. I popped the Tonneau cover to see if I could find where the water might be coming in from. No indication that water was leaking into the trunk.  However, I noticed something I had not before.  There is a channel that runs between the tonneau cover opening and the trunk opening. And this chanel is not sealed and open to water flowing in from the rain.  There are two small holes in this chanel on either end for draining this water. Hoses connected to these holes run to the wheelwell and drain the water down under the body of the car in front of the rear tires.  My suspicion is that one of those holes got plugged by a leaf or something allowing the water to overflow the channel and leak into the trunk. My driveway is such that the car faces downhill so I am suspecting the water ran down into the cockpit under the passenger side seat.  I am going to carefully put this theory to the test with the garden hose and see if I can confirm that is what is happening.