Interior light issue

[az_max]

I figure I would update this thread for future reference. Things got worse. One night my alarm went off at 3am. I spent the next day tracing grounds and still couldn't figure it out. So I decided to pull the horn relay so that at least it wouldn't wake my neighbors up and instead just treat them to a light show. This worked great until last week when some asshole didn't defrost his windows and merged right into my lane...and there I was, without a horn. This had to end.

So after almost 5 months, I decided to take another stab at the problem. I traced each ground. All were good. I traced wires going to and from fusebox (the best I could) to ensure none were broken. I pulled the fusebox and took it apart. There I found significant corrosion going into the connector for the MFU. (See photo below.) Aha! That has to be it, since all functions that didn't work are MFU related. I cleaned it up, re-assembled and put the fusebox back together.

It still didn't work. Completely frustrated, I started to push the fusebox back into place and quit for the day (again). Suddenly, I notice my interior lights working. I opened and closed the doors and made the lights go on and off just to feel good for awhile. I then continued putting the fusebox back into place and noticed the lights were off. Then on. Then off.

Aha again! Bad connection. I wiggled every wire going into the box until I narrowed it down to one specific connector going into the back of the fusebox, then the specific wire. It then took me 30 minutes to figure out the exact way to apply pressure on the connector to make the lights work on demand. Now I needed to decide was it the connector or the fusebox? Since there isn't much room to work, I made jumpers for all 7 wires in the connector. I could apply pressure on the brown wire at the connector end and the interior lights would still work. Applying pressure on the brown wire at the fusebox end make them fail. It was the fusebox.

I got a replacement fusebox and 15 minutes later was not only greeted with interior lights but also the nice "ding ding" sound when you leave your headlights on. Bonus. Heated windshield works too.

Who knows what failed in the fusebox since it seemed pretty simple. Just copper runs going to and from wire connectors. No circuit board or anything fancy. It probably was a ground within the fusebox itself. But now I know that when a fusebox fails, it just doesn't "fail". It can give mysterious symptoms.

Glad you got it figured out.

 

[jeepfiend]

Nice work and great persistence!! Sometimes you gotta ask why we like these silly British cars so much?!? Even with the gremlins, I can't get enough of them!

 

[your pal]

Was that the fuse box under the dash or the one under the hood?
I have alot of the same symptoms and have checked grounds several times with no change. Also were did you get a fusebox from. I think I may try that as well since nothing else has worked.

Rico

 

[skippy3k]

It was the fusebox under the dash. Will Tillery or Paul Grant can hook you up with one.

 

[Ed Cheung]

That good news for me as well, I got the interior light problem just like yours. Now you figure it out, so I know which direction I should be heading.

 

[sven]

Good troubleshootin'.

Makes you wonder how that fusebox got corroded to begin with.

 

[paxton]

I've got a similar problem, on my 93. Mine has also had the airbags removed, and replaced with springs.

When I press and release the switch on the door jamb, the relay clicks. Sometimes after closing the door and locking it, a relay clicks a few times. (Sounds like it's in the same area, but I can't be sure it's the same relay.)

My lights come on when I open the door. But when I close the door, the lights don't turn off. It ran by battery down over 4 days.

Anyone else had this kind of (related) problem, where the lights stay on? My fusebox is up top in the dash, so it'll be easier to get to... Happy thoughts, happy thoughts...

 

[skippy3k]

I believe 93's have their own interior light relay, which is the click you are hearing. 95's did away with them. I would try replacing or swapping that relay and see what happens.

 

[paxton]

Finally decided to fork over $80 for that relay, and sure enough, the lights go off as expected.

Success!

Another added benefit: my rear wiper, which never worked before, now randomly swipes :banghead:

 

[TigerDan]

By swapping relays, I got the interior lights to work normally in my '94...but the battery still drains unless I pull the fuse for the light.

Effing Lucas crap. Ya gotta love it!

 

[92rrrandall]

For a while my 92RR would drain the battery during the week. When I would go to start it on the weekend...it would not. Was able to quickly narrow the drainage problem down to the circuit that ran the interior lights.

There are quite a few devices connected to that fuse. Put some serious thought and trouble shooting into it. Tried removing the wire which goes to the drivers seat buckle(seat belt warning) and the battery has not drained in a year. Not absolutely 100% certain, but battery drain was a constant problem before wire was removed, and has not been a problem since. The seat buckle light/buzzer do not operate after you remove the wire.

That wire and the seat buckle switch was another add-on th the RRC for the NA market.

Randall