Mystery electrical problems... 1997 Disco
 

Hi all,

I'm not the best figuring out electrical problems. I've been staring at wiring diagrams until my eyes bleed... but this has still got me baffled.

I had a sudden electrical problem where multiple items failed all at once, but I cannot find any common path between them. Maybe someone smarter than me can suggest something!

All at once, the following happened:

1. All three interior dome lights failed (dash lights still working).
2. Radio will not come on or illuminate at all.
3. Clock displays time and is illuminated, but won't keep time (resets to 1:00 every time the car is stopped or started).
4. Also, the CD player under the passenger seat sounds like it's repeatedly trying to load (there's no cartridge or CDs in it)... But it ONLY does this when I turn on the headlights etc. at night! Not when the car is started and run without the headlights etc. AND, when I hear it doing that, if I turn the radio on briefly (altho it's still not working) and then back off, the CD players stops making the "loading" noise!

All these things were working fine until this occured. The only recent change I can think of was that just the day before I'd put an LED light in the front dome light to see if it was brighter (it wasn't!). The LED worked several times before this failure, but it also seemed to mess with the "fade" effect of the dome lights, which sometimes was longer, sometimes shorter.

And, possibly related, this all happened after one or two of the doors had stood open for several hours (while I was working at a job getting tools in and out of the back, primarily). Normally when I've left a door standing open, after a few minutes the dome lights turn themselves off. This time they simply didn't come back on.

As I said before, the dash lighting is all fine and working. So are all the exterior lights, turn signals, heater/cooling fan, air conditions, power door locks, etc. And the beast is running fine, too (except for some deferred maintenance and an overheating instance, but that's another story). The only recent repair was a fuel pump replacement (separate issue and yet another story).

And the only electrical mods on the car are addition of a couple Hella running lights (working fine), an extra power circuit to charge batteries on a towed trailer, and an electric brake controller (all working fine, it appears, though I don't have a trailer to test with at the moment).

I thought maybe the MFU was at fault, but ran through the diagnostics of it and all seems fine (wipers and washers are working fine, for example). I also didn't see these particular things being tied to the MFU. ???

I've checked that all the fuses are okay both inside the car and under the hood (which none of the above have in common, anyway, AFAIK.

The only other thing of note is that I've got the black cardboard passenger side underdash panel out at the moment. I'd heard a faint "buzzing" noise under there from time to time... erratic and usually only in damp weather. I'd removed that panel trying to track it down. I don't think that noise is related though, since it's been happening for a while. But I also haven't ruled it out, since I haven't heard it lately (but we also haven't had a drop of rain here in N. Calif. in a month or more). I mention this because there's a lot of wiring there... and thought maybe something had gotten pulled loose. I've looked it over closely and don't see anything... but, who knows!

Any ideas?

Thanks in advance. Cheers!

Alan Myers

it sounds like you may have some poor ground connections...check the battery cables first, then the engine to frame ground strap, and behind the drivers side and passengers side kick panels..those are common places for corrosion...

Same issues
 

No, I haven't figured it out yet.

Did your problems also start shortly after installing an LED in that dome light? Mine worked for a day or two with the LED, then all the problems cropped up at exactly the same time. Taking out the LED and putting the standard bulb back in didn't help (that would have been too easy!)

I've also noticed that that my rear wiper isn't working... but that may be unrelated. It's been glitchy for years... has seemed related to the dash switch (cleaning it with contact cleaner and lubricant worked in the past, but I haven't tried it yet, this time).

I suspect a failed common component or a bad ground somewhere, but haven't been able to find anything common to the radio, clock (maintaining time only), and the dome lights.

I noticed that all the circuits involved are ones that should remain live when the ignition is off and key removed. (Other similar circuits such as the door locks and alarm system still work fine, though.)

I hate electrical problems like this! I guess I'm schematically-challenged.

Elec issue
 

EUREKA!

I checked that fuse... #6 on Satellite box 2... and found it blown too.

Put a new 20A fuse in and things are working again.

I thought I'd checked all the relevant/possible fuses. I think I skipped the Satellite 2 box because it doesn't appear related to interior dome lights, etc. In fact, all the docs I've got say that fuse if for trailer lights!

Go figure!

BTW, the ground wire that activates the interior lights on my driver's door is broken, too. It snapped off right at the switch, probably due to 20 years of flexing every time the door was opened and closed. I still need to fish out the wire and reconnect it, but haven't worried too much since it can't cause a short (it activates the lights by grounding them).

Cheers! (Now on to the next problem!)