Electrical Gremlins - short IN fusebox?

[Huw Powell]

> After getting my 1990 Coupe back on the road after a fender bender, I
> am having some electrical problems.
> 
> I drove the car for about a week after being repaired and painted
> when the #12 fuse blew.  I replaced it and it blew again after about
> 5 minutes.  Now it blows immediately when the car is turned on.

Never replace a blown fuse without first determining why it blew.  The 
extra cycling can cause a lot more problems down the line.  Anyway...

> This fuse controls many things like the instruments and auto-check
> items.  While troubleshooting the problem I unplugged the connector
> from the bottom of the fuse box.  When I did this, I found that the
> non-hot side contact in the fuse box was grounded!  It did have about
> 150 ohms resistance but it still has continuity.

According to my fuse box diagram, #12 goes to several circuits, through 
*two* connectors, B (black) and C (blue).  Did you unplug both of those?

Also, 150 ohms to ground will only draw about 1/10th of an amp at 12 
volts (V=IR).  I don't think you've necessarily found your problem yet.

> Any suggestions?  Anyone ever hear of a fuse box going bad
> internally?

Yes, I had to replace the one on my 90Q after killing its innards by 
holding down the cig. lighter for an extended period of time (don't ask...).

And of course the ancient underdash box my coupe came with is a 
patchwork quilt of repairs and workarounds.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/