without the car in front of me just a wild guess.

The fuse panel sections are connected by a brass rivit at some point. This connector failed partially. It you use the headlight sw it feeds backflow current to other connected light circuits into the weak fuse panel.

I'd at least do a volt measurment with one of these down stream circuits with the bulbs attached to create a current draw. Or how about creating your own panel jump?

So the brass rivit is where you test to see If it's going to ground?

I have nothing to add but hope you figure it out and post the result just in case I have to deal w/ it. Some of my wiring is chewed up and I have visions.......bad visions of stuff like this this.
If you've done any work on the car recently that may jiggled some wires around, you might just check there. Had a 2002 that died a few days after I had cleaned the engine compartment and had to shift some wires out of the way. So I started jiggling some wires around and got it started. Later, I went through a bunch of connections checking a cleaning them and never had the problem again.

Good luck.

Kiss method ( keep it simple stupid ) please try all the simple things 1st !! then we will all move on to the next step.......please do the grounds and report back

the brass or copper buss connector is for positive. Only a wild guess that this is contributing. This connector is one of those crazy problems waiting to happen.

It's directly below the red relay at the top of fuse 3 & 4 from the left. The pic is from my 1977. Don't know about other years.




http://forums.pelicanparts.com/uploa...1154109791.jpg

Some of the wiring in these cars looks like it was an after thought. It's clear that the wiring of the short hood cars migrated itself in the the mid years.

That brass bar in RoninLb's picture looks like a problem indeed.

David Duffield

So have you checked the tailight bulbs yet?

Ditto check the ground. There is a grounding terminal behind the dash near the driverside hood strut. Many of the dash electronics ground at this point. It's accessed from the trunk.

When you activate a switch that has lost ground it tends to seek ground though the path of least resistance. This often causes other electrical components in the loom to act strangely.

Ground wires are brown in general.

Every early car I have owned has had some type of burned wiring. Dash lighting is often a culprit. I would check for any melted wires behind the dash.

The fuel pump receives current from the ignition switch which feeds current to the fuse on the fuse block and from there to the pump. I think it's fuse number four but can't remember for sure.

Ok,

there has been mention two times about the possibility of rear bulbs being the culprit here. I know that MB Sprinter vans have problems when one puts a different bulb in the tail lite. Not sure if its a German thang but I did have a problem with my backup lights. didn't have an OEM replacement so I put in one 7057 bulb.

Kerpow, blown fuse. Changed out the other bulb so that both bases where metal (not one metal & one brass) and I have no more blown fuses. Though I do have another eletrical problem and wonder if the non OEM bulbs are the cause.

here's the link to my prob...

cutting out?

Speaking of grounds...

Should there be (at least on my 80 SC) ground straps to the front and rear bonnet lids? Why?

thanks,
Jim

Check your fuse blocks first. I had a similar problem. I did all the troubleshooting and found this, the previous owner had messed with the fuse block connected some by-pass fuses, etc. it was a real mess. I replaced all three fuse blocks, problem solved. Check the pic below.:D


http://forums.pelicanparts.com/uploa...1154123694.jpg

I think the ground might not be good behind the dash, it looked and felt loose......i will let ya'll know