Ok, I've got a 92 240 and it's starting to act very weird electrically:

- If I activate the front windshield wipers, the rear nozzle activates (sprays)
- if I honk the horn, the rear wiper activates
- the windows don't roll down, unless I flip the a/c switch, then they'll work for a second
- The master door lock function is intermittent; works sometimes, other times it doesn't


That's all I have for the moment. I'm hoping it's just relays, but this all started at the same time. Any thoughts?

 

those sorts of crossed connections often can be traced to a bad ground.

the 240 dashboard stuff is all grounded on either side of the transmission hump just forward of the gear shifter. on either side of the lower stereo cubby. some stuff is grounded on the left, other stuff on the right (this is to keep noise from power consuming devices from interfering with electronic devices such as the fuel injection computer).

 

How do I isolate this ground problem? I've got an ohm meter but I don't know how to use it to be honest.

 

probably easier find someone who knows the basics of electricity than for me to try and explain it in abstract terms.

 

Wow, and I thought I had issues with my erratic MPH gauge. Please keep us informed smshnick. I'm curious how this one turns out.

 

smshnick, do you have a sedan or a wagon? If a wagon, check the wires running through the hatch hinges. They wear and break over time; and at least one is a ground. An additional grounding wire fabricated to go from the hatch to the main body was a cure for my issues, even after replacing the harness wiring there.

 

he's got a wagon, cuz he said rear wiper and sprayer, and yeah, wagon hinge wiring is a big culprit on these sorts of problems.

 

I did re-ground the hinges a month ago, so I'll check there to see if maybe one of them failed. I did take the center console apart and found a loose ground wire on the upper right portion of the center stack (behind the climate controls). That did seem to fix my power window and power door lock function. I'm still having this weird problem with the wipers - when I activate the front wipers the rear nozzles sprays, and when I activate the rear wiper the front nozzles spray. Plus, when i activate the horn, the rear wiper activates. I've checked the other ground by the transmission tunnel and that looks to be o.k. SO, I'll double check those hinge grounds and see if that helps. Thanks all!

 

also check the ground that comes off the horn switch in the steering column.

the two horns are wired in parallel, diagram says with black wires. one of them has a yellow + black wire going to it, the yellow one is power from fuse 2 (hot in accessory or run). the black wire goes to the horn switch ring, which grounds it when the horn is depressed.

 

the washer pumps are grounded on the right fender just behind the headlight, and right next to the washer bottle. common site of corrosion.

good test for these grounds is to connect a volt meter between the battery - terminal, and the black wire at the washer pump motor, then have someone turn the pump on... if you see any voltage above like 0.05 volts, you've got a bad ground.

 

there's also a key ground near the left rear wheel hump under the trunk carpet...

 

I cleaned a bunch of grounds and tightened a few that were already pretty tight, and now the radio doesn't work. I also didn't fix the horn/wiper/washer issue. There's a ground by the transmission tunnel that I tightened so I'm hoping that's it. I'm about ready to take it to a real mechanic, have the car fixed and sell it.