For all you electrical gurus, here is one I've never heard of before

I changed out the electric window switches w/ some boneyard replacements. The first time I tested them, they worked great. The second time, the overdrive light came on when I tried to roll the windows down. Now the windows work fine (no OD lights either) but the overdrive won't engage. Instead, I get a buzzing sound from behind the dash, which I'm guessing is the newly-fried overdrive relay (I'm assuming there IS an overdrive relay)

My questions are (1) Where is the overdrive relay located and (2) What wierd electrical gremlin causes the overdrive to be connected to the window switches (Where is the best place to start searching for the cause of the problem?)

Thanks

Although I won't get around to fixing it until next weekend, at least I know where to start. It's amazing that I can post such a thing and get expert advice within hours. Thanks to all!

Bob

Hello Bob,

I have a 'green' volvo 1981 wiring diagram manual. Looking at both the over drive & window lifts. I can't find any possible situation where one can affect the other.

You mentioned that you get a buzzing sound behind the dash. Is this with the over drive switch engage or is it constant?

Also the location of the over drive relay is behind the center vent.

I believe you can access this from the golvebox or by removing the center faceplate.

Any further information would be helpful. I can help trace this using the wire diagram.

Good Luck.

Bob-

The OD relay is accessed by removing the glove box and looking to the left. The power window relay is about the same as the main and fuel pump relays. It is mounted on a rail that runs between the glove box and the instrument cluster area. When you hear buzzing it can mean that the relay is on, off, on, off, etc. The PW relay is energized while the key in position II.

Look at the OD relay, it's easier to get at. Pull the relay out of its base, and see if the buzzing stops and if anything else changed.

The relay base should have one black wire that is the ground. The 1984 Volvo WDM shows it to be terminal #31. Follow that black wire to where it grounded, and it's likely the ground wire from the PW relay is at the same place.

There is a gang of black ground wires screwed on to the control panel frame on one of the upper right mounting bolts, it may be one of them.

Make sure all grounds are good sound connections. Boy and howdy you can get weird things with poor ground connections.

Good Luck,

Bob

:>)

(I'm) Too lazy to get the schematic out. But the OD relay is accessed by removing the glovebox,it in the center to your right. Sounds like a bad ground.

I meant to the driver's right. Left hand as viewed from the passenger seat - near the center heating duct outlets, right behind the center console.