95 850: electrical Gremlin unsolved

[CIK7]

I suspect this: https://www.fcpeuro.com/products/volvo- ... 60-9447803

Do you have a spare you can swap in to test?

I suspected that was it at the beginning. I swapped in two different ones from a '98 Volvo P80 model. That didn't fix it. However, Robert Spinner told me the 98 models are not interchangeable because they have an extra pin. So no, I think I would have to have a 93-97 ignition switch to hopefully fix it. I do not have a spare 850 unit.

[CIK7]

I installed an 8-pin ignition switch and it appears all the buzzing electrical issues suddenly have disappeared. However, I'm not going to say anything as to whether it is completely solved yet because I've said that so many times before. pending update.

[CIK7]

The ignition switch seems to have restored the majority of the electrical malfunctions. Now the next thing I think I'm dealing with is either the P&P switch or the shift solenoid. The 'shift up' and a check engine for 'vehicle speed sensor circuit A' (vss) are the errors.

[CIK7]

NOPE the ignition switch didn't do it. J relays didn't do it. I'm going to inspect the wiring around the ECU box, under the wiper cowl, and possibly inside the looms. Must be a break or short in the wiring. However can the PNP cause such weird things?

[CIK7]

Update

I discovered that there might be two separate issues. As you might have read in this thread, the headlights, gauges, wipers, and horn are random when the electric issue happens.
On Friday, I took a trip with a neighbor in the 850 to Dallas to pick up the new car that I teased in the 'car talk' forum. At one point, I accidentally bumped the wiper stalk. That immediately moved the wipers 1 inch. It also caused my car to stall in the middle of fast heavy traffic. I quickly put the wiper stalk back to the OFF position. The only place I could pull over was the bridge where the shoulder is very narrow. No matter how many times I tried to get the car run, it would start up, run poorly, and die. And while anxiously repeatedly telling my neighbor to not get out of the car, I was also cranking the car. So stressful. But I noticed something. Putting the key in the ON position would automatically progress the wipers one inch. After doing this many times to get wipers back down into resting position, I got the engine to start back up, running just as well as it was before the wiper stalk bump. I drove it forward off the bridge far on the shoulder. I pulled out the fuse. What strange is that all of my turn signals and both headlights worked absolutely 100% perfectly for the rest of the 9 hour trip. My neighbor's theory is that the wipers could have a wire short or bad ground and are trying to use a ground from the other engine components. That one fuse powers both the wipers and horns. Since I already investigated what I think was the entire horn system, that means I need to investigate the wipers.

After such a long read, what are your thoughts?

[CIK7]

I pulled out the fuse. What strange is that all of my turn signals and both headlights worked absolutely 100% perfectly for the rest of the 9 hour trip. My neighbor's theory is that the wipers could have a wire short or bad ground and are trying to use a ground from the other engine components. That one fuse powers both the wipers and horns. Since I already investigated what I think was the entire horn system, that means I need to investigate the wipers.

After such a long read, what are your thoughts?

So yesterday, I set aside my frustrations of possibly being unable to solve this. I took off the cowl, ecu cover, ecu box, and ww reservoir filler neck. I started under the cowl. The wiper motor contacts, wiper wiring, and under-cowl wiring looked good.

But I did find the classic brittle, cracking, corroding wiring on the ww fluid level sensor. See the difference from the one I rebuilt about 4 years ago and installed last night and the one I removed last night. I also taped the ww fluid pump negative wire where a rat had lightly chewed on it. After both tasks, I installed the wiper/horn fuse.

Both the horn and wipers work flawlessly. I activated the hazards, headlights, brakelights which all worked flawlessly. No weird buzzing. Twice today, I went out and test all functions. A little bit ago I started the car, activated all functions and let those and the engine run for 15 minutes while I tossed the ball for my dogs. When I came back everything was still flawless.

Now I have 2 ww fluid level sensors to rebuild.

[abscate]

See if you can find your year wiring diagram and post up the wiper and horn circuit part here so we can chew on it