Insane Wipers Topic is solved

xarlock667 · Post by **xarlock667** » 20 Jul 2017, 11:48

Hello all. I have a major problem with an XC90, 2005 AWD T5. The wipers act on their own, without any regard for the controlls. They turn on, they run a few seconds, they turn off. They stop in random positions, they run for random times, usually less than 45 seconds, then they just quit totally for up to 2 minutes. You cannot turn them on, you cannot turn them off.

I have swapped all the relays, I have swapped all the fuses, I have pulled the CEM, and I found corrosion on it, so I cleaned it and it did the same thing. I swapped the CEM with the CEM from another newer XC90 just long enough to see if it would keep doing it, it did. I have put the wiper assembly in the newer XC90 and it worked perfectly. I pulled the switch from one and put it in the other, and again, no joy.

The power is coming through the BLUE wire into the motor.

SO, it is not the CEM, it is not the Wiper Motor Assembly, it is not the Switch, it is not the Relays or the Fuses. I am open to suggestions.

xarlock667 · Post by **xarlock667** » 21 Jul 2017, 08:38

Bump! I still need help!

Post by **matthew1** » 21 Jul 2017, 09:39

Posted to MVS Facebook page.

The paradox about posts done right -- detailed explanation of the problem and fixes tried -- is that it discourages reply posts because "he's already tried that".

If the FB post doesn't get this responses, get back to me and I'll try other methods.

This is a "textbook", perfect post. I'm sorry I can't help directly.

shegarty · Post by **shegarty** » 21 Jul 2017, 10:39

Sounds like it could be a bad/corroded ground connection. Try tracing the ground from the motor to the chassis. Or you could try running a new ground from the motor to a known good connection, I'd be inclined to try this first and see if it helps.

Post by **mrbrian200** » 21 Jul 2017, 14:24

Unplug the relays for the headlamp wipers/washers/high pressure washer depending on what is equipped on your vehicle. It's all tied together in such a way it appears a malfunction or short in any one relay ends up sending power to the windscreen wiper motor on the blue wire. I think it's meant to be a failsafe (a relay failure defaults wipers to 'on' rather than not work at all).
The 'failsafe' behavior is technically a theory, but it looks to me that's what they were trying to do using double throw relays everywhere with multiple power feed points and complexity than basic functionality with isolated circuits would dictate.

xarlock667 · Post by **xarlock667** » 21 Jul 2017, 15:28

FINALLY!!! There is a set of wires under the OVERHEAD CONSOLE. One had been pinched almost in half and it was causing a short circuit! I cut and spliced the wire, packed everything as neatly as I could, and then I tested it... VICTORY!!! NO CEM, NO WIPER MODULE, NOT A FUSE AND NOT A RELAY!!! a stupid damned pinched wire!

THANKS TO EVERYONE FOR YOUR HELP!!!

Post by **mrbrian200** » 23 Jul 2017, 18:38

Interesting. The overhead console/UEM on my sis' MY03 XC90 didn't look like was sitting quite right when she bought it. When I investigated I found the wire harness to the UEM wasn't routed quite right and was pinched between the UEM and the body of the car right at one of the bolts, I think on the left side. She has the rain sensor--it might have been the harness that runs between the two but I don't recall for certain.

I doubt it came from the factory like that-- hers has the dealer installed DVD player for the rear seat passengers either a dealer tech didn't get it back together right (they tap into power at the UEM I believe), or somebody didn't realize those bolts aren't how you get into that thing to replace a bulb and pinched the harness while bolting it back in.