Rear Defroster coming on by itself......what gives ?

[guitarspaz]

Frequently, when I engage the lo/interval speed of the rear wiper, it turns on my rear defrost when the wiper arm comes back to rest. Won't turn off at tha point either without restarting the car, or waiting for a subsequent swipe to turn it off. I tried replacing the rear defrost relay for kicks. No help. Dealer says it's some peculiar wiring problem that they'll have to tear into the wiring harness to find. Not looking forward to the additional rattles that'll be generated from pulling interior panels, dash, etc. Any chance that ANYONE has had a similar problem and can maybe point me in a direction for starters ? I suspect there's a connector with a pushed pin somewhere between the relay panel and the rear...maybe a less than perfect return/ground connection...but who knows. Any ideas ?Thanks.CRG

[rlfreese]

that is weird. the wipers should nt have anything to do with the defrost. I will look tomorrow and see waht I can dig up on the wiring schematic for the car. I have to replace my 2005 vibes front left wheel bearing so I will have time to do this while i am in the garage tomorrow.

[guitarspaz]

Thanks man !!. Definitely strange. They do share the same harness to the back though I suspect, as well as the same disconnect contact block for the rear glass. My theory is that the defrost button sends a momentary pulse etc to something to toggle the state of the relay. I'm suspecting that I'm getting something that looks like that pulse back through the wiring when the wiper motor runs at the rear. Only does it when in interval/slow mode, or when I kick the rear washer motor. That will toggle it as well. I'd be very interested to know what the defrost button really does. The relay only had 4 contacts...I'm assuming 2 for teh coil and 2 for the contact. If so, is there an intermediate controiller somewhere that the button feeds ? Please let me know what you find, and thanks much for taking the time. Where did you get your schematic and how much ?

[joatmon]

I remembered another thread by someone who had the same problem, and looked around, finally found http://forums.genvibe.com/zerothread?id=20138 and came back here to suggest you contact that other person who had the same problem when I realized it was you. So here I thought I might be able to help hook you up with someone else who had the same problem, but alas, no.Before they tear apart the wiring, I suggest they try replacing the rear defroster switch. It has the solid state timer stuff in there, and gets it's control power from the rear wiper power source, maybe the wipers are putting a spike on that power line and the weak defrost switch gets confused by it. or maybe not, don't really know, but replacing a switch for a quick test is easier that tracing wires throught the body of the car.

Attached files 025rww.pdf (30.7 KB) 

[rlfreese]

I found a Wire diagram for the vibe wipers. Still doing some research. it was raining today and the garage was otherwise ocupied so i couldnt pull the panel off the hatch. I will try tomorrow when it is sunny.http://www.raintracker.com/Com...3.pdf

[guitarspaz]

Thanks much. I'll try the switch first. You don't happen to know the pinouts for it do you ? Was thinking of trying a capacitor across the power termonals as an experiment.Thanks again.

[joatmon]

Quote, originally posted by guitarspaz » I'll try the switch first. You don't happen to know the pinouts for it do you ? Was thinking of trying a capacitor across the power terminals as an experiment.I attached the wiperr schematic above, here is the defroster schematic

Attached files 044rwd.pdf (28.7 KB) 

[rlfreese]

looks to me like it most likley is the switch. I cant see anything else but a relay that might couse this but that isnt realy happening either. So Yes I would try replacing the switch.

[guitarspaz]

The switch took care of it !!, and the dealer reimbursed. Many thanks to all !!! now...the only thing left is that annoying sunroof shade rattle......