Rear window wiper/ defroster not working. on 2003 GMC Envoy

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My 2003 envoy's rear window wipers are not working. The problem began when the windshield wipers would stop working every time I would use the spray. I now have noticed that my defroster isn't working either.
I was wondering what may have caused this and what may work to fix them. Any suggestions?
(2) Answers
(1) Comments
A faulty ground circuit in the lift gate of your 2003 GMC Envoy could be causing your problems. The lift gate electrical systems in the lift gate must be properly diagnosed to confirm the ground fault or locate whatever other issue is causing your problems. It is not uncommon to have wiring issues at or near the rubber conduit where the wires pass from the body to the lift gate.
Do you know where the ground connection is in the gate (does wipers and defogger use the same ground) my defogger doesn't work but the wiper does. I do have 12 volts at defogger but still doesn't work.
I only have this problem from time to time, sometimes it works and sometimes is does not. I drive my 2003 Envoy today and had no wipers or rear defogger, got to work and turned on and off power with key and after a couple turns started working again. can anyone explain this, I would like to fix but not sure where I should look since works but not always. could this be also a grounding issue??
Thanks. mike