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Old 01-04-2007, 02:01 AM   #1
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Default Rear Defrost + Door locks issue?

Being in the cold MN climate during these winter months, I have to use the rear defroster much.

But after a 2-3 mile journey home from work, when turning on the rear defrost as i leave, after about 60-70% of the drive, it wont engage on again. Yes i understand it has to reset, but when i park, my power locks don't respond during this time either.

If i try keyless, i can hear the RAC module trying to fire the locks, but still nothing happens.

Any thoughts?
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Old 01-04-2007, 02:52 AM   #2
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could there be a short on the defroster which draws too much current or overheats something and shut them out? way out of my knowledge but just a guess.
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Old 01-04-2007, 09:01 AM   #3
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my car did it too...... just wait a few minutes and it will all work agian... watch out cause your power seats wont work either.... i would turn it on till it started to defrost then turn it off for a few then turn it on.... just dont let it turn its self off!!!!!
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Old 01-04-2007, 11:26 AM   #4
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When my driver'* door lock didn't work, it was the lock assembly.

But I think this maybe a relay issue. The set behind the glove box.
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Old 01-04-2007, 11:46 AM   #5
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There door locks on the keyless systems are wired in an odd way.. You will have the door lock control relay, which will have a power source that will be hot at all times, The RAC has a wire( Driver Door Lock relay control ), the power actually passes through the Main door lock relay first( under the drivers seat ), the RAC switches the relay and unlocks the drivers door, then it switches again and hit al of the doors with the unlock signal... Strange to me the way it works, but it works well and almost never fails unless the RAC dies...

Jason, has this been a frequent problem? something that just started?

Guys do we know whats on the same circuit as the Defrost?

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Old 01-05-2007, 03:40 AM   #6
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I haven't noticed it before, maybe it happened last winter.

It'* been decently warm for winter, so not much rear defroster use till a month ago.
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Old 01-05-2007, 06:54 AM   #7
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Quote:
Originally Posted by jr's3800
Guys do we know whats on the same circuit as the Defrost?
Rear window defrost is normally on a dedicated ckt. and not shared with anything else.
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Old 01-05-2007, 08:03 AM   #8
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Quote:
Originally Posted by jr's3800
Guys do we know whats on the same circuit as the Defrost?
If I were in Florida...I could pull the correct year manual off the shelf and check. Off the top of my head...I'd agree with Mark.
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Old 01-20-2007, 01:19 AM   #9
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I am having the same problems.... If I start the car, hit the rear defrost, 90% of the time door locks and power seats will not work. If I shut off the Rear Defrost, within minutes I have power again. Is this a possible overheating of a circuit breaker or a common relay within the rear defrost. Even though the button shows that the rear defrost is on, it is NOT functioning. ZERO power to the rear window. Any help would be great!!
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Old 01-20-2007, 10:52 AM   #10
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Default Problems with defrost and locks

You might check the ground connectors along the driver'* side and passenger side or passenger side. Other posters have shown these.

It could be the defroster causing corrosion problem on the ground buss bars losing ground.

On a 98 H-body I currently have a defroster that affects the radio antenna that uses the grid for signal. It probably is grounds at the antenna box in C pillar but could be elsewhere. I turn on the rear defrost and good radio signal returns.

I had a problem with 93 H-body occasionally losing control of the manual air conditioning control and the unit went into defrost and AC was turned on. At the same time automatic door locks didn't work.
After some time both would work again.

I figured out it was grounds but I had traded the car before following up. I rarely used the rear window defroster so it might have had symptoms but I never connected them.
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