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Hello my name is***** am an ASE Master Technician and I am glad to help you out with your question.
Do you have a wiring diagram of the blower circuit?
Do you have a voltmeter?
The next thing to look at would be the switch or hvac controller.
You may have a wiring problem or a short to power that could cause the melting.
Does it have auto or manual temp control for the ac/heat?
Wiring diagram will help diagnose, I have seen problem with the hvac module and it causes this type of problem. I would verify by checking the power and grounds to the module first.
We have a company at our dealership that rebuilds the EATC modules, we have an exchange program.
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