Poor connections. Replace the heater switch with one of these and I've done both in less than 2 weeks. These things can't handle the power they advertise. I was expecting at least one to be defective because they are so cheap, but they were both defective. The switch itself melted and broke the connection. I replaced the module with one of these and they were identical and they said they could handle it but my original lasted a few years while again they only lasted a few weeks. I don't know why but not a quality product.
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