When i turn on the heater blower to defrost my windshield, and turn on the rear window defroster, the blower sounds like it cuts out, but turn the rear derfroster off and the blower is back to normal air movement- anyone else have that experience- any guesses why that would happen. Thanks

 

Best bet is to get a factory service manual and check the schematics to see how the circuits interact. My first guess is a bad ground.