My heating,blowers,rear demister and external temp reader all go intermittently,I had an auto mechanic look at it and he thinks my HVAC circuit might be gone or on the way out after running diagnostics on it. Has anyone else had this and is it a big and costly job to fix?.. It happens usually after a cold spell and can come back working for 2-5 days without issue so its not a battery or fuse issue.(my wipers went yesterday and I'm not sure if that is related).

Thank,s

ColmOC