My HVAC unit started making a terrible buzzing sound and vibrating today when in the off position. Upon taking the cover off, I discovered this relay vibrating frantically back and forth. If I move the selector to any other position the relay works properly and does not buzz. Has anyone else experienced this problem?

 

There is a fix with a relay from radioshak. The relay in question is known to do this. There is a write-up somewhere with instructions. I have not had to do this yet, however have bought the relays (awhile ago)

 

https://rennlist.com/forums/928/6788...re-w-pics.html

 

I had a similar issue where it would buzz. It turned out to be a bad connection in one of the 5 or 6 pin ( been 4 years since) molex plugs that comprise part of the HVAC wiring harness under the center console.

The black power wire got too hot and burned the contact along with the plastic making the connection intermittent. I cut the wire and connected it with a spade connector and have had no issues since.

 

I was able to swap the unit out of my father's '82 into my car and vice versa. With my unit in my fathers car the relay also buzzed when in the off position, swapping my fathers unit into my car did not cause any buzzing. In addition the wiring harness in both cars are in excellent condition. It's definitely the relay inside of my unit as it exhibited the same symptoms in both cars.

 

An update, I sent the unit to 928 International for a rebuild, the relay buzzing is gone now. Apparently the relay was at fault.

 

Are 84 and 86 hvac controls interchangeable?