Need help w/ Auto Heat System

[SK]

My friend has an '85 with the auto heat system. He is having heat problems (no heat) and does not know how to trace the problem. He disconnected the push rod from the heat servo (under the parking brake housing) and the heat boxes at the exchanger will open and close manually, so this is not the problem. It must be the servo that opens and closes the heat boxes, the circuit board in the parking brake housing, or the temp sensor.

Do any of you know how to go about testing which item is not working w/o just replacing? I don't because my '85 is manual heat.

Do temp sensor go bad? I would think that part is cheap.

have any of you experienced similar problems?

Thanks in advance.

[911Seattle]

Just had the same problem. I ended up taking everything apart and checking all the electrical specs within the dial set-up between the seats.....was stumped because everything checked out. I then checked the two blowers under the front dash area by hooking up a direct power source....they worked fine. At that point I sent into the shop.

The final answer to my problem was that the main blower in the engine compartment went bad. Can't explain the electrical reason, however, if that blower is out...the whole system won't work (as told to me by my mechanic). So give that a try.

Good Luck
Jesse

[schulr]

This is one of the better articles on heating systems, my bet is either the engine compartment relay is out or the blower itself.

http://www.type-911.co.uk/images/exhausts/

go to this link and scrol down to the below files

heatingtech1.jpg 28-May-2002 14:42 306k
heatingtech2.jpg 28-May-2002 14:42 317k
heatingtech3.jpg 28-May-2002 14:43 288k
heatingtech4.jpg 28-May-2002 14:43 352k
heatingtech5.jpg 28-May-2002 14:43 224k
heatingtech6.jpg 28-May-2002 14:43 132k

Bob