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86 760T Automatic Climate Control (ACC) Unwanted Heat[740-760/86] posted by Paul Stasko on
Sunday, 3 May 1998, at 3:49 p.m.

Recently with my ACC in the no A/C position, I've gone from normal ventilation to sudden heat. Happens periodically and I have to either shut system off or adjusting temperature knob all the way down may stop heat. I have tested outside air temp sensor and it read about 40 ohms, not sure how to check inside air temp sensor. Or could it be something else? Any ideas? Thanks.

Re: 86 760T Automatic Climate Control (ACC) Unwanted Heat[740-760/86] posted by David Jeff on
Sunday, 3 May 1998, at 5:22 p.m.

I have 3 760s with ACC that sometimes seem to have a mind of their own. By trial and error and desperation; I have learned that the 3-wire connector (labeled "K" green wire, "J" black/white wire and "H" blue/white wire connecting to a green, black and brown wire) located directly behind the glove box has some influence on the ACC.
If connected I get heat. If disconnected, I get air conditioning. I know this is by no means the correct solution; but, it appears to be my most ecomomical choice. If any of you electrical experts could tell me what I can do to return my ACC to its fully "automatic" state, I would be appreciative. --
David Jeff

Re: 86 760T Automatic Climate Control (ACC) Unwanted Heat[740-760/86] posted by Don Willson on
Sunday, 3 May 1998, at 8:01 p.m.

On my '85 740 without automatic climate control I found:
Since the heat is ultimately controlled by a 'fail on' vacuum controlled valve in the heater hose line you might check there. It requres a vacuum to close the valve, thus in the cold climates it would fail and deliver heat. I found that this valve leaked badly and 'fought' the air conditioner. I replaced it with a GM valve that it better built and only costs about $17 rather than the $75 for the Volvo valve. --
Don Willson, Richardson, Texas, 1985 744A with 115k, 1989 765T with 125k.


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