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Old 11-23-2004, 03:03 AM
akm akm is offline
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98 GMC AC controls/relay

my dad's truck is a 1998 GMC 2500 5.7.
for some reason the AC/heater will not turn off and continues to blow on to the floor only.
when "whatever" went wrong with it, now we hear some relay clicking in the dash.
i guess i could just find it, pull it and get another one, but i'm not sure what its called, and really not sure if that is even the problem.

if someone could give me a heads up on what it might be or what to look for, that would be great.

thanks in advance

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Old 11-28-2004, 01:53 PM
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Not sure about the newer models such as a 98, but in the 80s a lot of the heater/AC controls were vacuum assisted. Are you sure that a vacuum line is not off?

Just guessing, maybe someone else knows more.....
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Old 11-28-2004, 02:12 PM
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AKM

I have a 98 2500 also and my climate controls act a little wierd. The fan switch has some kind of short in it. Sometimes it wont shut off the system and the a/c compressor will run with no fan. It will also not switch the incoming air to the default floor vent it will stay on whatever the selector is on. When it was new it wouldnt do that. If i turn the fan switch back and forth it will sometimes work like it is supposed to. So my guess is that yours has some sort of problem with the climate controls(the three knobs in the dash) like mine just a little more serious. People have bound to have crashed some of these by now maybe try one from the junkyard? Keep in mind that a friend of mine's tahoe does the same thing as mine though so it might be a common problem.

John
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Old 11-28-2004, 09:26 PM
akm akm is offline
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Quote:
Originally posted by poncho62
Not sure about the newer models such as a 98, but in the 80s a lot of the heater/AC controls were vacuum assisted. Are you sure that a vacuum line is not off?

Just guessing, maybe someone else knows more.....
i'm pretty sure that this is not vacuum controlled, but i've been wrong before and i'll check it out.

thanks

Quote:
Originally posted by propaniac
AKM

I have a 98 2500 also and my climate controls act a little wierd. The fan switch has some kind of short in it. Sometimes it wont shut off the system and the a/c compressor will run with no fan. It will also not switch the incoming air to the default floor vent it will stay on whatever the selector is on. When it was new it wouldnt do that. If i turn the fan switch back and forth it will sometimes work like it is supposed to. So my guess is that yours has some sort of problem with the climate controls(the three knobs in the dash) like mine just a little more serious. People have bound to have crashed some of these by now maybe try one from the junkyard? Keep in mind that a friend of mine's tahoe does the same thing as mine though so it might be a common problem.

John
yeah i figured this was a common problem.
these trucks seem to have many common problems such as they all seem to burn up the tail light sockets/ board (whatever you call it), the electrical do hicky that controls the wipers located on the front of the fire wall, fuel pumps, power steering pump lines, window regulators, the door handles are made out of pot metal and like to brake off inside and out, the front brake lines get old and make it pull when stopping and probably several other things that i can't remember right now.
i used to work on SBC telephone trucks and 9 times out of ten, these were the main problems with the trucks.
i've probably ran into this problem before or seen it before but just can't remember, so maybe i'll call up my old boss and ask about it.

thanks for your input.

Last edited by akm; 11-28-2004 at 09:26 PM.
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Old 11-28-2004, 09:27 PM
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Unfortunately they are not vacuum operated. There are little electric actuators that control the doors and direct where the air goes.

Maybe someone else has some Ideas.

John
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