AC Controller problems

Phil Rose pjrose at
Fri Jan 10 11:05:14 EST 2003

At 8:15 AM -0500 1/10/03, Kneale Brownson wrote:

An interesting read! Scott M's Web page contains (among other useful
things) the following statement:

>According to my GM contact, GM had a service bulletin that
>recommended soldering a 680K ohm resistor across two legs
>(connections) on this position sensing potentiometer. This 680K
>resistor will ensure there is a voltage difference at the input to
>the op amp/comparator if this pot goes open circuit which will get
>the motor turning until the pot wiper contact is reestablished.
>Here is a diagram showing where the resistor should be soldered on.
>A little contact cleaning spray on the insides of the pot could also
>help clean up the pot wiper as well. My A/C system temp control
>finally worked as expected in the 1986 5000T for several years after
>installing the motor and this resistor mod.
>The later 200T/Q servo which is mounted on the air box under the
>plenum cover, may suffer from this same problem, but I have not yet
>had the servo apart on these later systems.

Note Scott's final paragraph. I wonder if the 680Kohm resistor is
what we (who are suffering the "feedback potentiometer syndrome")
should be installing--if/when we pull apart that servo motor assembly?



Phil Rose				Rochester, NY USA
'91 200q	(135 Kmiles, Lago blue)
'91 200q   (58 Kmiles, Tornado red)
	mailto:pjrose at

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