Heat Less in the Carolinas

[Phil Rose]

At 5:18 AM -0500 12/4/05, TooManyAudis at aol.com wrote:
>In a message dated 12/3/2005 11:01:30 P.M. Eastern Standard Time,
>kneale at coslink.net writes:
>  Several years ago, I  experienced the heat dropping
>off to cold air blowing out after 20-30  minutes of driving.  If I bumped
>the requested temp up a couple  degrees, it would heat more briefly before
>going cool again.  I fixed  that by replacing the temperature regulating
>flap motor.  See Chris  Miller's website for  directions:
>http://members.aol.com/c1j1miller/climate.html#Temperature%20regulating%20fl
>ap   If you scroll down, there are pictures of the cover for the  flap
>motor and of the flap motor itself.
>
>I believe that's what I was looking for.  Bernie chastised me earlier  for
>not providing enough information or running through some diagnostics before 
>posting -- Between you and me, does this guy have a job, or is his job 
>responding to posts at a moment's notice with something to make the 
>rest of us  feel
>like fools?

Ah Bernie just can't help himself. ;-)

>   I have not yet torn  into the car to
>verify -- May just do that after the Giants beat up on  Cowboys on Sunday.

It's easy to diagnose if there's temperature flap-motor 
(potentiometer) malfunction: Simply drive the car until the engine is 
warmed up; then compare the readings on two CC diagnostic channels 
(channels 8 and 9, as I recall). One channel shows the flap position 
(coded value) that's being requested by the controller based on the 
temp setting you've chosen, whereas the other channel tells the 
actual position (coded value) of the flap. If they don't consistently 
agree (should be the same--within a few units--after a short time), 
you can assume there's a problem with the potentiometer (dirty, worn, 
etc). A bad potentiometer can cause the channel output to swing 
wildly to an extreme value--it likely will indicate a shut position 
when you can't get any heat. The Bentley manual describes this in 
more detail.

The potentiometer component could, in principle, be cleaned or 
replaced, but I'd advise to replace the entire flap-motor assembly 
and be done with it for the foreseeable future.

Phil
-- 

Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net