'01 2500HD Heater won't quit

Scott,
I have the same truck and a similair problem. On a cool, but not cold
day, I must set the temp control to "one click" above cold or I get too
much heat. My problem is not bad enough yet to take it in for warranty
work. I would like to hear the solution for your problem. My guess is
that there is a problem in the valve that controls coolant flow to the
heater core in the cab.

Both the heater control panels and blend door actuators have been
causing problems in the new series, the most common fix is the control
head. Based upon certain componts functioning in another truck doesn't
wash with your scenario. Either the control head is not working
properly (any of these Techs know how to operate a Dvom) or the blend
door actuator is at fault (unlikely, since it is responding). Locate a
good diagnostic Tech as I cannot see it from here.

Bush

(in message <
A new heater/ac control head (fan speed control switch, cold/hot variable
selector knob, and the vent selector knob) was purchased along with the door
actuator. The door actuator would move/work, but not when the control knob
was turned. It did cycle to the left, I think, at start-up an remain there
no matter what position the control knob was in.

With two new parts, the next step was to trace the wiring from the control
knob to the actuator. The wires traced out ok during the conductivity test,
but the two power leads were intermittent when the voltage was checked. One
time the lead was tested it was hot, the next time it did not have a voltage
on it. Therefore, the tech believes there must be a relay somewhere
effecting the voltage. The next step was to swap out components from another
truck. My components worked in the other truck, but the other truck's
components did not work in my truck. I hope this additional information is
helpful.

Johnnie

(in message <20030108090052.02326.00000@mb-mu.aol.com
I have a '99 Silverado and I am experiencing the same problem. The heater
control panel and the actuator, that operates the heater/ac door, have both
been tested on another truck and work properly. The mechanic has traced the
wiring between the control panel and the actuator. He believes a relay must
be in line and is the cause of the problem, but has not traced the wiring
under the dash at this time.

I am also looking for a solution to this problem. Thanks for the help.
Johnnie

(in message <20030108090052.02326.00000@mb-mu.aol.com
I have a '99 Silverado and I am experiencing the same problem. The heater
control panel and the actuator, that operates the heater/ac door, have both
been tested on another truck and work properly. The mechanic has traced the
wiring between the control panel and the actuator. He believes a relay must
be in line and is the cause of the problem, but has not traced the wiring
under the dash at this time.

I am also looking for a solution to this problem.
Thanks for the help,
Johnnie

This is an interesting thread. I've been wondering if I've been imagining
temperature differences in my '02 2500HD or what!!! It takes a quite some
time to generate enough heat to warm you up on the latest 8 degree mornings
and then I turn the temp down close to cold and it gets comfy. Turn it off
and back on to go somewhere else and it appears to give you more control
over the temps. Maybe there is a long running issue with these units??? I
know the heater doesn't seem to do the job my '99 Suburban's does
Well, not all the time anyway! :-)

Kevin

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