Testing auto HVAC controls.
Thread Starter
Instructor
Joined: Jul 2008
Posts: 233
Likes: 1
From: Acworth GA
Testing auto HVAC controls.
Trying to resurrect a 98 wit 20k. Been sitting for years with various issue. Currently working on a inop HVAC blower. Blower/fan works when connected to power. The control module has constant 12 v and ground, but not getting any signal voltage. I assume that comes from the control panel. Panel lights up and fan displays show different speeds, but doesn’t seem to be putting out the voltage to the module. It there any other test to complete before ordering new controls.
Melting Slicks
Joined: Jul 2004
Posts: 3,294
Likes: 480
From: Brea CA
The operation of the HVAC blower is a bit more complex than the controller powering the fan directly. If you have the dual zone system there is a signal from the HVAC controller to a digital speed controller mounted in the blower housing. If you have the manual single zone system the control panel switches between a set of resistors mounted in the blower housing. The output of either of these connects directly to the blower motor. 99% chance that if everything else checks out the speed controller/resistor assembly have failed.
Also check fuse 49 in the fuse box in the passenger foot well. This is the power to the fan for both controller types. It is a 30A fuse.
Gary
Also check fuse 49 in the fuse box in the passenger foot well. This is the power to the fan for both controller types. It is a 30A fuse.
Gary
