97 LHS A/C controls

Has anyone had the issue with the blower motor staying on high speed?
Had this happen the other day, unit was working fine with the fan in
manual mode. Stopped the car for a short errand and started the car and
the blower immediately went into high speed. No change from the speed
control, all the other functions work OK as in switching from vent to
floor to A/C to defrost, etc.
Must be an obvious short to ground somewhere as you can actually push
the "Off" button on the control and it still runs..
Ran the codes today and nothing comes up. The fan will shut off when the
key switch is turned off... any ideas as to where to look next?

 

There's a fan speed controller that mounts in the bottom of the A/C box
(under your glove box) that controls it. Like blower resisters, but much
nore complicated. Mine stuck on high about two weeks ago, then recovered.
While it was stuck, I found that new ones are $450, which is totally
ridiculous, and the junkyards don't have any, because everybody wants them
for the obvious reason. I decided not to fix it, and later it fixed itself.

High fan is much better than no fan with the current weather.

 

The high speed uses a relay inside the blower power module. This is the
module mounted to the HVAC unit near the blower. Rap on it a couple of
times, It'll most likely shut off. You'll need to replace the module.

If you have a late build 97 it may have the 2nd generation LH power module
in it. These were prone to internal shorting caused by water intrusion.