Speedtoys

Trip to tahoe last weekend...fearful...was a wintery _mess_...but..

I can control the temp at the floor, and doors it seems, but the center vent is always quite cold..i mean, very much not the desired temp, unless I set the temp to full hot...then the center vent seems to react.

I have had the temp control stepper motor out, it works fine. I have seen it work, and have tested the external temp sensor, and replaced the internal one as well.

Mrmerlin

you need to run a check on the vacuum pods ,
remove the left console cover and use the myti vac to see what ones are leaking
If you need more guidance then look up Wally Ps HVAC guide at 928GT.com

Speedtoys

They've all been replaced.

Did this work last August when it was all apart. The system holds vacuum.

Mrmerlin

OK, then take the HVAC head out ,
open it and clean the wiper grid,
as an alternative just spray some contact cleaner into the grid,
thou this can wash the fluid into parts that might not need it..

I have found that dirt can get into one or more of the fingers on the grid,
and create a situation where certain parts of the system stop working

dr bob

Jeff --

Set the manual flap slider in the center vent to mid position. This blocks cold airflow from the evaporator box. A causes a lesser flow of only air that has passed through the heater box. Primary cabin heating is typically via the floor vents plus the vents on the armrests. In winter, the system supports fresh air flow through the top of the center vent so your toes can be toasty without blowing hot air in your face. That's a feature that most 'murikan cars are missing. Cool (blended) fresh air for breathing lets me stay awake while driving with the heat on, while allowing full heating at the floor level. That hot air rises into the cabin.

Speedtoys

Dr:

I think ive noticed that, but I think I mostly have to close the center vent entirely.

I find air from the center vent helps defrost the rear window easier too.

Merlin:

The guts of the head were cleaned out ~yrs ago..put in a new bulb, sliders, etc.

Mrmerlin

UMM OK but still it only takes a small piece of dirt to get caught in the finger slider then it will be disabled,
take a bright flashlight and look into the HVAC head openings