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Adjusting Evaporator Core Temperature


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#1 Maxzillian

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Posted 02 October 2018 - 01:09 PM

This is just a tech-tip for anyone needing to make this adjustment.

Some of you may have noticed that on top of the HVAC control module there is a label placed over a hole, "H-C". Beneath this hole is a small potentiometer that can be adjusted using a flat bladed screw driver. I've seen in the past that people have wondered what this pot does and it is not covered in the service manual (at least the 88-89 copy).

I have managed to confirm that this controls what evaporator core temperature the HVAC cycles the compressor at. With the factory setting, my car had a duct temp of approximately 45-50F and I was able to turn the pot a small margin and get the temps down closer to 40-45F. Now this does expose me to the risk of freezing the core over on long drives, but I'll take that for the small improvement in AC performance in every day driving.

With the potentiometer maxed out I recorded a duct temp of about 55-60F.
What's the fun in making something simple?

'87 TSI - StarOrion braided brake lines, StarOrion radiator, StarOrion alternator, StarOrion 2.5" stainless exhaust w/Magnaflow muffler, 1G MAS, Competition Clutch 15 lb flywheel, Competition Clutch Stage 4 clutch, Mookeh polyurethane bushings, ABS elimination, 8:1 Wiseco Pistons, TD05 14G turbocharger, Axiss ceramic rear brake pages, Hawk HP+ front pads, heat wrapped and ported exhaust manifold/turbine housing, Accusump oil accumulator, remote oil filter, NJV head, EVO intercooler, remote battery, D2 coil over struts, flatty front struts and control arms, 8" non-SHP wheels all four corners, 12.75"x1.25" front rotors with 4 pot Wilwood calipers, manual brakes using dual master cylinders and balance bar, gutted (deleted) brake proportioning valve and modified steering pump speed sensitive valve.





#2 87redcat

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Posted 02 October 2018 - 03:34 PM

Good info. This should be pinned.
I got blisters on my fingers!!!

#3 pcristquester

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Posted 02 October 2018 - 05:08 PM

Finally, THANK YOU!
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