Cooler Heat with Compressor Running Settings

[Tiggie]

Drove the 90 tonight for the first fairly long trip in cold weather since I "fixed" the A/C.

In settings where the compressor runs (aka anything but floor/vent/off), the heat is cooler, lukewarm is a good estimate.

Change the setting to floor or vent, and it warms up substantially and fogs the windows in short order.

No antifreeze smell ever.

I suspect the evaporator is freezing. Thoughts?

[friskyfrankie]

Is the A/C cold? If the evaporator is freezing that may be low refrigerant.

[Tiggie]

The A/C was cold this summer. It's fairly cold outside so it pretty much blows ice cubes on the A/C setting at this point.

When I charged it, I stopped short of a full charge to see if it held pressure. So it seems likely the evaporator is freezing up.

I just found it strange that it was so cold that the heater core couldn't heat it, or maybe the air flow was blocked with ice.

[friskyfrankie]

Could it be that in other positions like "defroster" the doors are not closing off fully to allow full heat and you are partially pulling in cold air to dilute the heat?

[gadget73]

Its supposed to cycle off the low pressure switch. There isn't any sort of timer or any elaborate control. The idea is that between low outside temps and low airflow through the mostly-shut blend door it will pulse the compressor once in a while and the evaporator will be cold enough to suck some moisture out.

If the compressor just stays on, the switch is probably f'd. I've had problems with these failing the other way, never closing so the compressor runs, but either way the switches just don't seem amazing on these. Oddly enough the OE Motorshaft are the ones I've had the most issue with. Had 2 NOS not work right out of the box. The no-name ones from the parts store that went on for replacements have all been just fine.

[Tiggie]

The compressor does cycle but may not be running the correct amount.
I unplugged the compressor to verify and everything is toasty without the compressor working.
I guess I'll throw the gauges on there and see what it's up to. Never had to use them in December before.

[gadget73]

also makes me wonder how good your blend door seal is. Shouldn't be enough air flow through that thing when set to full hot for the evaporator temp to really matter.