ToreB

I cannot explain any problems or lack of problems you may have had. I guess evap icing depends on the temperature and humidity of the ambient air. cooling technicians may know a lot more of this than I do.

The evap sensor is really not detecting faults, but is involved in normal A/C operation. It measures the evap temperature, and the CCU will shut off the compressor when it reaches 4 deg C. As mentioned above, this is the only mechanism that prevents icing on the evaporator.
Cheers,
Tore

JB 911

I have seen posts where bending or repositioning the final location of the sensor away from the fins makes colder air. I am think who ever did this decided to go one more step and put it in a cold environment (the duct) but away from the fins completely to get colder air in the cabin. I do not believe the harness is that long to reach over to the blower motor. I think he cut the sensor, spliced in some wire, and moved it over there. It's hard to tell from the pics though, I could be off.

In your first post, you don't say the air wasn't working, you just say there was blower whine. I ask only because normally someone would say their air wasn't working. Are you 100% you measure the right pins?



Your compressor may still have been shut down if the temp in that duct got cold enough before the evaporator froze. The symptom of a freezing evaporator is your air starts to blow warm like you have no ac. Then in you shut off the system and turn in on 30 mins later it works fine. Have you ever experienced this in the last 7 years? How would you rate your ac the last 7 years? Do you regularly run the ac in the summer for 20-30 min drives or more or are they shorter?

Here is an interesting diy that may help you also. Scroll down to page 8.

http://www.ozarkpca.org/docs/injectors/2009_03.pdf

gtroth

Yeah, that's very helpful- thanks so much. I'll bet I'm running the evaporator colder than ever before. No signs of freezing this week. I drive it ~40 minutes a day twice a day.

I don't recall the AC ever cutting out and running warm for a while (ie clearly indicating a freeze). But who knows.

You're right- the OP spliced in that white wire you can barely make out in my first pics so the sensor would reach the air vents.

AC was working before and after I fixed the fan squeal, though never super cold like right now. That's why I checked the pressures- thought the air should have been colder.

The original sensor was bent some, so maybe PO tried that trick first.

100% sure I measured the correct pins (resistance at the CCU harness went from infinite to 0 ohms when I connected a jumper across the sensor in the frunk, then to 3.3K when I put the fixed resistor in).

I think I fully understand this now. Well, except is a frozen evaporator risky or just annoying? An academic question at this point since I'm going to put things right...

Thanks again!