A/C Not Kicking In - Frost Detection Sensor
Have had my 2012 Giulietta for about 20 months now. I love it. The first problem I've had with it just started recently. The aircon wasn't kicking on as it should. I had it regassed last year at the dealer and thought they must not have found a leak when compression testing it. Unfortunately, it's something different.
I now take my car to an independent garage because there is no Alfa dealer in town and the Fiat dealer in town is not much of a winner. I trust my mechanic, but he specializes in Mercedes (our other car is a Merc) and he doesn't have a ton of Alfa experience. I brought the car into him and he found that the gas level was good, but the compressor was not kicking on because a temperature sensor that he called the frost detection sensor was preventing the compressor from kicking on. He says the sensor is soldered in and, the best he can tell, Alfa only sells the sensor as part of a costly loom that would require the entire dash to be removed to replace. He's waiting on Alfa to get back to him if that's true but cleaned the sensor and it functions most of the time now. The other sensors for the dual-zone climate control function as expected.
The sensor is to the left of the driver's footwell (I'm in the UK, so that's the center tunnel) somewhere near the cabin air filter. It was reading -5 degrees and needs to read at least 5 degrees for the compressor to kick in. After cleaning it the sensor reads about 10 degrees even in ambient temperatures above 20. Obviously needs replacing. He's happy to replace it with whatever compatible part we find. We both prefer the OEM option if possible, but anything that prevents removing the whole dash is going to be the winner.
Does anybody know what part he is referring to, if it has a part number separate from the loom, or, if it doesn't, what would be a compatible replacement? Mechanically inclined, but not a mechanic myself, so will dig around and take pics or something if you can point me in the right direction. I have a multimeter and can provide readings if necessary. Thanks.