A/C Not Kicking In - Frost Detection Sensor - Alfa Romeo Forum
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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.
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(Post Link) post #2 of 9 Old 6 Days Ago
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I have the same issue on my 2014 Sportiva. Had the system gassed and tested but it was ok. Then it works every other time I drive the car -- drives me mad. If you have any chance pointing out the position of this sensor with a picture I can clean it out and test it/look for a replacement and ofcourse provide some feedback to you.
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I don't know if I've suffered a similar issue, at the start of this summer I thought my car might need a re-gas but after about 2 weeks of not doing anything my aircon has worked really well for about the last month. I'll have to connect the laptop to the car and see if there are any errors that may point to this "frost sensor". Might even be something like a blocked condensate drain? In which case the evaporator coil may be frozen over causing the sensor to actually be frozen. Anyone know any better?
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What’s the pollen filter condition as a blocked one with poor airflow will also cause freezing
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Quote:
Originally Posted by johnnyroper View Post
Whatís the pollen filter condition as a blocked one with poor airflow will also cause freezing
Without hijacking his topic, I took out the filter and left the filterhouse open for a while -- no problems. Then left the filter out and closed the filterhouse -- problems started again. The search continues
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What you need to verify somehow is if the evap temp sensor is actually reading correctly and evap is icing or if it’s rogue readings.

If it’s doing it’s job and evap is icing then you will be looking at air flow problem over evap or the TEV is not functioning correctly in my opinion.
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What sort of TEV does Alfa fit to the G? The mechanical versions are usually very reliable so unless its an electronic version I'd be surprised if it was the TEV. Thinking more like a clogged evaporator, strange how it works okay with the housing opened?
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No idea on the G but my 159 had mechanical one so would expect the G to be the same.

The pollen filter cover being open has allowed more air flow over evap to keep temp up.
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Quote:
Originally Posted by johnnyroper View Post
What you need to verify somehow is if the evap temp sensor is actually reading correctly and evap is icing or if itís rogue readings.

If itís doing itís job and evap is icing then you will be looking at air flow problem over evap or the TEV is not functioning correctly in my opinion.
I will look into this, I have ordered a new filter to start with. Next step is using MES to check these readings. That is currently handicaped by bloody MES failing to connect with the yellow cable. Need to sort that out first... already went the long way with drivers and settings, I can scan with the ELM connected but when I use the colored adapters it won't connect anymore
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