AC Thermistor Question

Hi,

I have an 87 4runner with a bad thermistor in the AC system. The symptoms are as follows:

The AC compressor clutch will not engage unless I short out (jump) the thermistor connection to the amplifer. I checked the resistance measurements at the disconnected thermistor plug and get an open circuit reading rather than the 1K ohm I expect. If I jump the thermistor, the clutch engages and the system cools nicely.

My question is: I understand the purpose of the thermistor is to cycle the compressor clutch at low temperatures to prevent freezing of the evaporator. If I leave the thermistor shorted out of the system, how likely is it that freezing will occur and will it cause any problems that can't be corrected by just turning off the AC for a few minutes? I live in northern California with relatively low humidity.

Secondly, is there any way to access the thermistor without pulling out the whole evaporator box? I'd like to avoid evacuating the system if I don't have to.

Thanks for any info! Mark

Reply to
ch4
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If you leave the thermistor shorted, I think the likelihood that freezing will occur is fairly high, especially if the receiver drier is the original one. If you watch the normal operation of the AC system, the compressor will cycle on and off. Besides freezing on the evaperator, it is possible that you will get internal freezing. Turning the AC off for a few minutes will alleviate this problem, but it is tough on the system, especially a 20 year old one.

I don't remember offhand how the thermistor is positioned, but I believe you can access the thermistor without having to pull out the evaporator. You may even be able to access is without opening up the evaporator cover.

Reply to
Ray O

A evaporator coil that is to cold may not always ice-up. But your compressor will be history if/when liquid refrigerant gets to it. That seems like a pretty big risk.

hmmm, I bet just 1 screw holds the part in place.

GL Dan

Reply to
Danny G.

Thanks for the advice; you're right the thermistor is accessable without pulling the evaporator. I was able to get to it by just opening the case from the bottom. It's held on to the downwind side of the evaporator by a clip so it's easily removable. I just need to get a replacement and I'm back in business...

Ray O wrote:

Reply to
ch4

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