Symptoms of a Bad or Failing AC Thermistor

An AC thermistor is a type of temperature sensor that is commonly found on modern AC systems. They detect temperatures and send a resistance signal to the AC control module so that the automatic adjustments can be made to keep the cabin at the correct temperature. As they are basically ambient temperature sensors, they can be found both inside the cabin and underneath the hood of a vehicle.

AC thermistors read and interpret data on temperature that is critical to the proper operation of a computer controlled AC system, such as those found on most modern vehicles. When the thermistors fail or begin to have problems, they can negatively affect the performance of the entire system and should be inspected. Usually, when an AC thermistor has failed, they will produce a few symptoms that can alert the driver that there is a problem.

Limited cooling

One of the first signs that an AC thermistor may be having a problem is that the AC will only blow cold air for a limited amount of time. If an AC thermistor is not operating properly, it cannot alert the computer of the cabin temperature. Therefore, the module will not be able to activate or deactivate the AC so that the correct temperature can be achieved. This may cause the AC to blow cold air in short bursts, or only for a limited amount of time.

The blower will not function properly

Another symptom of issues with a thermistor will be problems with the blower. Some blower motors use the signal from the thermistor to control their operation. If a thermistor is giving improper, weak, or inconsistent signal, then the blower motor operation may be weak, erratic, or may not function at all. As the blower is what blows the air from the vents, any problems with the blower, caused by the thermistor or not, will greatly affect the AC system’s ability to cool the cabin.

Because AC thermistors can play such a critical role in the proper operation of an AC system, if you suspect that you may have a problem with it, have the AC system diagnosed by a professional technician, such as one from YourMechanic. If needed, they will be able to replace the AC thermistor and restore full functionality and operation to your AC system.


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Ben

41 years of experience
1410 reviews
Ben
41 years of experience
Volkswagen Beetle L5-2.5L - Heating AC - Houston, Texas
i am well satisfied with Mr Smith working on my car(s). He replaced the Jaguar fuel pump like an expert, and then he diagnosed the VW bug ac compressor and fixed it on the spot. I would recommend him to anyone with a car issue
Nissan Altima - Heating AC - Houston, Texas
Incredibly nice and took the time to show me the problem, including comparison pictures between my unit and what a new unit should look like.

Peter

43 years of experience
1321 reviews
Peter
43 years of experience
Saab 9-3 L4-2.0L Turbo - Heating AC - Phoenix, Arizona
He knows what he's doing. Very polite and explained everything. I would no doubt use him again. I highly recommend him.
Mazda Miata - Heating AC - Peoria, Arizona
We are so thrilled to have found Peter as our new mechanic. He is very thorough and knowledgeable. He is also friendly, professional, and extremely honest. He explained to us exactly what services were needed on our vehicle to repair the air conditioner and provided us with an written estimate of the cost. He literally saved us thousands of dollars in repair costs. A local major competitor quoted us a repair cost of a minimum of $1,400 and said that the cost would go up to $2,400 if they discovered an additional part was required. Peter charged us only $202, plus performed the work at our home. The air conditioner in our 2004 Mazda Miata has honestly never worked so great--it always blew out warm air. We just assumed it was how that particular car was manufactured. We would highly recommend Peter to anyone who is in need of an experienced and honest mechanic.

Pedro

31 years of experience
78 reviews
Pedro
31 years of experience
Chrysler PT Cruiser L4-2.4L - Heating AC - Portage, Indiana
Pedro was wonderful! He was early first and foremost. He was very professional and he explained things to me. He worked quickly and was very thorough. Very happy with his service.

Manuel

32 years of experience
580 reviews
Manuel
32 years of experience
Ford Taurus V6-3.0L - Heating AC - Long Beach, California
Good guy. Knows his stuff. Knowledgeable and straightforward with diagnostics and repair costs. I’d love to work with him again! Thank you Manuel!

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