2013 Sonic LT 1.8L A/C Clutch wont engage

[Poobah47]

Neighbors car, I'm helping...OK, clutch will not engage. 84 degrees right now, I have about 93PSI across the high and low side engine off. No engine lights, I have replaced the pressure transducer and have ordered an evaporator temperature sensor/thermistor. Upon removal the thermistor read about 50 ohms at ambient. I put in freezer and verified it changes, up to about 80 ohms. Don't know what it should be for resistance. I have ordered a replacement, be here on 6/11/21.

As I understand it, the engine light should illuminate if the pressure transducer or the thermistor is defective you would get an engine light.

I have jumped across the clutch relay and the system works as advertised. Nice cold air. Pressures, 35 Low, 190 High. I'm starting to think it's a control module.

Any ideas?

Thanks all.

 

[Decastro45]

Neighbors car, I'm helping...OK, clutch will not engage. 84 degrees right now, I have about 93PSI across the high and low side engine off. No engine lights, I have replaced the pressure transducer and have ordered an evaporator temperature sensor/thermistor. Upon removal the thermistor read about 50 ohms at ambient. I put in freezer and verified it changes, up to about 80 ohms. Don't know what it should be for resistance. I have ordered a replacement, be here on 6/11/21.

As I understand it, the engine light should illuminate if the pressure transducer or the thermistor is defective you would get an engine light.

I have jumped across the clutch relay and the system works as advertised. Nice cold air. Pressures, 35 Low, 190 High. I'm starting to think it's a control module.

Any ideas?

Thanks all.

This happened to my 2014 Sonic last week, problem was coolant temperature sensors, car has 2 one after the thermostat housing and the other in the right bottom part of the radiator, they both looks the same but have different part numbers, if You have a scan tool you’ll find 2 codes one that reads that one sensor performance is incorrect but no check engine light, the one in the cylinder head was the faulty one, I ended up replacing both and I got my AC back.
hope this help you

 

[Poobah47]

This happened to my 2014 Sonic last week, problem was coolant temperature sensors, car has 2 one after the thermostat housing and the other in the right bottom part of the radiator, they both looks the same but have different part numbers, if You have a scan tool you’ll find 2 codes one that reads that one sensor performance is incorrect but no check engine light, the one in the cylinder head was the faulty one, I ended up replacing both and I got my AC back.
hope this help you

Thanks for chiming in!

I investigated and located but my 79 dollar scan tool won’t dig that deep. I’ll look further and report back.

 

[Poobah47]

I ordered and replaced both Temp sensors. The ring around the back of the Thermostat/Inlet housing that holds the clip that holds the sensor broke off, Ordered and installed new housing which came with all the sensors. When removing the throttle body heater hose, the 4.62 plastic 90 degree fitting broke off in the old housing, plastic welded together. Ordered and installed 90 degree hose fitting.

I had tested the thermistor at the evaporator by putting in freezer and putting in sun. Watched the resistance vary, figured it was OK. I had already ordered on but was on a slow boat from China. I installed it anyway just to be sure. It fixed it. A/C working fine.

 

[Decastro45]

Hi, good to know that you were able to fix it, hope that I pointed you in the right path.
I will also like to add in case somebody else find this problem, that there is an aftermarket aluminum thermostat housing (comes complete including thermostat and sensor), I installed it on my car and same as you, plastic hose that goes to the throttle, broke I had to replace it also. 2 years later everything is working fine. I replaced the plastic with aluminum cause I know that the plastic tends to crack cause of the temperature it gets from the coolant.

 

[Elainew]

Hi, good to know that you were able to fix it, hope that I pointed you in the right path.
I will also like to add in case somebody else find this problem, that there is an aftermarket aluminum thermostat housing (comes complete including thermostat and sensor), I installed it on my car and same as you, plastic hose that goes to the throttle, broke I had to replace it also. 2 years later everything is working fine. I replaced the plastic with aluminum cause I know that the plastic tends to crack cause of the temperature it gets from the coolant.

I’m having an ac problem I just got my 3rd ac compressor for this car because they said the clutch was broken on the last two it just got fixed and replaced in a shop and the air is cooler but not cold like it used to be and sometimes gets warmer then cooler again also it’s cooler out of center vents and driver side vent is significantly warmer could this be is this something I could look at next for the problem ?

 

[Decastro45]

Hi, I’m no AC expert, but for trying to help you, first I will suggest to use a scan tool and check the ac module for codes, even if the check engine lamp is off, I‘m suggesting this because a similar problem like your’s happened to my brother in his suv and the problem was a small motor or actuator that open and close the air circulation flaps inside the dash, this is so air goes to the windshield, foot or straight at occupants. It also opened the air recirculating flap.
hope this helps.

 

[Poobah47]

I, too, am no expert but I have fixed a few A/C systems, particularly the Sonic.

The system has a Computer dedicated to HVAC, I think it's called the HVAC Control Module (HCM). It talks to the main (ECM) computer as well.

Those guys provide the logic control to turn on and turn off the compressor.

Inputs to this combined (ECM/HCM) system are a number of temperature and pressure sensors.

There's a pressure transducer at the compressor, a temperature sensor at the evaporator. These are the primary sensors affecting the A/C systems. Other sensors (engine temperature sensors) can also affect operation but not likely to cause your symptoms.

The Evaporator thermistor is a cheap part easy to get to. It's on the kick panel to the right and above the gas pedal. Two wires, little connector with a clip. (Don't break it!) 12 bucks or something. No tools required.

The pressure transducer that monitors the high pressure, I'm pretty sure is at the outlet at the compressor D fitting. It can be changed in 10 minutes by a skilled mechanic. Not expensive items but both need to be giving the proper information to keep the compressor running at the proper intervals.

Good luck.