AC system logic or schematic question (pressure switch and rad fan) - Toyota Yaris Forums

rayfloyd170 · 08-29-2023, 12:54 AM

Hi to YarisWorld friends,

Good day.

I have a 3rd Gen 2016 Yaris Sedan 1.3MT 2NZ-FE

Last 2 weeks ago i topped-up R134a (with respect to ambient) and after that everything went well without any issues. I was checking both LP and HP and both were good within acceptable pressure range.

Yesterday, I was waiting for a phone call inside my Yaris for about 30min of idling with AC full blast. The ambient temp here in Saudi Arabia was around 43-45C or 109-113F and i noticed my coolant temp was rising and eventually going above 96-98C or 205-208F.

I was alarmed because suddenly the AC blower blows warm air and when i checked the rad fan it was not spinning at 98C or 208F. I checked the HP side of the AC system with a manifold and find it to be very high but below the threshold to activate the HP pressure switch ( reference 3.14 MPA of 455psi). I see only around 370psi in discharge, but it could be that my pressure switch is no longer calibrated hence it activated and shutdown the compressor.

But, here is my question.

If the AC compressor HIGH pressure switch is activated, does it also shut down the rad fan when temp is above 98C/208F?

Thats what happened in my case. I adjusted the refrigerant pressure to have a discharge of around 290psi and this immediately brought back the condenser/rad fan to high speed.

Condenser/rad fan motor is ruled out to be defective here since it is working at high speed.

I am not sure if this is the correct logic. Rad fan motor should continue to spin regardless of the pressure switch is activated or not. It should be dependent on the engine or coolant temperature if it reaches the setpoint of 96C/208F above it should cut-in to avoid possible engine overheating.

Please let me know your thoughts and in case there is a valid reference to this subject please share it with me. thanks

08-29-2023, 12:54 AM	#1
rayfloyd170 Drives: Yaris 2016 1.3 Manual Join Date: Jun 2017 Location: SAUDI ARABIA Posts: 125	AC system logic or schematic question (pressure switch and rad fan) Hi to YarisWorld friends, Good day. I have a 3rd Gen 2016 Yaris Sedan 1.3MT 2NZ-FE Last 2 weeks ago i topped-up R134a (with respect to ambient) and after that everything went well without any issues. I was checking both LP and HP and both were good within acceptable pressure range. Yesterday, I was waiting for a phone call inside my Yaris for about 30min of idling with AC full blast. The ambient temp here in Saudi Arabia was around 43-45C or 109-113F and i noticed my coolant temp was rising and eventually going above 96-98C or 205-208F. I was alarmed because suddenly the AC blower blows warm air and when i checked the rad fan it was not spinning at 98C or 208F. I checked the HP side of the AC system with a manifold and find it to be very high but below the threshold to activate the HP pressure switch ( reference 3.14 MPA of 455psi). I see only around 370psi in discharge, but it could be that my pressure switch is no longer calibrated hence it activated and shutdown the compressor. But, here is my question. If the AC compressor HIGH pressure switch is activated, does it also shut down the rad fan when temp is above 98C/208F? Thats what happened in my case. I adjusted the refrigerant pressure to have a discharge of around 290psi and this immediately brought back the condenser/rad fan to high speed. Condenser/rad fan motor is ruled out to be defective here since it is working at high speed. I am not sure if this is the correct logic. Rad fan motor should continue to spin regardless of the pressure switch is activated or not. It should be dependent on the engine or coolant temperature if it reaches the setpoint of 96C/208F above it should cut-in to avoid possible engine overheating. Please let me know your thoughts and in case there is a valid reference to this subject please share it with me. thanks Last edited by rayfloyd170; 08-31-2023 at 06:21 AM.