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Ac Temperature Issue

MightyV35
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MightyV35 Contributor

MightyV35

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Hi guys,

New to the forum. Picked up my first V35 350gt(2003 Coupe 6mt Bone stock) in Australia last week (Had an Infinity G35 in States). Absolutely love the car, mechanically it is immaculate, drive and shift smooth.

Today I notice an issue with Climate control. When i adjusted air con temperature from 18 to 28, i could barely feel any change, air was really cold all the time. Until i set it to 29, I could finally feel a bit difference. When i set it to 32, vents started blowing warm air but it was moderate. Also I notice that once AC is on, the compressor will not kick off, it stays on all the time unless ac off. I thought , compressor should switch on and off to adjust temperature.

Any thoughts? Please help, thank you!

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sonicii Veteran

sonicii

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Posted

These cars use a variable displacement compressor, they don't regulate temperature by turning the compressor on/off, the cooling power is adjusted by varying the compressor displacement. A bit like an inverter air conditioner for a house. So the compressor is always engaged when the AC is turned on.

That said, i have found most car ACs with climate control will turn on the AC compressor for at least the first 5 minutes after switching it on, regardless of the temperature setting. Probably for situations where you are using the AC to dry the air (defog windows) rather than just for cooling, usually the system will engage the heater at the same time.

Also keep in mind, CC systems usually have some 'smarts' built in, they monitor the external air temperature, and detect sunload, so they may blow cold air, even if the interior cabin temperature is at or below the current set point, in anticipation of the heating effects of outside air and sun. They don't wait for the cabin to get hot before reacting.

MightyV35 Contributor

MightyV35

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  • Author
Posted

These cars use a variable displacement compressor, they don't regulate temperature by turning the compressor on/off, the cooling power is adjusted by varying the compressor displacement. A bit like an inverter air conditioner for a house. So the compressor is always engaged when the AC is turned on.

That said, i have found most car ACs with climate control will turn on the AC compressor for at least the first 5 minutes after switching it on, regardless of the temperature setting. Probably for situations where you are using the AC to dry the air (defog windows) rather than just for cooling, usually the system will engage the heater at the same time.

Also keep in mind, CC systems usually have some 'smarts' built in, they monitor the external air temperature, and detect sunload, so they may blow cold air, even if the interior cabin temperature is at or below the current set point, in anticipation of the heating effects of outside air and sun. They don't wait for the cabin to get hot before reacting.

Thanx for the response, Sonicii. Hummm, that's really interesting. anyway i did check the cabin air sensor underneath the steering wheel, it all hooked up. BTW, how do you monitor the reading from interior temp sensor?

sonicii Veteran

sonicii

Posted
Posted (edited)

I don't think you can in normal operation, but I believe you can go into the diag mode and see what temperature it is reading from the sensors.

I have attached the page from the FSM which may help.

atc.pdf

Edited by sonicii
MightyV35 Contributor

MightyV35

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  • Author
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I don't think you can in normal operation, but I believe you can go into the diag mode and see what temperature it is reading from the sensors.

I have attached the page from the FSM which may help.

Appreciated! Had a check, all three temperature sensors work fine.

MightyV35 Contributor

MightyV35

Posted
  • Author
Posted

I don't think you can in normal operation, but I believe you can go into the diag mode and see what temperature it is reading from the sensors.

I have attached the page from the FSM which may help.

Hi, I did check all three sensors again closely, when i ran test 2, it displayed 20 which i believe means all sensors are functional. But when i ran test 51, outside temperature sensor reading is 44(Actual temp is around 33), Cabin temp reading is around 36(Actual around 30 inside), MAF temp is around 26. Since outside temp is always displayed on center console, i found after a quick drive the out temp dropped from 44 to 34. However once I start the self diagnose again, the readings are inaccurate again. Is this means something wrong with the outside sensor and cabin sensor?

sonicii Veteran

sonicii

Posted
Posted

the outside sensor will be impacted by engine heat when you stop.. it is mounted in front of the radiator, which is why you see it drop fairly quickly once you start driving again.

Cabin temp sensor is near your left knee when in the driver seat, so you would need to ensure you are checking the temperature from around the same area.

It is unusual for these items to be inaccurate, normally when the sensor fails.. it fails properly..

chiefster1976 Apprentice

chiefster1976

Posted
Posted

This may not be your problem but worth a quick look!1

I had either really cold at 18 degrees but even on 18.5 onwards the temperature was blowing hot air... After further investigation

the sensor 2 pin connector under the steering wheel had bent one of the pins hence not working the sensor properly...

Check the connector pins and make sure they are not bent.... Once I reshaped my pins the climate worked fine!! Cheap fix..

worth a look hey!! good look....

No power to my AC at now at all. im stumped... ;-(

Good luck !!!!

MightyV35 Contributor

MightyV35

Posted
  • Author
Posted

This may not be your problem but worth a quick look!1

I had either really cold at 18 degrees but even on 18.5 onwards the temperature was blowing hot air... After further investigation

the sensor 2 pin connector under the steering wheel had bent one of the pins hence not working the sensor properly...

Check the connector pins and make sure they are not bent.... Once I reshaped my pins the climate worked fine!! Cheap fix..

worth a look hey!! good look....

No power to my AC at now at all. im stumped... ;-(

Good luck !!!!

Sorry to hear that your ac not work. Anyway thanx for the hint, I will look into it.

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