Altima Air conditioning

Well... you really need to get a set of gauges on the unit... but it sounds like you have a restriction in the system. This would cause the suction (low) side of the system to be much lower in pressure than normal... and trip the low-refrigerant switch as you have described.

What should the high and low pressures be? I just got a set of gauges.

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Well... that depends on several things... the blower motor speed... and the ambient temperature. Set the blower inside the car to the first (min) speed. What is the ambient temperature at your testing site? What are your gauge readings?

How do you know you filled it properly with the right amount of Freon. I assume the system is 134a refrigerant?

Well... that depends on several things... the blower motor speed... and the ambient temperature. Set the blower inside the car to the first (min) speed. What is the ambient temperature at your testing site? What are your gauge readings?

His original post claimed he had filled up the system and there was no change in the compressor cycling frequency.

Yes it was 134a and I had a low pressure gauge when I filled it. Just not a high pressure gauge.

Well... what are your answers to these questions?

The temperature is 75 degrees outside.

With the switch jumpered and the AC on with blower on high the low side is reading 30psi and the high side is 130psi.

When the system is off both gauges read 105psi.

I hope this helps...I am guessing blockage, but I am not sure.

Thanks

It is true that temperature and humidity conditions will affect pressure readings a lot. Never the less, pressure ranges can be given for systems designed to use a specific refrigerant, given that manufacturers tend to optimize systems for maximum efficiency.

For R134, low side pressure readings are normally between 30 and 40 psi, and high pressure readings can go from 150 to 250 psi, even though tables show wider ranges.

A typical dual pressure switch will turn off under 25 +/- 3 psi and over

I think that your system is low in refrigerant. Bring the low pressure to 35 or so just to make sure that the press. switch is not cutting off on the low side.

Please share your results.

Good luck

snipped-for-privacy@gmail.com wrote:

replace the thermo control amp and get the system charged by weight not pressure

Those pressures indicate no blockages... and appear pretty normal. I agree with Nisstech about the thermo control amp. That is the device that monitors the evaporator temp... and cycles the A/C clutch appropriately.

I have jumpered the thermo control amp and the system works great!! Is this a dealer part? I should not just leave it jumpered right?

Thanks again for all of your help...

My feeling is that that part is a dealer item... and therefore won't be cheap. You really can't leave the jumper in. It won't damage the system... but in high humidity conditions... the evaporator core will freeze. When this happens... the airflow through the core will drop to almost nothing. You would notice this inside the car when with the blower up high... hardly any air would be coming out of the vents. When the compressor is shut off in this condition... the core will thaw... and normal operation will resume next time... until the core freezes up again. That is the entire reason that the compressor clutch cycles. Hope that helps.