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Old 01-15-2017, 06:52 PM   #8
mikeshaw
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Re: 01 Chevy Venture Cooling Fans & AC Not Working

Quote:
Originally Posted by brcidd View Post
If you buy a refill kit- attach the gauge hose to the low side port (do not open can valve) and read the system pressure, you'll know if it has any refrigerant pressure in it. If it reads zero- all refrigerant is gone. If it reads above 47 psi, then you have at least enough to activate the compressor. From here- I will say you have less than 47 psi, since compressor does not come on.

If all refrigerant is gone- you have a massive leak- listen for hisses if you decide to add some.

You can add to a system where compressor is not running- the pressure from the can will pressurize the system to activate the compressor.

Also you can have a system that reads 80 psi and only have 5% of the needed refrigerant in it. This is why it is important to "weigh in" the refrigerant- to get the correct amount in the system.
Thanks again for the feedback. I have put this AC issue aside for a few weeks since it is January and can live without AC. But I have read that AC issue should be fixed ASAP because if there's a leak moisture can get into the system and create more problems.

I got back to it today and wanted to do as much testing as I could with the multi meter. I don't have a pressure gauge manifold. I managed to get to the low pressure switch/sensor which is located under the air box, had to remove the whole air box which was a PITA to put it back. But I uncovered the pressure switch. There was the required 5 volts to the switch and ground was good, but there was no continuity on the switch. Another indication of low pressure.

If it's low pressure I was wondering if there's at all any possibility that it could just need a recharge. Perhaps if it were a very slow leak then a simple recharge would do the job. I have read that a small amount of leakage is normal in any system over the years. I've had this vehicle for 8 years and never had any service on the AC.

But the AC seemed to stopped working suddenly. As I recall it was blowing as cold as usual up until it suddenly stopped working. I assume it would have gradually become less cold before the low pressure switch would disengage the system.

So I was wondering if I could just add some refrigerant to see if the AC clutch engages. You have hit upon just what I was considering to do - get some refrigerant and see if it will take a charge. But everywhere I've looked the instructions say the compressor must be engaged already while adding refrigerant. You are saying that I can add to a system where the compressor is not running and the can's pressure could cause the compressor to engage. I have read about this in one place and it says that the radiator fans must be running for this to work. On my vehicle the radiator fans are not turning on until the coolant temp reaches about 226F. Can I add the refrigerant without the radiator fans running? Or Should I let the vehicle run and heat up until the radiator fans turn on ?

Regarding how much refrigerant to add, the Haynes Repair Manual simply states "Never add more the 2 (12Oz) cans of refrigerant to the system. Seems rather vague. You mentioning weighing the refrigerant, I assume using a scale to measure how many Ounces. But the repair manual doesn't even specify how many ounces, just "never add more than 24 Ounces".
How to know exactly how much refrigerant to add ?
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