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I just bought an East Coast 2002 that I posted on another thread.
The A/C was blowing hot air (the outside temp is very hot for SF Bay Area...90 degrees). I placed a canister with gauge on the low port with engine running and a/c set to Max AC, Cool, High. The gauge read 10psi. I shot in R134a per instructions on can. As I did, I could hear and see the compressor cycle on and off. I filled to just under 45psi on the gauge. As the compressor cycled (about every 5 seconds the gauge would fluctuate between 5psi and 45psi. After the recharge, I drove for about 10 minutes on the freeway at about 65 mph. The air never got cold, it seemed to get cool, but the outside temp was around 70. The inside temp was 73.
I just bought an East Coast 2002 that I posted on another thread.
The A/C was blowing hot air (the outside temp is very hot for SF Bay Area...90 degrees). I placed a canister with gauge on the low port with engine running and a/c set to Max AC, Cool, High. The gauge read 10psi. I shot in R134a per instructions on can. As I did, I could hear and see the compressor cycle on and off. I filled to just under 45psi on the gauge. As the compressor cycled (about every 5 seconds the gauge would fluctuate between 5psi and 45psi. After the recharge, I drove for about 10 minutes on the freeway at about 65 mph. The air never got cold, it seemed to get cool, but the outside temp was around 70. The inside temp was 73.
Now what?
Thanks!
Cheers!!
The low-pressure port pressure reading you're looking for is while the compressor is running disregard any readings when the compressor is sitting still. At 70° I wouldn't while using only the low-pressure port for measuring go over 30-35 psi.
Is it normal for these compressors to cycle so frequently .....every 5-8 seconds?
Each of my other vehicles (Acura TL, Land Cruiser, Range Rover), the compressor ran, for the most part, constant when on in my driveway.
I miss read how you stated it had 45psi on the low side, I thought that was with the compressor running, but obviously not if it then dropped to 5psi (compressor running). It needs to be around 35-40psi when the compressor is running.
It needs to be around 35-40psi when the compressor is running.
That number is not absolute, it depends on a number of variables. "Normal" might be 25 psi or it might be 60 psi depending on those variables or may "cycle".
The low pressure cycling switch operates by closing when the pressure passes through the 40-45 psi range ascending. That's supposed to activate the compressor clutch which runs the compressor. When the compressor runs, it pulls the low side pressure back down. If it reaches 20-25 psi descending, the switch opens to prevent evaporator freezing and the pressure starts to climb again until the pressure ascends to 40-45 psi again at which the cycle can repeat.
If ambient temps and the cooling load are both high, it's perfectly normal for the switch to remain closed and for the compressor to operate 100% of the time and there will be no cycling. Just because there is static pressure doesn't mean that the system is properly charged, though. It only means there's enough refrigerant in there to cause the gas pressure to register.
When you first start the system, the pressure in the system is at it's "static" level which can be determined using an R134a Pressure-Temerature chart as the static pressure is determined by the temperature of the gas in the system. Static pressure must be above the set-point of the cycling switch for the system to begin operation.
In general, two things will turn the clutch off. Hi pressure and Lo pressure.
To get your state of charge, check pressure without running the engine ie: first thing in the morning or after the vehicle has sat idle for some time, allowing the system to equalize. At 70 ambient, system pressure should be about 70 psi.
If 2 cans of do-it-yourself recharge does not make it better, you are probably looking at taking it to a shop. Unless you have access to an evacuation machine.
Look around the ac piping and hoses for an oily area, indicating a leak.
as a general rule, when you put the gauge on the system, the low side will be about 100 psi without the motor or compressor running. When you start the compressor, the pressure will drop as the gas is sucked thru the pump. If it drops below about 20 psi, the compressor will kick out. Add more gas. If you have enough gas, the gauge will stay around 35 psi constant and will seldom kick out........... all the above will happen in a 85 degree ambient........... as mentioned, the numbers change a little as the ambient changes.
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