A/C High Pressure Fluctuation


Old 06-09-11, 02:48 PM
Thread Starter
Join Date: Jun 2011
Location: USA
Posts: 2
A/C High Pressure Fluctuation

I just recharged my A/C using a kit and I have the high pressure and low pressure gauge manifold from harbor freight tools.

It appears to be working great, but I want to make sure everything is working 100%

Today it was about 55 degrees fahrenheit outside (I know it was a bad time to do some tests on the A/C on such a cold day). I had the air going full blast and the low pressure read 30 psi with no fluctuations at all in pressure while the high pressure would fluctuate between 140 and 185 psi constantly. Is this normal operation or do I have too much, or too little R-134a in the system.

Thank You
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Old 06-14-11, 06:43 AM
billys68ss's Avatar
Join Date: May 2003
Location: USA
Posts: 1,459
That sounds about right. Alot depends on the vehicle. Some run higher high side pressures than others. The low side reading is your refridgerant charge and should always be above 20psi at idle but never above 40... again some systems may run a little higher but this is my experience. Im sure that when the high pressure would fluctuate you will also notice that the cooling fan (radiator) will also turn on to prohibit the pressure from going to high. If you dont have an electric fan on this vehicle then you most likely wont notice that but if you stand near the engine compartment you will feel a difference in the amount of air moving from the fan as well as the temp of that air. This is perfectly normal operation.
Hope this helps ya,

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