Are these A/C charge pressures right?
Thread Starter
Joined: Dec 2010
Posts: 0
Are these A/C charge pressures right?
1996 4 cyl, non-VTEC:
My A/C didn't seem to be cooling enough, so I checked the low-side pressure, and observed compressor switching: Compressor ON for 6-8 seconds w/pressure falling, stopping around 27-28 psi....Compressor then switches OFF, and pressure climbs to around 45-47 psi, then compressor switches back on and off with same readings.
Temp here in Houston today was 101 F, and tomorrow it'll be 105 F, with @ 65-75% humidity. Yep.
Temp during test was 79 F w/ 65% humidity @ 1:30AM, and I added a can of 134a freon because I know psi should be closer to 32, but can vary up to around 50, depending on ambient temp/humidity. After adding 1 can of 134a, low-side pressure still rose and fell like before, with no change in timing of compressor OFF/ON, but when ON pressure now only drops to around 30-32.
Is the rising pressure when compressor OFF like that normal? Is that the system equalizing pressure as I've heard? Why have I heard that Stop Leak will "do more harm than good" ? Would it be safe to add another can of 134a, this time with an oil charge? Also, what type of refrigerant oil is required, please? Sorry for the peppered questions. I want to add another can, but don't want to overload the system. Thank You!
My A/C didn't seem to be cooling enough, so I checked the low-side pressure, and observed compressor switching: Compressor ON for 6-8 seconds w/pressure falling, stopping around 27-28 psi....Compressor then switches OFF, and pressure climbs to around 45-47 psi, then compressor switches back on and off with same readings.
Temp here in Houston today was 101 F, and tomorrow it'll be 105 F, with @ 65-75% humidity. Yep.
Temp during test was 79 F w/ 65% humidity @ 1:30AM, and I added a can of 134a freon because I know psi should be closer to 32, but can vary up to around 50, depending on ambient temp/humidity. After adding 1 can of 134a, low-side pressure still rose and fell like before, with no change in timing of compressor OFF/ON, but when ON pressure now only drops to around 30-32.
Is the rising pressure when compressor OFF like that normal? Is that the system equalizing pressure as I've heard? Why have I heard that Stop Leak will "do more harm than good" ? Would it be safe to add another can of 134a, this time with an oil charge? Also, what type of refrigerant oil is required, please? Sorry for the peppered questions. I want to add another can, but don't want to overload the system. Thank You!
Last edited by gigem891; Jun 7, 2011 at 01:44 AM. Reason: grammer
Thread Starter
Joined: Dec 2010
Posts: 0
Thank you, hondadude. I am going to get a dual-pressure gauge, since I'll be doing most A/C maintenance on this and wife's minivan. I think I've figured it out. Am I reading that Service Bulletin correctly, so that with only 10-15 psi, A/C vent temps could, or should be in the grey area shown? How is that possible? Wouldn't that be an undercharged system?
Super Moderator
Joined: Sep 2006
Posts: 16,328
From: Houston, TX
You want to mark a vertical line at the ambient temperature reading and a horizontal line for the high pressure reading. The lines should cross in the gray zone. This chart shows the a/c running with the engine at 1000 rpm.
The same for the temperature blowing at the vents and the low pressure reading on the gauge.
One of the links in the online manuals thread in the DIY section has a 94 shop manual that has a more detailed graph to use specific for your car. It also has more details about the readings.
The same for the temperature blowing at the vents and the low pressure reading on the gauge.
One of the links in the online manuals thread in the DIY section has a 94 shop manual that has a more detailed graph to use specific for your car. It also has more details about the readings.
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