Air Conditioning Question

[Lin]

This is not for the bus.  I won't even pretend it is for the toad, but what rpm should the engine be at to test the low pressure refrigerant pressure?  What should that pressure be at 100-110 degrees?  Thanks

[justin25taylor]

If you are using 134a I would start at 35-40psi on the low side at idle. You really need to know the high side pressure to make sure the system is happy. Hope this helps.

[Nick Badame Refrig/ACC]

Hi Lin,

Justin is correct but, if you want it exact, you need to scale in the proper ounces by the spec plate for your system.

You may not have the equipment to do so but, by gussing you may easily overcharge the system and damage the compressor.

If possible, bring it to a qualifed service garage to evacuate the system of any non condencibles and scale in the proper charge.

I'm not sure weather you just leaked refrigerant, or had to open the system for some reason. Either way, if just leaked some out,

R-134A is a blended refrigerant and you may have leaked more of one property then the other and should be recharged as I discribed above.

If you had to open the system, you will have air in the system which is a non condencible and will effect the proformance of the system.

Good Luck
Nick-

[Lin]

Thanks for the info.  We have been having an above 110 degree heat wave, and my wife's Volvo AC cutout.  I only have a low pressure gauge, so when it started working after things had cooled down to a pleasant 108-109 degrees, I checked the pressure which was about 45 PSI at idle.  Since the reading is a bit lower as the rpm's increase, I wanted to be sure that doing it at idle was correct.  I could not find any spec plate.  Also, at idle, the vent air temp was only about 70, but dropped down to 60 at 1500 to 2000 rpm.  I was actually concerned that there may have been too much R134, and that it was cutting out due to high pressure.  Maybe this AC system can't handle over 110 degrees though.

[Nick Badame Refrig/ACC]

Hi Lin,

With over a 40 deg. drop from outside ambiant temps, I would say that it's giving you all it has...

Keep cool..
Nick-

[justin25taylor]

I am sure Nick will agree, this has been the hottest summer I remember in 35 years. when I am not traveling I have a small HVAC service company. I mainly do residential/RV/Bus stuff and about 80% of my calls have found the system working as it should. It is just super hot right now.

I can offer a few suggestions:
Keep controls in car set to "max". Override the climate control if it has one to use max until car begins to cool off. Some cars switch to max automatically with climate control, some don't. I am not too familiar with Volvo stuff.
Park in shade
Tint windows
use one of those sun-blocker things that go over the windshield when parked.

Finally, If you feel the car a/c is not working as it should, take it to someone who knows auto a/c's and they can re assure you it it is working ok.

Best,
Justin