[indyav8n]

Is there any air conditioning specialist in the forum?

I need some help reviving my AC on the 70 GP, Not sure how long it had not been working, there was residual pressure in the system. So I replaced the compressor seal, serviced the oil in the compressor, replaced the expansion valve, and replaced the dryer. I did not however replace the POA valve. Then I evacuated the system and it held good at 26 inchs overnight.

Serviced with 12, but it will not cool....gauges indicate low @ 80, Hi @ 135, one of the the books I saw says it should be low 140/ Hi 300. The only thing I noticed is the line coming out of the expansion valve at the bottom going to the Evaporator would frost over. I never remember seeing this before, normally the POA valve would get cold and frost up, but it never did.

Any help would be appreciated, Wes

[SAAC2110]

When you charged the system under vacumn how did you charge it, did you use the small 12 ounce cans, thirty pound bottle or a charge cylinder? also did you introduce it as liquid or vapor?

Are the pressures you mentioned in the posting with the a/c pump on and also how long does the pump cycle or stay on?

Steve

[indyav8n]

Steve,
I am using the 12 oz cans, however when I was not getting the results I thought ( ie any cooling at all), I stopped at 4 cans. Which is a lb short or so short of the 4 1/8 lbs requirement. I introduced it as a gas on the low side, the compressor ran continuously. The pressures were while the compressor was running on a 65 degree day. My thought is I should replace the POA, I don't think it's opening. Even though I seem to have good flow past the sight gage, maybe overhaul the compressor in addition to the POA.

Wes

[SAAC2110]

That was what I was wondering about with your readings - first you are right about the POA valve assembly, a good indication the POA is failing is the low side pressure being high and the high side showing normal pressure with a running operating system. when the POA fails it vents high side pressure into the low side which even with a partially filled system will allow the compressor to operate. When you mentioned the expansion valve frosting, that was also an indicator- pressure too high on that valve.

Unfortunatley there are other things too consider - if you are using R-12 it has to be introduced as a liquid, if you are using charged 12 ounce cans of R-12 the can has to be inverted toward the discharging end - in other words once you attach the line to the can and open the valve turn the can upside down so the first thing out of the can is pure liquid. also loosen the line slightly until you get a bit of pressure to vent the air from the line. I also would immerse the cans in a container like a empty coffee can filled with pretty warm water since the cans are prone to frosting up while they empty themselves. Normal pressure for R-12 is 32-35 low side and high side anywhere from 150-185. Also look at your gauges while system runs, if either gauge needle is bouncing around eratically, it usually indicates pump problems but these old pumps were pretty much bullit proof.

Most important if you had vacumned the system down that long make sure you have enough ester oil in the system it never hurts to throw in a couple of ounces in for lubricating the system if questionable about quantity. --- running out of room so shoot me a PM with phone number with any other questions.

Steve

[gpmodelj70]

Why do you say R12 must be introduced as a liquid?...I have repaired several R12 systems...always as a gas...factory manual says to charge as a gas??

[SAAC2110]

Why better to charge as a liquid than gas, bottom line effiency and longevity.
When compressed gasses are introduced into a vacumned system as a liquid it actually takes less volume to acheive peak performance and lower high side pressures.
I also do the same charging method on cars in the shop that are 134A systems and the average car that requires 32-38 ounces of propellant in the systems I found I could use less propellant to acheive peak output performance ( cabin temperature ) on 26-28 ounces of propellant. While this is not that much difference in the quantity the thing that is of interest to me is the high side pressures are generally around 200 psi.
Another point of interest is I can monitor lower temperatures across the vehicles A/C condensor assembly which translates into less heated air drawn across the vehicles radiator hense I don't have to see the cars temperature gauge pegging to the hot side while the car sits in bumper to bumper traffic.
I'm not a rocket scientist so I can't explain how everything works, this is the method that works best for me for A/C servicing and I like the results from the cooling effiency and the lower high side pressures that save strain on the systems components, it also seems to last also since my own Jeep is still performing strong after four years when I replaced a leaking hose and recharged it.
Give it a try and see what you think and this does apply to R-12, 22 and 134A also and I'm outta beer and my fingers are cramping from typing all this so..... goodnite all