AC R-12 to R134a retrofitting

[mopar3.0]

yea theres a probley a low pressure swith in the system if the suction pressure is to low it wont let the clutch cut in, safey for the compressor, if the system is low it will cause the compressor to run hot and do damage, the switch prevents this. usually any were from 15 -30 psi is normal for the suction side with r134 depending on ambient temp and condenser temp

[mmtphoto]

earlier you had said that it was around 25, and i thought it should be around 40 on a gauge (crusty shadow said the same thing)-again, if no gauge, the sight glass works, just not as accurate as a good gauge. I read somewhere else on here that you should only fill it to 80 percent of what it should hold with r12 and there should be a sticker somewhere under the hood telling you what the r12 capacity is-

you should know, though, if you HAD a leak that was not fixed, you will lose refrigerant and it will cycle alot and get to a point where it will not engage the clutch.

[DiscoPanda]

I'm thinking of converting the R-12 system in my Caravan C/V to R-406a. Supposedly R-406a works better than R-12 even, and the lubricants are apparently the same, too.

[MoparGLH]

Ok,on the sticker in the engine compartment,it says it holds 30oz of R12 refrigerant,and each can of the R134A is 12oz x 3,so thats 36oz of R134a I put in.

[NAJ]

You should have put in 24 oz. of R134A (30 oz. x 80%)
R134A is more fickle than R-12. On the old R-12 systems if you overfilled the system it would get colder. R134A that is low or high will not cool efficently and the high side pressure may be running to high, if you do not have a set of gauges to check the high side pressure and the high side pressure is too high you may find out when sitting in traffic when air flow thru the condenser is reduced and it blows out the pressure relief valve.

[mmtphoto]

are you using gauges? if so, what are your readings? Is it still cycling off and on since you added the 12 additional ounces? Like me and others had said on here, gauges are the best way to determine if it is fully charged. Just because you put 36 oz in it doesn't mean it has that-it may have a leak. Do you see any 'oily' or wet looking areas near the ends of hoses, where fittings are together or where there are clamps? If the filter is plugged, it will not travel properly through the system and adding refrigerant will not make any difference. Did the system work properly before you took out the R12, or was it already not working properly? If so, you may need to find out if there is a blockage or leak before you can get consistant cooling.

keep us informed, at least it is changed over and will not cost an arm and a leg to work if you can figure out what is wrong.

[MoparGLH]

Ok,sorry,here I go again.
After I put in the last can of R134a,the gauge was still in the blue,just below 30,and the clicking on and off of the compressor continues.I don't see any leaks,but I think tommorow I will take it to get it checked for leaks.I looked up all the symtoms of a bad compressor and my compressor is showing no signs of any of those symptoms.I also ran across this article:



it's important to note that on some cars, it's normal for the A/C compressor clutch to turn on and off during system operation. These types of cycling-clutch systems turn the compressor clutch on and off to regulate the flow of refrigerant into the evaporator. Since theses systems use a fixed orifice tube, it can't regulate refrigerant flow on its own. You can tell this type of system by a periodic clicking at the compressor clutch, as it turns on and off. Frequent clicking on and off of the compressor clutch, however, usually indicates a system that is low on refrigerant charge.


If there was a leak in my system,would'nt there be signs of the oil leakage also because Ive looked everywhere and I do not see any oil leakage anywhere.And How could I still be low on refrigerant after putting in 3 12oz cans of the R134a.I'm sorry,I'm new to this whole A/C thing.Like I said,I will have it checked tommorow for leaks and low refrigerant and everything else.

[MoparGLH]

Quote:

Originally Posted by mmtphoto are you using gauges? if so, what are your readings? Is it still cycling off and on since you added the 12 additional ounces? Like me and others had said on here, gauges are the best way to determine if it is fully charged. Just because you put 36 oz in it doesn't mean it has that-it may have a leak. Do you see any 'oily' or wet looking areas near the ends of hoses, where fittings are together or where there are clamps? If the filter is plugged, it will not travel properly through the system and adding refrigerant will not make any difference. Did the system work properly before you took out the R12, or was it already not working properly? If so, you may need to find out if there is a blockage or leak before you can get consistant cooling. keep us informed, at least it is changed over and will not cost an arm and a leg to work if you can figure out what is wrong.

Ok,my bad,it says it holds 34oz of R12.No,I did check for leaks and I do not see any telltale signs of leaks anywhere.No,the system never worked up until now when I did the retrofit.I will try to post up pics if i can to show you where the gauge sits at while I was putting in the last can of refrigerant ,but it was below 30.

[mmtphoto]

again, it has been awhile since I have done one of these changeovers, but-if you can get readings on low and high sides, it will probably be fairly easy to figure what needs to be done-

also, don't just check it while idling, drive it so that air is cooling the condenser, or at least run a garden hose in the front of the radiator to get an idea-can you measure the temp coming out of the vent? do you have the system set on 'max'? If you are getting 38-40 degrees, especially when driving, I would not worry about it too much-if higher, replace the orfice tube first (the filter)-it is almost always the problem, and that is also an indication of extremely high readings on the high side. like i said earlier, I am a little rusty on this stuff, so, (hopefully) others will jump in here-

[MoparGLH]

Ok,here is the gauge reading with the car running and the A/C on.






It was like 75 degrees today,so it should be at where the dial is set on the gauge.And gauge reading fluctuated when ever the compressor clicked.Yes,I will see if I can get the high and low port readings checked tomorrow.No,I'm going to buy a thermometer tomorrow also so I can check the vent temperature.thanks again

[NAJ]

The system uses a cycling clutch. when the low side reaches a pre-determined pressure(by low side cut off switch) the switch opens cutting power to the compressor, as the pressure rises the switch closes again completing the circuit to the compressor, that is how evaporator(low side) pressure is maintained.
In an A/C system pressure and temperature are directly related, if the low side dropped too low the evaporator would freeze.Our cars also use a thermal expansion valve that opens and closes to control the amount of refrigerant entering the evaporator.
Be sure you do not see any lines freezing, frost on a line indicates a restriction. Condensation is normal.
Also the molecular structure of R134A is smaller than R-12 so a small leak with R-12 will become a larger leak with R134A.

[Realest]

also no one mentioned a high pressure cut-out
r134a runs a lot higher head pressure then r12.....can get as high as 400-450psi easily.
the systems i work on have a high pressure cutout/fan cut in switches...usually cutting the fan in anywhere from 350-450 psi.
i recommend at least wiring in a pressure switch to cut the clutch out for when stopped in traffic. to prevent system damage. lack of air flow over the condesor causes the pressure to climb rapidly

[NAJ]

Agreed, a lot of cars have had to have "pusher fans" installed to aid in condenser cooling especially on vehicles with small frontal grill areas.

[mmtphoto]

Realest and NAJ, +1+1

-if you can get readings on High/Low ports and vent temp readings, along with observations on freezing/evidence of leaks, etc, you will be able to solve this-(probably super high 'high' from the sound of it)-
these guys will point you in the right direction with more information,-it is early June, it is probably a matter of orfice tube replacement, or a blockage that can be found/fixed.

I am reading this with interest because I am about to tackle mine-haven't turned it on yet, and am in the market for a suction pump so I can go over mine. Lots of good information here.

[MoparGLH]

I was going to ask too,I have a MP Logic Module installed.Would this affect the A/C's electronics in anyway?my computer is a mopar performance logic module P4532327.What are the specs on this LM?