Starting My A/C conversion to R-134A

[NMF250IDI]

So far I know I should...

Flush the system, lines and coils...bought a can of "clean & Flush" from Auto zone. Do I need to remove the Condensor and Evaporator Coils for this, or can it be done in place ?

Replace the Accumulator/drier, pretty straightforward, any difference in brands ?

Switch to a variable orifice... any difference in Brands ?

First big question....Do I need to drain the oil out of the compressor...and if so is it just a matter of tipping on end ? Seems like if I have to flush the mineral oil out of the lines I'd surely need to get it out of the compressor as well. The label on the back of the compressor indicates it takes 7 oz of oil. Should I use the same quantity of R-134 compatible oil ?

 

[SparkandFire]

I would definately try to get as much mineral oil out of the system as possible... pull the compressor and turn it by hand until you are comfortable that most of the oil is out... put 7 oz of "Castrol Retro AC Oil" or a similar Ester oil, which is somewhat tolerant of trace amounts of mineral oil remaining in the system.

Your on the right track though, flush everything and replace the filter/dryer and expansion orifice.

Some good reading on the subject... http://www.id-usa.com/how_to_faqs_retrofitting.asp

 

[NMF250IDI]

I flipped the compressor over and rotated it by hand...just a few drops came out. I'm trying to figure out if the oil went somewhere else...or maybe I just can't drain the compressor this way.
I guess I'm worried that if I add R-134 compatable oil without removing the mineral oil I'll wind up with too much oil in the system .

I did some more reading and I think I had the wrong idea about the oil in the compressor. Is it true that the compressor doesn't really have an internal resevoir of oil...the system oil just moves around with the refrigerant ?

 

[SparkandFire]

I did some more reading and I think I had the wrong idea about the oil in the compressor. Is it true that the compressor doesn't really have an internal resevoir of oil...the system oil just moves around with the refrigerant ?

Yes and no... There is always some oil in the compressor, but it does move around as a vapor throughout the system as well... That's why if you have a leak somewhere, it will be oily. If you don't get all the old oil out it's ok, just put 7oz back in. From what I have been told, it's always better to have too much oil in the system than not enough! The extra oil tends to accumulate in the reciever dryer, which doesn't hurt anything!

Now, on a York system the oil stays in the crankcase... You can actually drain and refill the crankcase, and check the oil regularly on a York compressor...

 

[SparkandFire]

[

I did some more reading and I think I had the wrong idea about the oil in the compressor. Is it true that the compressor doesn't really have an internal resevoir of oil...the system oil just moves around with the refrigerant ?

Yes and no... There is always some oil in the compressor, but it does move around as a vapor throughout the system as well... That's why if you have a leak somewhere, it will be oily. If you don't get all the old oil out it's ok, just put 7oz back in. From what I have been told, it's always better to have too much oil in the system than not enough! The extra oil tends to accumulate in the reciever dryer, which doesn't hurt anything!

Now, on a York system the oil stays in the crankcase... You can actually drain and refill the crankcase, and check the oil regularly on a York compressor...

 

[NMF250IDI]

The big chill...

Flushed everything except the condensor ( just lazy ), but I did blow a bunch of dry air through it. Drained the Compressor , maybe a tablespoon of oil in there. Changed all the o-rings, new accumulator and a severe duty VOV from NAPA. Pumped the system down overnight, verified it held a vacuum for 45 min. Put in 36 oz of R134..80% of R12 charge.

Seems to be working great...around 38 coming out of the vents on max air ( No heater bypass ). Not very hot outside when I tested it, so that number could change.

While I still have the gauge set...Whats the proper setup for the pressure switch ? Right now it cycles from ~30psi up to 50psi. What sort of pressure readings should I see on the High side ?...I have a chart from Ford but I think it's for R-12.

 

[RLDSL]

Flushed everything except the condensor ( just lazy ), but I did blow a bunch of dry air through it. Drained the Compressor , maybe a tablespoon of oil in there. Changed all the o-rings, new accumulator and a severe duty VOV from NAPA. Pumped the system down overnight, verified it held a vacuum for 45 min. Put in 36 oz of R134..80% of R12 charge.

Seems to be working great...around 38 coming out of the vents on max air ( No heater bypass ). Not very hot outside when I tested it, so that number could change.

While I still have the gauge set...Whats the proper setup for the pressure switch ? Right now it cycles from ~30psi up to 50psi. What sort of pressure readings should I see on the High side ?...I have a chart from Ford but I think it's for R-12.

Forget the chart . With a vov it won't mean squat. Your high side pressures will drop therfore your low side pressures will read high. You just have to go by temp. Put a temp probe in the center duct and monitor the duct temp run it on max cool with the windows up Once you get it to where it's cycling, you want that switch cycling off somewhere around 16-21 psi so you turn the screw until the pressure begins to drop between cycles, if it doesn't add more refrigerant a tiny bit at a time, watch temps at the duct carefully , if at any time duct temps get hotter, them charge has got too much. if the duct temp gets to 33 deg ( and it very well may if you have a pusher fan )stop there , you do not want it to go below that or the evaporator will ice.
If you have a big box fan, set it in front of the condenser while charging and setting the system, it will help.

 

[OLDBULL8]

All this worry over changing to 134A is a bunch of BS. EPA says to evacuate, but if the system isn't cooling or the compressor won't cycle there is very little refrigerant left in the system if any. It's a known fact the shaft seal would dry up and leak from inactivity on the older vehicles. Since the 90's I think, the compressor will cycle when the heat is on to keep the shaft seal lubricated, another EPA mandate. When 134A first was mandated by EPA there was a lot of confusion about changing the hose and O'rings because 134A is smaller molecules and would leak out, not so. I've changed over a lot of vehicles and never once evacuated the system. Of course if the system has been opened on any part of it then evacuation is required to get any air out. Just add the 134A and Ester oil for lube, forget the PAG oil left in there. I charge the system until a frost forms on the line coming out of the evaporator, then release some gas until the frost disappears. Never a problem with any of them. Lots of cold air. As long as you get a 20* difference between ambient temp and cold air, thats as good as any system will do.

Just my .02 cents worth. Anyone have change for a nickel?

 

[Andrew M. Frankli]

My experience is the same as oldbull8 except for one thing: 20 degrees is what I would consider the MINIMUM differential between air temp @condensor and evaporator. I routinely get 30-35 degrees differential on healthy older 134a systems.

 

[Agnem]

So you guys are just saying I should go to NAPA, get one of those R134A conversion kits, hook up the fittings, pump in the bottle and I'm done?

 

[OLDBULL8]

That's what I'd do. Make sure you put the oil in. Some cans of 134A come with the oil already in there.

Note: Go to the Lounge, read the Arizona drug war. Interesting.