134a Conversion

[Locked and Loaded]

I converted from R12 to R134a in my 1990 Grand Wagoneer. All the info on low and high pressures that I have found are for R12. Does anybody have a chart or know the pressure ranges of the low and high pressure side at about 90 degrees? I think I'm still a little low but want to be sure.

[babywag]

from oljeep.com...pretty lacking chart doesn't take into account for relative humidity

[Locked and Loaded]

Thanks. Is tis for 134a?

[babywag]

yes

[DieselSJ]

You should be charging by weight and not pressure. There are too many variables that affect pressure. Ballpark is use 80% of the R12 capacity when converting.

[DieselSJ]

[FSJunkie]

If you have a sight glass, just charge it until the bubbles stop and then about another 1/4 can.

Or if you don't have a sight glass, charge until the system doesn't seem to cool any better if you keep adding more. These expansion valve systems either have enough refrigerant to cool, or they don't have enough refrigerant to cool. There isn't much in-between.

[Ronaldwag]

Pardon my ignorance but what do you mean by manual to manual transmission conversion? Is it not always that when you convert transmission it is from automatic to manual?

[babywag]

Originally Posted by FSJunkie

If you have a sight glass, just charge it until the bubbles stop and then about another 1/4 can.

Or if you don't have a sight glass, charge until the system doesn't seem to cool any better if you keep adding more. These expansion valve systems either have enough refrigerant to cool, or they don't have enough refrigerant to cool. There isn't much in-between.

sight glass is useless with r134a there will always be bubbles.

[FSJunkie]

Originally Posted by babywag

sight glass is useless with r134a there will always be bubbles.

No there won't. A proper charge of R134a will not show bubbles in the sight glass. My converted systems don't bubble.

The reason you're getting bubbles on your system is because the person who charged your system followed the rule of using less R134a than R12 on a converted system, which only applies to orifice tube A/C systems, not expansion valve A/C systems like all our Jeeps have. That means you do not have enough liquid refrigerant inside the receiver/dryer for it to do it's job and feed only liquid refrigerant to the sight glass and expansion valve.

Orifice tube systems (accumulator after evaporator) use less R134a than R12.

Expansion valve systems (receiver/dryer before evaporator) use the same charge.

[JeepJeepster]

So much information, excellent thread.

[marsupilami]

Sorry for hijacking this thread.

I am also rebuilding my AC with new hoses, condenser, drier, etc. Only the evap is the original one.

Now I put it all together and wanted to have it pressure tested.
As I have no Nitrogen available, I had this done at a shop. Unfortunately, the system is not building up any pressure, so there is a leak somewhere...
Now, I really don't know if the guy who did it knew what he was doing.

Therefore my question how to properly pressure test an empty System?

I think the expansion valve is open now, so there is no high and low pressure side, right? So what is the proper pressure to test it? Can I put 160PSI on the high port, or just 40 PSI on the low port?

Is there a possibility that the AC guy blew up my evap during testing?

Can I also use pressured air to test myself? I have a drier on my compressor, so moisture should be minimal.

Any hint is much appreciated...

[JeepJeepster]

Could the guy not tell you where the leak is? Do you have a vacuum pump?

Suppose if I were in your situation, I would pull a vacuum on the system and see just how bad the leak is. If it will hold vacuum for any point of time I would go ahead and fill it up with 134a with dye in it. Buy the little leak detection light/glasses from amazon and try to find the leak.

Highly doubt he blew anything up.

[TexasJ10]

Originally Posted by JeepJeepster

Could the guy not tell you where the leak is? Do you have a vacuum pump?

Suppose if I were in your situation, I would pull a vacuum on the system and see just how bad the leak is. If it will hold vacuum for any point of time I would go ahead and fill it up with 134a with dye in it. Buy the little leak detection light/glasses from amazon and try to find the leak.

Highly doubt he blew anything up.

I agree. Pull a vacuum for an hour or so to dry it out, and then see if it will that vacuum overnight. If it does, fill it up to proper pressures. Do not try to pressure test with compressed air. Nothing but bad will come from it.

[Locked and Loaded]

Originally Posted by FSJunkie

No there won't. A proper charge of R134a will not show bubbles in the sight glass. My converted systems don't bubble.

The reason you're getting bubbles on your system is because the person who charged your system followed the rule of using less R134a than R12 on a converted system, which only applies to orifice tube A/C systems, not expansion valve A/C systems like all our Jeeps have. That means you do not have enough liquid refrigerant inside the receiver/dryer for it to do it's job and feed only liquid refrigerant to the sight glass and expansion valve.

Orifice tube systems (accumulator after evaporator) use less R134a than R12.

Expansion valve systems (receiver/dryer before evaporator) use the same charge.

I find it hard to believe that you did something other that stock on your Waggy. Welcome to the 1990s.

[babywag]

Originally Posted by FSJunkie

No there won't. A proper charge of R134a will not show bubbles in the sight glass. My converted systems don't bubble.

The reason you're getting bubbles on your system is because the person who charged your system followed the rule of using less R134a than R12 on a converted system, which only applies to orifice tube A/C systems, not expansion valve A/C systems like all our Jeeps have. That means you do not have enough liquid refrigerant inside the receiver/dryer for it to do it's job and feed only liquid refrigerant to the sight glass and expansion valve.

Orifice tube systems (accumulator after evaporator) use less R134a than R12.

Expansion valve systems (receiver/dryer before evaporator) use the same charge.

no r134a in either of my jeeps, still r12.

we used to install vintage air systems @ resto shop I worked at.
they were expansion valve systems.
they had 2 different charge capacities for r12 & r134a on exact same system.

i have never read or heard anyone say converted systems should receive the same charge for r134a before. have read/seen many manufacturers call for lower charge capacity w/ 134a.
so not real sure where you're getting your info?

should always charge by weight when possible.
there is a reason aftermarket systems and newer cars don't use them.

[FSJunkie]

I understand the principle behind using less R134a in a converted system, but I also know how the receiver/drier's job is to make sure that only liquid refrigerant leaves on the way to the expansion valve. It can only do that job if there is enough refrigerant (whatever it may be) in the system to keep the outlet tube submerged inside. If I see bubbles in the sight glass on the outlet of the receiver/drier, that tells me gas is going to the expansion valve, and gas doesn't cool at all. The expansion valve only works with liquid, so at that point I see that I need more refrigerant. Even if I overcharge the system, it's just going to pool liquid refrigerant in the receiver/drier and that doesn't hurt anything. System pressures don't increase any further because the liquid and gas are in equilibrium for the temperature conditions.

This isn't anything I've read or heard about, this is my own method that I've developed with experience and logically thinking about how the system works. It seems to work great...my systems cool well I've never blown a hose, seal, or compressor.

It's not my intention to argue with you or say your methods are wrong, I'm just saying this seems to work great for me.

On a side note, my Pontiac has an early orifice tube system and it is picky as heck about it's charge level. The book says 4 lbs for full charge, but I got the best cooling and compressor duty cycle with less than 2lbs. If I put 4lbs in it the accumulator would frost, the evaporator wouldn't get very cold, and the compressor ran all the time. It was not happy.

[babywag]

Originally Posted by FSJunkie

This isn't anything I've read or heard about, this is my own method that I've developed with experience and logically thinking about how the system works. It seems to work great...my systems cool well I've never blown a hose, seal, or compressor.

It's not my intention to argue with you or say your methods are wrong, I'm just saying this seems to work great for me.

Not arguing, or dissing you, but I've done a LOT of AC work over the years.
I wouldn't follow that advice. Overfilling a system leads to higher pressures, and will reduce it's effectiveness, it can also damage the compressor.

Doing a few systems doesn't really justify your opinion on how to charge a converted system.
Glad that it worked for you, but it may not work for others.

I took training for work, classes @ school, and worked on vehicles for a living. It's best to follow the manufacturers recommendations for AC work.