I agree with you, if there is moisture in the system this will create the acidity in the refrigerant to go higher. A dryer is needed and a different orifice tube will be needed also.

 

Are those part numbers under the sticky the correct part #'s for the exp. valve that I need? And, one final dumb question for now, is the orphis tube part of the expansion valve, or are they just a different name for the same part?

 

You got a real mess there. We used to use R-11 to flush systems with. I am sure it is no longer available. Alcohol works good. The last A/C system that we changed over, we took the whole thing apart and flushed each component seperatly, manually, with trichlorethelene.... condenser, evaporator, compressor, hi and low hoses, expansion valve (TXV) and a new dryer. Proud Rebel is absolutely correct about the thermal expansion valve. It must be relaced with one that is designed for 134A. That is what regulates how much freon enters the evaporator. Try this
...http://www.explorerforum.com/forums/...p/t-77331.html

 

MJ, I just bought an expansion valve and dryer for my system when I converted it to R134a. I didn't have a part number, I just went to Advance and they gave me one for my truck and it was stamped R134a. It shouldn't be a problem.

And as to your question, yes, I'm pretty sure they are the same part. I think the dryer and the valve is around eighty, and very easy to replace. Just drain off as much pressure as you possibly can before opening up the system...cause that stuff is going to spray!! You'll also lose some oil, too. Which is a good thing in your case.

 

So, at Advance did you just ask for an expansion valve for a 91 Dodge, and it was compatible with 134, or did they list a different valve for R-12 ans R-134?

Rockfoot, how do you guys flush the system with alcohol? Do you just pour it into the system and put air pressure to it?

 

I don't remember mentioning R134a or R12. On their website, they show three different models. I'm pretty sure I bought the factory air model.

Click the link below to look at the different models.
http://www.partsamerica.com/ProductL...pe=393&PTSet=A

Towards the top of the screen you can change the vehicle to what yours is. Anyway, something that I missed when I bought mine, is the side that the low pressure switch is bolted on. You see the one in the middle doesn't show the mounting hole on the right hand side, so it must on the left. The other two both show the low cut off switch bolts to the right hand side. That's right up against the blower motor on my truck. I made it work, but it isn't pretty.

Just make sure you order the right one so you don't have any troubles.

Are you working on the 1992 model or the 1994?

 

The 92. For the price, it looks like the factory unit is the way to go. I have heard that it is the best.

 

Right, but you have to have room for that low pressure switch to mount on the right hand side of it. I bet your truck has it on the left hand side now. Look at yours now, you should see two wires going to the side of the expansion valve, either on the left or the right hand side. Match that up with the new one. Otherwise, you have to cut open the wire harness and butterfly the connectors to make it work and waterproof the connections with liquid electrical tape.

 

I can't believe how complicated this thread has gotten. It's an AC recharge not brain surgery. If you haven't torn the system down yet, go ahead and vacuum it to check for leaks. The 28 to 30 inches of vacuum is for sea level and is required to boil off the moisture. Since you are in South Dakota your vacuum will be determined by your elevation (in Denver you can get a max vacuum of 24 inches). Don't worry to much about the mineral oil left in the system. Get as much out as you can (would be nice to be able to remove the compressor and dump the oil). Mineral oil will not mix with either 134A or Ester oil. what gets picked up will drop out of suspension in the condenser or dryer and stay there. It is recommended in all the books that you don't attempt to flush the compressor or the hoses (especially hoses with manifolds). Change your dryer and H valve and pump it down. Jump the low pressure cutout and recharge with 134a (not recommended by Dodge because of the small condensers on our trucks). If your compressor is good and the condenser is not plugged then you should be cooling. Putting Your 2nd and 3rd can of 134a in a pan of warm water and placing a box fan to blow on the condenser will help to charge the system.

 

(Rockfoot, how do you guys flush the system with alcohol? Do you just pour it into the system and put air pressure to it?)
When we flushed the old oil out of the condenser and evaporator, we took them out of the vehicle and poured the trichlor thru using air to dry it out. A brake cleaner or contact cleaner will do the same thing, you just have to blow it thru the system and make sure you get it dry and clean... It took about a gallon.... we replaced the compressor... I wouldn't put trichlor thru a compressor...alcohol will work... Advance is where I bought my whole system... 134a...

 

The thing I would use is nitrogen and only nitrogen, it's inert and dry. You can purge the system with it and then check the system TOC ( total organic compounds), this way you can be sure that no R12 remains because it will boil off and there will be no oil residue. Just blow it with N2 (nitrogen) for a couple or three hours and it should be good.

 

Everyone is giving good advice, have worked on all A/C units. this is a simple switch. the oils are dont like to be mixed. They turn into a jelly looking mess. It Sounds like a problem I have had on conversions. Your filter/drier may have mosture and jelly oil in it. It now acts like a exspansion valve, this can be verified by feeling it. It will feel cool/cold or in bad situations frosts up. flush out the filter/drier with 99% alcohol you can buy it a pharmacy. It may take a few flushes to get the stuff out. Once you have the proper amount of freon in it look on the top of your filter there is a sight glass, on MAX air you should have very few if any bubbles. if there are bubbles you have Air or not enough freon.

 

Yup, the filter-drier does feel cold when the AC is running. That must be the problem. I ordered a new exp valve & dryer, so that should be taken care of. The problem that I have now run into is that the system must be leaking. I have taken two readings from the system (AC off), and the pressure has dropped. Also, the AC will not blow the slightly cold air that it did a few days ago when I attempted to charge it. I do not think that the system leaked this badly before and the leak seal-find with the freeze 12 may have fixed the small leak that caused the initial problems. I am thinking that it is may be a shrader (sp?) valve, since I could have messed one up while connecting to and disconnecting from fittings. A leak detector might be in order. Anyway, thanks to everyone for the help, and I will let you know how it goes!

 

The shrader valves like to get gummed up if you use any of the sealers. just remember when you take a pressure reading with a A/C unit off it will equilize from high side to low side. dont forget to clean out as much as you can with alcohol. my concern in this case is more the oil than water. and with a good vacuum pump the water will go away.

 

I borrowed a freon sniffer this morning and I did not pick up any significant leak. Unfortunately, I needed to work cattle this afternoon, so I did not have time to complete the repairs at the local wrenching place. But, I did get some alcohol and a tool to pressurize it into the lines and such, as well as the dryer and EV. So, first things first, I will evac the system good. At this elevation, I probably need about 26 in of vacuum, which my air compressor cannot handle (it only goes to 20 or so). I might need to use a neighbor's compressor. Anyway, hopefully it will work when I get the components cleaned and the new parts installed.