Do I need to change expansion valve?

[Some Car Guy]

I’m fixing the factory ac on my 69 GTX. Previous owner told me a local shop changed it to 134a. The old dryer was in a box of parts they took off doing various repairs on the car. The hoses look like they were changed at that time.

he told me when the work was done about 5 years ago that the ac worked good for about two years. Then needed charged the next year, then wouldn’t hold any pressure the next.

I found two black o rings, and one had no o ring at all. I got a kit of the green that came with oil and started changing them out. The expansion valve looks pretty old to me. I don’t know much about ac systems, but I thought you are suppose to change them when you change a dryer.

looking at pics online, the ones I’ve found so far look like you need to do some work to make them fit, like they are universal. Do any come as exact? I have limited garage time and try to have projects run as smoothly as I can to get the most done.

 

[Tman100]

If there has not been a failure with contamination in the system the expansion valve could very likely be used again.
Pressure test the system with nitrogen. If it holds pressure vac it and refill. I’ve used txv’s that are 65years old and they still work.
Just a fyi that txv is the same as used in some old IH tractors. I can’t remember the part# off the top of my head but I could find it with a little digging I’m sure.

 

[Sixpactogo]

New expansion valves are available that are an exact replacement. Most refrigerant people will tell you to replace it along with the dryer. The orifice in them is very small and they can easily get plugged up. For the $35.00 on Ebay it would be a no brainer for me.

 

[Some Car Guy]

Should I get a new dryer too since it has leaked so much since this one has been on?

 

[Sixpactogo]

Should I get a new dryer too since it has leaked so much since this one has been on?

I would. With the cost of refrigeration work these days you don't want to be doing things more than once.

 

[Jerry Hall]

I have converted several systems to 134. Change all O rings, questionable hoses and the dryer, after flushing the system, and changing the compressor oil. Test the system vacuum to be sure it's sealed. I have not had to change an expansion valve, but if a system has been open for an extended time, it's probably not a bad idea.

 

[WileERobby]

You can use the existing expansion valve. Although there is a difference in the size, it will work with 134 but not as efficient. The receiver drier MUST be changed, especially if exposed to air.

 

[Some Car Guy]

Is 2936469 a correct valve?

 

[Lefty71]

The dryer, on anything refrigeration-wise, should be replaced anytime it has been exposed to open air for a period of time, or anytime there has been a failure in the refrigeration system and it needs to be opened up and worked on. The new one will then filter out and retain any contaminants floating around the system. However, the contamination and moisture left must be very, very minimal.

The expansion valve, on the other hand, is an entirely mechanical device.... It may be just fine, and no need at all to mess with it, assuming it was working right previous to the system being opened up. The important factor here is that it is sized (which it will be) and it is designed for the refrigerant you desire to use.... All refrigerants have different characteristics and require different metering devices. If you are sure it's for R-134a, you will be fine.

Cleanliness is of the upmost importance.... if there is anything debris-wise moving through the system, the compressor will fail in no time if it's too much for the dryer to stop.


HTH, Lefty71

 

[Some Car Guy]

The dryer, on anything refrigeration-wise, should be replaced anytime it has been exposed to open air for a period of time, or anytime there has been a failure in the refrigeration system and it needs to be opened up and worked on. The new one will then filter out and retain any contaminants floating around the system. However, the contamination and moisture left must be very, very minimal.

The expansion valve, on the other hand, is an entirely mechanical device.... It may be just fine, and no need at all to mess with it, assuming it was working right previous to the system being opened up. The important factor here is that it is sized (which it will be) and it is designed for the refrigerant you desire to use.... All refrigerants have different characteristics and require different metering devices. If you are sure it's for R-134a, you will be fine.

Cleanliness is of the upmost importance.... if there is anything debris-wise moving through the system, the compressor will fail in no time if it's too much for the dryer to stop.


HTH, Lefty71

Knowing nothing more than I do, which is very little on ac, that would mean all the new on the shelf valves are for r12 like the NOS ones. I havent seen any saying they are for 134. Anybody know what I should use?

I just ordered a four seasons valve and dryer from rockauto since it will be here by Friday. It was only 50 bucks. I’m open to buying other stuff if it would work better. The nos valve would look good under there if it’s the right one. My car is very stock appearing.

 

[Lefty71]

I'm not sure about Mopars specific parts, but you may get away with using the R12 expansion (new or existing). Then charge your R134 to 90 percent of the factory R12 spec'd charge. This assumes that almost all of the factory components are intact, compressor, evap and condenser. Should be close enough to prevent damage... let us know how efficiently you think it operates after that.

 

[Jerry Hall]

All I can say other than my previous post is: Using the stock expansion valve, I'm getting 38 degree air at the vents.

 

[Some Car Guy]

I have a local guy that is a semi retired mechanic and happens to be a mopar guy that I’m taking it to to vacuum down and charge. I’m going to see what I can learn from him. Everything is stock style in this setup.

 

[YY1]

All I can say other than my previous post is: Using the stock expansion valve, I'm getting 38 degree air at the vents.

Hey, Jerry-

What pressures are you running?

After I changed my dryer due to a bad blow-off valve, I now get considerable condensation on the evaporator box.
Enough to drip. It's NOT a leak.

I'm at 48 on the low side and 225-ish on the high side.
Blows about 42-45 degrees at the vent.

AFAIK, it's the original expansion valve.

 

[Lefty71]

I'm at 48 on the low side and 225-ish on the high side.
Blows about 42-45 degrees at the vent.

Sounds good, but bear in mind that you cant compare apples to apples without knowing the ambient and weather when he took the pressure. You two could both be spot on, but comparing Florida to Canadia. Or Alabama in the winter, etc. Of course, RPM at measument does too.....and units need at least a few minutes to stabilize...

 

[WileERobby]

I've done a number of conversions over the years. From replacing almost everything, to just the receiver-drier. Every single job I did worked fine. See my post #7. YY1, depending on air-humidity content, you will get condensation, that's why cars are equipped with drainage, sometimes you see how much is under a car.

 

[YY1]

Sounds good, but bear in mind that you cant compare apples to apples without knowing the ambient and weather when he took the pressure. You two could both be spot on, but comparing Florida to Canadia. Or Alabama in the winter, etc.

Jerry lists Alabama as his location.

That's pretty close. That's why I asked him specifically.

I started at 50 on the low side but reduced it to 48 to try to combat the condensation issue.

It reduced the temp at the vents but didn't really help the condensation.

I was running 50 before the dryer change out.

My condensate drain is working fine.

The condensation I'm combating is on the outside of the box.

 

[Lefty71]

I started at 50 on the low side but reduced it to 48 to try to combat the condensation issue.

This is the double edged sword of refrigerants.... lower suction pressure means lower evap temps and more condensation (which is good, till it freezes). But you have to have enought in there to fill the evap.
To the other direction, higher suction pressures mean higher evap temps, but go too far and you slug the compressor and cause damage or instability at the least.
Condensation is desireable and typical as the unit works to lower the humidity in the cabin.

 

[WileERobby]

Jerry lists Alabama as his location.

That's pretty close. That's why I asked him specifically.

I started at 50 on the low side but reduced it to 48 to try to combat the condensation issue.

It reduced the temp at the vents but didn't really help the condensation.

I was running 50 before the dryer change out.

My condensate drain is working fine.

The condensation I'm combating is on the outside of the box.

Based on what you said, my guess is you may have blown out a clogged expansion valve, and now it's allowing more refrigerant into the evaporator.

 

[Jerry Hall]

Jerry lists Alabama as his location.

That's pretty close. That's why I asked him specifically.

I started at 50 on the low side but reduced it to 48 to try to combat the condensation issue.

It reduced the temp at the vents but didn't really help the condensation.

I was running 50 before the dryer change out.

My condensate drain is working fine.

The condensation I'm combating is on the outside of the box.

Your pressures are similar to mine, but ambient temperature, relative humidity and all play into the equation. Check your drain again as condensation on the outside of the box could be coming from a partially obstructed drain. Sounds like your system is working great.