76 Scamp A/C

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Well, I guess that old RV-2 came back to life! If you are really getting 30 degree air out of the vents, the evaporator is going to freeze up. It's kind of hard to believe it's really getting that cold with only 12 oz. of R-134A. What are you measuring the vent temperatures with?

Did you put the EPR valve back in? If not you will need to put a cycling switch in to measure the evaporator temperature and cycle the compressor clutch to keep it from freezing up.
 
Pete in NH said:
Well, I guess that old RV-2 came back to life! If you are really getting 30 degree air out of the vents, the evaporator is going to freeze up. It's kind of hard to believe it's really getting that cold with only 12 oz. of R-134A. What are you measuring the vent temperatures with?

Did you put the EPR valve back in? If not you will need to put a cycling switch in to measure the evaporator temperature and cycle the compressor clutch to keep it from freezing up.
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Yes, it definitely came back. I have one of those little thermometers that you stick in the vent to measure the temperature. For ice, yeah the whole thing was covered in it last tonight. Today that it's hotter, it's only getting down to 50 at the vent, but that's a ton better than the outside temp. I did leave the EPR out and I do plan to put a cycling switch of some kind on it, but first I want to see how it does as is. It currently doesn't get driven more than around the block and let sit and idle because there's no insurance or plate on it, but that's going to change in a few weeks. I also hooked up all of the vacuum lines today so the heater is working again as is the EGR valve. I don't think it's all that important for something this old, but I'll see if it makes a difference since I had been driving without it. And I must say, it feels like a whole different car driving with the windows up and cold air coming from the vents. The last chore of the day was replacing the sending unit it the tank. I had bought a new one maybe three months ago and just did it today. The original had the float full of gas and the electronics or whatever in it were shot as well; resistance was all over as I was moving it. So, new one in, took it to the gas station (it wasn't far) and watched the gauge slowly come up as I was filling it. Now all that's left is all of the rust and a carb kit since it's leaking.
 
Added another can in because it couldn't get under 60 in the 90 degree heat we had today, and it's cooling down better, but might take another can. I'm also wondering, where do I get a thermostat that will cycle the compressor? The only thing I can find at work is for a radiator fan and I'm not too sure, but I don't think it works how I want it to.
 
I didn't think 12 oz was going to be enough R-134A. You're probably going to need somewhere between 24 and 36 oz.

The cycling switch you're looking for was used on earlier A body cars. Some thing like ackits.com part numbers 32-20916 or 32-20904. So, look for a switch for an early 70's A body. It will have a capillary tube that goes into the evaporator cooling fins and mounts on the outside of the evaporator case. It gets wired in series with the compressor clutch power feed.
 
Well, it's been awhile since I got it working and the front seal gave out on the compressor; I guess I know where that aluminum bushing went now. But, I went to O'reilly and bought a reman unit and put it on with a new drier. After fighting leaks at the inlet, outlet, and service ports, it seems to be working. There is something that confuses me though. Running, there is 10-15 on the low, about 200 on the high, ice under the hood, and about 60 degree air out of the vents. I don't have a cycling switch yet, but I would think that it should get much colder than that inside. Would unhooking the heater help any? I had hooked it up after the last compressor had quit just to see if it worked, so the temp before was always taken without coolant in the heater.
 
You want to make sure you have no hot water flow through the heater core or the A/C will be trying to overcome the heater.

How much R-134A did you charge the system with after changing the compressor? Your low side pressure at 10-15 pounds looks on the low side. Did your new compressor come with a EPR valve installed internally. A true 76 A body compressor would have an EPR valve. Before about 1974 A body cars used a cycling switch after that they went to an EPR valve like the B and C body cars.
 
Pete in NH said:
You want to make sure you have no hot water flow through the heater core or the A/C will be trying to overcome the heater.

How much R-134A did you charge the system with after changing the compressor? Your low side pressure at 10-15 pounds looks on the low side. Did your new compressor come with a EPR valve installed internally. A true 76 A body compressor would have an EPR valve. Before about 1974 A body cars used a cycling switch after that they went to an EPR valve like the B and C body cars.
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I think that the heater valve is sticking open some because both hoses are hot, but I also don't know which one should have the valve on it. Without being in front of the car, I believe I have it on the one that goes to the water pump. The new compressor didn't come with an EPR valve and the old one is rusted over and basically trash. I charged the system with 36 ounces of R134a and one of those little cans that's supposed to be an ester oil charge just because I had spilled some when I was filling it before it went on the car. I still need to get a cycling switch and I thought someone had posted a link to one in this thread, but I can't seem to find it, so I'll just do some research on that.
 
Okay, without the EPR valve you will need the cycling switch. I gave you two part numbers in a post above in this thread.

36 OZ. of R-134A may be a bit too high for this system as that is the full R-12 charge and R-134A is usually somewhat less. What type of oil did the compressor come filled with? Mixing oil types is not a good idea.

Some compressor come with a shipping oil, whatever that is. Or, it may have been filled with mineral oil for the original R-12. I always drain a new compressor and flush and fill with the correct amount and type of oil to match the refrigerant in use.
 
Pete in NH said:
Okay, without the EPR valve you will need the cycling switch. I gave you two part numbers in a post above in this thread.

36 OZ. of R-134A may be a bit too high for this system as that is the full R-12 charge and R-134A is usually somewhat less. What type of oil did the compressor come filled with? Mixing oil types is not a good idea.

Some compressor come with a shipping oil, whatever that is. Or, it may have been filled with mineral oil for the original R-12. I always drain a new compressor and flush and fill with the correct amount and type of oil to match the refrigerant in use.
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I thought there were some links, must be too blind to see them. I had to go to an appliance part place to get a new thermostat for my drier, and he had the kind of cycling switch that I needed. It did come with a shipping oil that looked like motor oil, but I drained that out and put in ester oil. I'm gonna put the switch in tonight and see what happens.
 
Cycling switch is in and it's cold enough that I can see frost coming out of the vents. I removed the resistor on the front of the box to install it, and I discovered a secondary issue that was also the cause of a noisy blower fan. The whole box was full to the top with leaves! It never occurred to me even though I knew the car had been parked under a tree for 15 years. After seeing that, I'm surprised that the evaporator hadn't rotted through.
 
I've never seen "frost" coming out of the vents, so I'm not sure what that's about. It does sound like getting the leaves out of the evaporator case have helped things out though. With the cycling switch in place the compressor should cycle on and off. When the vent temperature gets down into the mid 30's the compressor should cycle off.
 
Pete, the frost, out the vents happens down here in the south, when the humidity is very high. The cold air coming out the vents condenses the humidity in the air right at the vent outlet. But actually it should not occur, if the evap temp control is set correctly. I don't like to see the discharge air below 40 degrees, as the discharge air temp is typically 5-10 degrees warmer then the evap temp, and you don't want evap freeze up.
 
Hi Charrlie,

Thanks for the explanation on the "frost". I don't know how you folks down there live with that kind of humidity! We never see that kind of humidity up here in New Hampshire.
 
Pete in NH said:
Hi Charrlie,

Thanks for the explanation on the "frost". I don't know how you folks down there live with that kind of humidity! We never see that kind of humidity up here in New Hampshire.
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It's a common thing down here. Most of the time my glasses fog over when I get out of a car that had the a/c running. I have the switch set so it cuts out around a vent temp of 35 and it's back on around 40. Now I just need to get a new belt and all should be done on this one. Next is my truck which needs the entire system installed. The compressor blew up after 9 months so I ripped out everything since it's all under warranty. This makes the new compressor the 10th one to be on the truck since it was new in 1989. GM's R4 is a terrible compressor, I've had two different once last less than 5 hours.
 
76Scamp said:
I have the switch set so it cuts out around a vent temp of 35 and it's back on around 40.
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I would suggest, you set the temp for off at 40 and back on at 45. At the setting you have now the evap is running below freezing. When we get into summer, the compressor will run longer, and it might slug liquid refrigerant back to the compressor, which will blow the valves, even if the evap doesn't ice over.
 
Charrlie_S said:
I would suggest, you set the temp for off at 40 and back on at 45. At the setting you have now the evap is running below freezing. When we get into summer, the compressor will run longer, and it might slug liquid refrigerant back to the compressor, which will blow the valves, even if the evap doesn't ice over.
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I would, but the switch I have doesn't go any higher than 39. He did give me a second one along with the one I bought, but he didn't know anything about it and there wasn't any paperwork with it. All he knew was that he bought it about 10 years ago and never used it, so I might try that one and see what it does. But before this at night, it'd be ice from the expansion valve all the way to the compressor and the compressor itself would be sweating. During the day it's not as bad, but now with this switch on it, it shouldn't do that. Right now it needs a new belt because even though I thought I had it tight, it was loose and ended up just slipping and now it's worn out.
 
Well, I should've know better than to run the 40 year old hoses and I paid for it today. Going down the road in comfort when I stop at a light and hear a loud hiss and there's a sort of smoke from under the hood. I pulled over and the high side hose out of the compressor gave up. If I have a day off next week, I'm going to drive it up to Classic Air in Tampa and see what they'd charge for just replacing the hoses. I don't care what it looks like as long as it's going to work.
 
Along with 40 year old hoses your system may have been overcharged, 36 OZ of R-134A is equal to the R-12 capacity and you usually use less R-134A in a conversion, especially with the original serial flow condenser. You have to watch your discharge side pressure on a converted system. High ambient temperatures with too small a condenser for R-134A can cause the discharge pressures to get really high. The EPA mandates a high pressure cut off switch on converted systems although many times the switch is not installed.
 
Pete in NH said:
Along with 40 year old hoses your system may have been overcharged, 36 OZ of R-134A is equal to the R-12 capacity and you usually use less R-134A in a conversion, especially with the original serial flow condenser. You have to watch your discharge side pressure on a converted system. High ambient temperatures with too small a condenser for R-134A can cause the discharge pressures to get really high. The EPA mandates a high pressure cut off switch on converted systems although many times the switch is not installed.
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Actually, for what I'm adjusted to, it actually seemed like the pressure was low; 10 on the low side and just under 200 on the high. My truck that I converted usually runs at 30 on the low and 250 on the high and it'll get under freezing in there, but then that's on a 1990 S15 with an R4 compressor and the whole system has been replaced. So now that this happened to it, I'm gonna drive it up to Tampa and see what they can do for me. I'm gonna let them know that I'm to the point that I don't care what it looks like as long as it work.
 
Hi Charrlie,


No, not an A/C professional, I’m self taught since I seized up the RV-2 compressor in my 71 Charger back in 1984 due to lack of oil and ignorance of A/C systems. The compressor ran out of oil and seized up fried the clutch. I found the hole in the bottom of the condenser later that caused the whole issue. I found I could buy the replacement parts and tools for less than it would have cost to have someone else repair the system. So, a reman. compressor, EPR valve, new clutch, dryer, condenser along with a vacuum pump and gauge set and I was all set. Over the years the tools have more than paid for themselves in maintaining the automotive A/C systems in the family. Phased into R-134A as R-12 disappeared and R-134A came in on newer cars. I still have the 71 Charger and it’s still R-12. No one around here will touch an R-12 system anymore. So, I have the ability to recover R-12 and still have a 30 pounder of R-12. Over the years I’ve added electronic and U/V leak detectors and have my 609 certification. I come from an engineering background and have learned that automotive A/C work isn’t all that hard to learn. I’ve also seen that many of the local shops that do A/C work aren’t really A/C professionals but more like general repair shops that also do A/C work. I often have a better understanding of how to do something properly than they do. These days no one really understands these the old Chrysler RV-2 systems so I try to pass along what I’ve learned over the years.
 
I stated doing auto A/C back in the late 60's early 70's. Then I branched out into residential and commercial/industrial A/C & R. I also still do R-12 systems. I can also rebuild most hose assemblies. I am certified in both 609 and 608. Have worked on everything from little under the counter refrigerators to multiple hundred ton industrial chillers. But I am cutting back on the work. The newer cars have the A/C systems controls tied in with the ECM, and it is just too expensive to upgrade my diagnostic equipment, to use on a part time basis, and now that R134a is going to be phased out for 1234yf, that will mean buying all new equipment, again. So, I will just stay with the older cars, untill I put my tools away.
 
I agree, when r1234yf really rolls out I'll be done too, along with almost everyone else in the DIY area. So far the r1234yf introduction has been a bit of a fiasco. The stuff is very expensive and the German carmakers are now citing safety issues with it. I suspect over the next few years as r1234yf comes in and R-134a gets phased out R-134A is going to get expensive like R-12 did. It might be time to put some R-134a aside to keep our existing vehicles going. I can see a big move to HC refrigerants by DIY folks as R-134a goes away. I don't know much about HC's so I don't know if that will be good or bad. But, I can see pricing is going to drive people that way and the HC producers will be ready to take advantage .
 
Pete in NH said:
I agree, when r1234yf really rolls out I'll be done too, along with almost everyone else in the DIY area. So far the r1234yf introduction has been a bit of a fiasco. The stuff is very expensive and the German carmakers are now citing safety issues with it. I suspect over the next few years as r1234yf comes in and R-134a gets phased out R-134A is going to get expensive like R-12 did. It might be time to put some R-134a aside to keep our existing vehicles going. I can see a big move to HC refrigerants by DIY folks as R-134a goes away. I don't know much about HC's so I don't know if that will be good or bad. But, I can see pricing is going to drive people that way and the HC producers will be ready to take advantage .
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I know what you mean. I plan on stocking up on 134 as soon as I can.
 
76Scamp said:
There is a switch on the drier, but I would think that's just so the system doesn't run when it's empty.
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You're right. It is a low pressure switch. Earlier models did not have it.

The RV2 is a good compressor, much better than what Ford and AMC ran at the time. Not quite as smooth as the GM axial compressor of the day, but a bit more durable. Though all of them worked adequately, they were hp pigs. The Nippondenso/Sanyo compressors that are ubiquitous today need about half the horsepower to maintain the same level of cooling comfort.
 
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