1972 Duster Build with my Daughter

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Wow.... Fixed the AC today, got in to take it for a test ride and nothing when the key was turned on. Looked at the ignition switch connector and in less than 1000 miles the damn thing melted the plug on the main power feed. I figured the original melted ones were just because the harnesses were old. I pulled the 5 large gauge wires out of the plastic connectors on both ends and looked at them. The spring tension on the Standard replacement ignition switch sockets sucked. The M&H harness pins were nice and tight. Well after thinking about it we put some heat shrink on them and soldered the 5 large high current connectors together. Man I am glad that did not happen on the trip last week...... That connector style is really just crap.
 
Damn it.... the guy we got the Duster from is offering to trade services for the next project for the wife....... Doing the bodywork and some detail work on his 383 Barracuda......

So for the price of doing the bodywork and painting/restoration of 2 cars I get one free.... I need a bigger garage!
 
Wow.... Fixed the AC today, got in to take it for a test ride and nothing when the key was turned on. Looked at the ignition switch connector and in less than 1000 miles the damn thing melted the plug on the main power feed. I figured the original melted ones were just because the harnesses were old. I pulled the 5 large gauge wires out of the plastic connectors on both ends and looked at them. The spring tension on the Standard replacement ignition switch sockets sucked. The M&H harness pins were nice and tight. Well after thinking about it we put some heat shrink on them and soldered the 5 large high current connectors together. Man I am glad that did not happen on the trip last week...... That connector style is really just crap.
So nobody makes a connector that will hold up then?
 
Damn it.... the guy we got the Duster from is offering to trade services for the next project for the wife....... Doing the bodywork and some detail work on his 383 Barracuda......

So for the price of doing the bodywork and painting/restoration of 2 cars I get one free.... I need a bigger garage!
Which car do you get for free with this deal?
 
Crap. I’m in love. I will have one of these in the garage before I know it for the wife......
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Way too hot for a car show. Kaelyn was loosing it so we left and got ice cream.

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Spent some time with the factory AC today. I think a couple A/C guys on the FBBO site and I have figured this out. For those using factory A/C converted it to 134a and it worked like crap I may have a step by step of how to modify the replacement expansion valves to work as good as if R12 was in the system by next weekend.
 
I have heard people say to just take the EPR valve by the firewall out, and straight pipe it? Don’t know if that’s the correct way, but I have heard more than one person say it.
 
I have heard people say to just take the EPR valve by the firewall out, and straight pipe it? Don’t know if that’s the correct way, but I have heard more than one person say it.
The EPR valve is inside the compressor and yes you must take it out.
 
Ok story so far. I have gone through 2 compressors and 2 expansion valves on the Duster. The compressors where my fault and the valves where to experiment because the AC worked like crap from the day put the first can of freon in it. I have been talking with a couple of the guys on the B-Body site who have worked in the AC business for a long time and I think we have the problem. I have my Coronet that will cause icicles to form on my nose sitting next to the Duster which is lucky to put out 55 degree air.

Through these two I have learned what sub cooling and super heating is and how to measure it. What we found was there was 30 degrees of superheating (evaporator) when there should be about 10. The subcooling was about 10 degrees (condenser) which was about right.

There was no reason why it should not be working. Finally we gave up and I modified my Murray (O'Rilley) expansion valve to close down the orifice by a significant amount. The modification was a hack and now that I pulled the 4 Seasons valve apart I understand how it is suppose to work. When I pulled both valves of the box I french kissed both of them to blow through and see how much restriction where was. I was sort of surprised to find almost no restriction but did not understand AC enough at the time to put 2 and 2 together. Back to the experiment. The AC worked 100% better. The pressures where correct and the outlet of the evaporator was frosty cold and sweating just like I would expect! That is when the thought went into the expansion valve.

I thought about how the valve should work. If the temperature probe is too warm (like room temperature in my hand) the valve should be choking off the liquid freon like crazy to try to get a huge pressure drop converting the freon back to a gas which requires energy by absorbing heat (read... effective cooling, an AC does not make cool it absorbs heat from the air). When the probe starts to freeze it should move the orifice so there is less of a pressure drop (opens up the valve) so it can flood more liquid freon and not use as much energy and not pull as much heat out of the evaporator. That said at room temp the orifice should be closed off trying to get a huge pressure drop. Well the 2 new and original valve in my had at room temperature I could blow though the valve with almost no noticeable restriction at all..... The modified one I could detect a noticeable restriction trying to blow through it. We where on to something.

One thought I had was maybe these cheap aftermarket valves were just poor in tolerance stack up in manufacturing and the orifice was been held open too far when the probe was hot.

Here is my experiment with the 4 Seasons....

The orifice is SUPER simple and it is adjustable but you have to open the system to try a new adjustment.....

An allen wrench to remove the nut and a spring and pressure plate pops out. Thin needle nose pliers to grab the orifice ball and the orifice and pin are removed. That is all there is. The temperature probe and equalization pressure tube are connected to the valves rear diaphragm. As the R134a in the probe heats and cools it move the diaphragm pushing on the end of the pin and orifice ball to open/close it.

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Notice the seating surface for the ball is on the same side as the pin! The pin must be able to go back into the valve enough such that the back edge of the ball contacts the brass seat

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Here is the orifice pin installed

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I found if I pressed down on the ball with the allen wrench that the air flow restriction went way up.... Like I said is the problem a tolerance stack up problem with manufacturing?

I measured the orifice and it was 0.963" long.

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I then got out my dremel tool and ground it down to 0.949" long or removed 0.014" of length.

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Now when I put the orifice in and put a bit of pressure on it I could barely blow through it! Now we can make some Freon gas!

Here is the pressure plate with a cup machined into fit onto the orifice ball. The spring and nut adjusts how much pressure is pushing against the diaphram to fine tune the sub cooling temperature.

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So you can count how many turns the factory put the nut in for preload on the spring but with the ball setting 0.014" down in the bore I am not sure if that buys you anything anymore. I threaded it in until it made contact with the spring and threaded it in 2 complete turns of preload. I will setup to measure the sub cooling when I install it and see where I am.

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I likely won't get to install or test this until later this week but there is a show at Little Anthony's Diner Saturday night that Kaelyn really has been dying to go to so it needs to be working by then!
 
Nice write-up! I am working on my AC right now as well. My evaporator seems to be freezing up. I ordered a new drier and expansion valve. I'm hoping to get some cool air while going down the highway. Best of luck and thanks for the insight. I hope you get it straightened out for the show. Kaelyn has a beautiful car and a wonderful experience helping to create it!
 
Quick update. I had a bit of time tonight so i decided if 2 turns in was good maybe 4 would be better. Put in a can of freon and I think I am way to far the other way not (not allowing the orifice to open enough) as the output side of the valve is frosty cold instead of the output side of the evaporator, I think the freon is changing state to gas completely in the valve instead of the evaporator. Need to pull it apart and back off the spring tension on the adjustment hex nut tomorrow night and pump it back down and try again.
 
Update, still struggling. Quickly found out 0.014" is way to much. New valve bought today and started with 0.005" and we have frosty sweating lines but still about 10F too much super heat so I think I am going to take off another 0.003 and see what happens.....
 
Who are you getting your valves from and what brand? I picked up parts from Vintage Air while I was home as they are about 45 min. From the house.
 
Who are you getting your valves from and what brand? I picked up parts from Vintage Air while I was home as they are about 45 min. From the house.
Probably the same. One was a Murray (ORilleys) and the other was a 4 Seasons (Local auto parts) they were basically the same with a bit different metering pin design. Bought a new Murray from ORilley yesterday and it was the same design as the 4 season so I think there are 2 basically the same valves that everyone rebrands.
 
About par for the course, wish we were about producing quality over quantity.
 
Found the lower limit, sweet spot and the upper limit to the grinding on the metering valve. We got about 15F cooler with this modification. Now to see if working some of the details can bring it down any more. Outlet of the evaporator is about 40F-45F when it was 85F out last night. It was at ~55F. Going in is still quite warm so the average across the evaporator is not where the Coronet it yet.
 
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