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MBDiagMan

MBDiagMan on Mon May 24, 2010 10:38 AM User is offline

Year: 1964
Make: Ford
Model: Galaxie 500
Engine Size: 289
Refrigerant Type: R134a
Ambient Temp: 80
Pressure Low: 10
Pressure High: 220
Country of Origin: United States

I have pieced together an a/c system for this old relic. I have a Ford brand 66 Mustang underdash unit, a parallel flow condensor, sanden compressor, binary switch on r/d in series with clutch wire from underdash unit for actuating the clutch.

Before piecing together the a/c I had installed a killer 6 blade fan direct with no fan clutch, that pulled enough air you could hold your hand out the window with the engine idling and feel a breeze from the fan. After the condensor was in place, I could feel air blowing FORWARD from the condensor with engine idling. I ran the idle speed up to about 1,500 RPM without a fan in front of the car and got the readings entered above. It cooled like crazy but then the evaporator froze up. I found that in messing with the underdash unit, I had pulled the thermostat sensor almost completely out of the evaporator so it could not sense freezing, thus did not drop out the clutch.

I have fixed the thermostat (de icing switch) and suspect the low side problem to be improper condensor/radiator flow. The condensor is mounted about 3/4 to 1 inch from the radiator. Will moving the condensor closer to the radiator fix this flow problem (assuming that it is a flow problem) or do I need to use some foam weatherstrip around the edges of the condensor to force the air through?

Thanks in advance for any help that anyone can offer.

-------------------------
Have a great day,
Doc
ASE Master

TRB on Mon May 24, 2010 12:29 PM User is offlineView users profile

How much refrigerant do you have in this system?

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MBDiagMan on Mon May 24, 2010 12:46 PM User is offline

1.5 pounds by charging scale.

-------------------------
Have a great day,
Doc
ASE Master

TRB on Mon May 24, 2010 12:55 PM User is offlineView users profile

If you used a true vaned PF condenser I would say you are low on refrigerant. Those systems took about 24 ounces of R12. You should be able to get close with the right condenser.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

MBDiagMan on Mon May 24, 2010 2:32 PM User is offline

Since it has 1.5 pounds (24 ounces) in it now, will I be in any danger of running the high side too high if I add some more?

Thanks VERY much for your help!

-------------------------
Have a great day,
Doc
ASE Master

TRB on Mon May 24, 2010 2:42 PM User is offlineView users profile

I think you can add a few ounces without any issues. The low side should be around 18 to 20 at idle and 14 to 17 at a fast idle. You are close in my opinion now.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

MBDiagMan on Tue May 25, 2010 7:33 AM User is offline

Well there seems to be something wrong that I don't understand. It doesn't take much for me to not understand.

I set up a high volume squirrel cage fan in front of the car, ran the idle up and set up a cannister of 134 on my charging scale with gauges and all set up. I started it up and pressures were about 220 and 10 like before. I added 2 ounces and the high side went to 450 very quickly. The service ports are right at the compressor and the binary switch is on the r/d. Could there be restriction between the high side port and the switch that would prevent the switch from seeing the high pressure and interrupting the clutch circuit?

When I cobbled this thing together I put about 3 ounces of PAG in the condensor and about 3 ounces in the evaporator. Surely the oil couldn't be causing any blockage.

I recovered a little at a time until the pressures were back at 220 and 10, but it wouldn't cool any better than about 60 degree vent temp. The hoses on my recovery machine tank are not long enough to let me set the tank on my scale, so I have no clue how much I recovered to get it back to the original pressures, but it seemed to be quite a lot.

When I did the original charge and put in 1.5 pounds it showed 40 degree vent temp and froze the evaporator since I didn't have the deicing switch line all the way into the evaporator.

I'm pretty puzzled, as I said, that doesn't take much in my case.

Thanks for sharing your experience.

-------------------------
Have a great day,
Doc
ASE Master

mk378 on Tue May 25, 2010 8:53 AM User is offline

The low pressure could just be because the evaporator / TXV is a bit too small for the rest of the system. You do have the TXV sensor bulb attached to the side (not the top or the bottom) of the evaporator outlet line, right? Improper TXV installation can lead to low pressures and suboptimal cooling.

As long as you're getting cold air don't worry about it being 10 psi. What is the system like at normal idle-- that's how the car will actually be used of course.

MBDiagMan on Tue May 25, 2010 9:00 AM User is offline

Thanks for the repy MK!

The TXV sensor line goes down into the evaporator unit seemingly as it was put in at the factory.

You offer good comments about my testing methods. I think I will just let it idle without the squirrel cage fan and see what I can make it do.

-------------------------
Have a great day,
Doc
ASE Master

MBDiagMan on Fri May 28, 2010 7:27 AM User is offline

Okay, I had a leaking oil pressure sender on the engine and had to wait for it to come in. I got the engine running again and in the process repositioned the condensor about 3/8" from the radiator and stuffed foam rubber most of the way around. This helped a BUNCH and I got the pressures more in line. I am now at about 220 high, 21 low, but that is with the squirrel cage in front of it and the engine at a fast idle, maybe 1,000 RPM. Without the fan on it, the high side is about 235 with the low side about the same.

Before getting the results above, I recovered the charge, evacuated and charged 1 pounds 8 ounces. The pressures were lower than those in the paragraph above and the vent was 60 degrees. I added about another 3 or 4 ounces in small steps to get it to where it is. The last ounce of that made no improvement in vent temp.

Doing this I managed to get 47 degrees at the vent with the car setting still. When I drive the car the best I can do is 55 degrees at the vent. This is all at about 85 to 90 degree ambient.

Following up on the suggestion of the expansion valve line attachment, it is currently inside the evaporator assumedly as it was placed at the factory. Since the pressures seem reasonable, could the expansion valve be the problem? Do I need to maybe replace the expansion valve or route the expansion valve sensing line on the side of the outlet hose as you describe? Would it work if it were attached to the side of the evaporator ouline if it is a rubber hose rather than a steel line? I have a recovery machine and would replace the expansion valve in a heartbeat if I thought this was the problem. Would a TXV made for 134 be any different and add any performance?

I've worked hard to get everything on this car right, but this a/c performance is just not going to work.

Thanks a bunch for any help you can offer.

-------------------------
Have a great day,
Doc
ASE Master

Edited: Fri May 28, 2010 at 10:56 AM by MBDiagMan

MBDiagMan on Fri May 28, 2010 7:57 PM User is offline

Since the low side pressure is slightly higher than what TRB said, and the TXV is over 40 years old, should I replace it?

-------------------------
Have a great day,
Doc
ASE Master

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