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Possible bad expansion valve?

jvsutton on Thu June 23, 2011 10:02 AM User is offlineView users profile

Year: 1977
Make: Ford
Model: F100
Engine Size: 5.0
Refrigerant Type: r134a
Ambient Temp: 90
Pressure Low: 50
Pressure High: 175
Country of Origin: United States

First let me say that even though my truck is a 77 I'm not running a York compressor, I'm running an FS10 compressor from a newer truck. My truck is a Factory A/C truck. I posted this over on the Ford Trucks forum with not much response. For a little background I was running the York compressor, but recently switched the accessories over to a newer serpentine belt set up from a 90 model truck. The A/C was working with the York so I just installed the "new/ junk yard" compressor in its place and replaced the drier. I pulled vacuum for around 45 minutes and let it hold for over an hour, then charged with R134a. It never would blow cold out the vents, it would blow semi-cool but that's it. At 1200 rpms the pressures are 50 on the low side and 175 on the high side and when I disengage the compressor clutch the pressures equalize within 2 seconds (when the York was installed it took around 7 minutes for the pressures to equalize). I also noted that the expansion valve is cold to the touch at the inlet of the evaporator, but the outlet of the evaporator isn't cold at all. Also when the York was installed the low side hose fitting on the compressor would be cool and get condensation on it, with the FS10 the low side fitting doesn't anymore.

I'm confused on whether its a compressor problem or expansion valve problem.

Thanks,

bohica2xo on Thu June 23, 2011 12:30 PM User is offline

How much refrigerant is in the system? How much oil?

At 90f & 1200 RPM engine, I would expect high side pressures over 200 psi with the oem tube & fin condensor & a properly working fan clutch.

Could be a tired compressor - you have no history on it. Or you could be undercharged.

A TXV failure would have different symptoms.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jvsutton on Thu June 23, 2011 2:35 PM User is offlineView users profile

I don't know exactly how much is in there. It's probably a little under 2 lbs cause I put about 2 and 1/2 cans in it trying to get it cold, but it never would blow cold. It has 9 oz of ester oil in it, that's the amount I was told to put in it on the ford trucks forum.

You mentioning the fan clutch, I don't have a fan clutch I've upgraded with the Tauras fan and I have it hooked up to kick on high when the AC is turned on. Sorry I forgot to mention that originally.

Thanks,

bohica2xo on Thu June 23, 2011 2:54 PM User is offline

You are undercharged. That truck was probably a 52 ounce charge on R12, should have a sticker someplace.

You will see high pressures with 134a in the OEM tube & fin condensor. The fan downgrade will not make it any better.

Depending on how much performance you expect, it may be necessary to upgrade the condensor for 134a.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jvsutton on Thu June 23, 2011 3:17 PM User is offlineView users profile

Yes it does have a sticker on the core support, I can't remember exactly what the amount is. I'll look when I get home and pick up a couple more cans of r134. I was looking in the JY the other day at newer condensors just in case I upgrade. 99 Lincolns have HUGE condensors and I can always pick up the correct fittings to hook it up.

Thanks, I'll let you know what I find out when I add some to it.

jvsutton on Tue July 05, 2011 10:22 AM User is offlineView users profile

Ok, I had a chance to add some 134 to it.

The temp was about 95-98^ outside. I had the truck running at 1500 rpms and added most of another can. The low side reading was 55-60 (which still seems too high) and the high side was 225-250. The air coming out of the vents felt a little cool, but still not cold. Just like before the side of the expansion valve hooked to the evaporator was cold, but nothing else was.

The sticker on the core support said 2.75 lbs of R12 which is 44 ounces. 80% of that would be 35.2 ounces, so right at 3 - 12 ounce cans of 134.

Are there any tests to preform on the condenser to see if I can get the air to blow colder in the truck to know for sure if it is going to be necessary to upgrade it.

I know I mentioned I have the Taurus electric fan upgrade done to my truck and I have the high setting hooked up to kick on when the AC is turned on, but I do have another small fan made specifically for a condenser that I can hook up if you think the condenser needs a fan blowing right on it.

Thanks,


bohica2xo on Tue July 05, 2011 12:41 PM User is offline

Mist some water on the condensor, while watching the pressures. If you see the high side drop substantially then you have a condensing problem.

You should have a sightglass on the receiver. What do you see in there @ 1500 engine rpm?

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jvsutton on Tue July 05, 2011 1:04 PM User is offlineView users profile

I don't think it has a sight glass on it, it's an aftermarket one from Autozone. I never paid much attention to it since everything I read said sight glass doesn't matter with r134. I'll look at it when I run home for lunch, and let you know. I'll mist it with the hose too and let you know.

Thanks,

I read on another thread about taking the bulb for the TXV and putting it in cold water and hot water and see what the pressures do, would that be a test a try too?

jvsutton on Tue July 05, 2011 2:21 PM User is offlineView users profile

Ok, here's what I got from lunch,

There is no sight glass on the drier.

The outside temp was 81^

Idling at 1500 the low side was about 43 and the high side was about 150. It was blowing cooler than the other day when it was so much hotter outside.

Running water on the condenser brought the high side down to about 125. As soon as I lowered the idle back to 650 the low side went to around 55 and the high didn't seem to change much. And it didn't feel as cool as when the idle was up.

jvsutton on Wed July 06, 2011 12:22 AM User is offlineView users profile

Ok, here's some more information. When I got home this afternoon the outside temp was 90^. I took the bulb of the TXV off the outlet of the evaporator and put it in a glass of cold ice water. The low side dropped to about 35 and the high side stayed around 150, but the air out the vents didn't feel any colder. I also did another test that I read about in another thread by trying to pinch off the suction line with some vice grips for a few seconds to see if the compressor would suck down to a vacuum and I didn't, the pressure did drop but not very far. I think I need to see about getting another compressor.

jvsutton on Sat August 20, 2011 12:38 PM User is offlineView users profile

Ok just an update, it was the compressor. I got a new (used) compressor and another new drier changed them out and charged it up and today it was 90^ and I'm getting about 58^ out the vents. Definitely cool enough for me! Thanks for all the help!!

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