Ford F-150 A/C problem

I'm trying to locate the orafice tube to install a new one, beleive the existing one is plugged, have good press. untill the compressor kicks in the press. drops to zero and compressor shuts down
for a few seconds then back on.
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Dlhhedge814 wrote:

Your problem is caused by low refrigerant charge. If you had a proper gauge set that would read high and low side pressures, you would see the high side start to climb while the low side drops. The usual culprits for leaks are any of the spring lock couplings, and the compressor shaft seal or body seals.Look for oily residue around all of the connections, the dirty ones are leaking. Same with the compressor, oil behind the pulley=shaft seal, oil on the body=housing seals. If the truck is a late 80's-early90's vintage another problem is rust on the condenser tubes. Look for the tube coming out of the lower right side of the condenser that runs up to the connector (look through the grille, passenger side). If there is flaky rust on the tube, a new condenser is in order. There could be leaks in other places, but these are the most common.
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I have a set of guages that read high and low side, I've checked for all the leaks already, and just in case tried to give it a charge, but it would not take any. That is the reason I beleive it is the orafice tube, but can't seem to find it. as you suggested I checked for the rust but can find none. I really need to find the orafice tube to change it anyway, can you help me locate it, I've checked the sevice manual but, it gives me no location for it or no instructions how to go about changing it.
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Dlhhedge814 wrote:

If you have the gauges, what are your readings? Most importantly, what is the static (engine off) pressure reading at the low pressure port at say, 80 F. ambient temp?
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I don't have that info as of yet have to hook up the guages and check it once again. Thank you for the info.
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A plugged orifice will cause high side too high, lowside too low. It is has to be in the small line going into the cab. On Fords it is sometimes in the line itself so you have to replace the line. Or it could be very near where that line goes into the cab at the firewall.
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I've had the system serviced about 5 years ago and they told me they changed the O-tube, maybe they handed me a line of BULL, think so? The service manual m entions nothing about changing the O-tube, just gives a general location.
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See
http://www.ford-trucks.com/forums/showthread.php?t 0545 http://cv6.fakeleg.com/techfiles/ac.system.general.servicing.pdf http://www.ford-trucks.com/forums/showthread.php?p 93464#post1993464
Ed
Dlhhedge814 wrote:

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Thanks will check out those sites!!!!
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Thanks will check out those sites!!!!
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Dlhhedge814 wrote:

The orifice tube is, I think, part of the liquid line and not replacable. Your problem is not a plugged orifice. Jumper the cycling switch on the accumulator while charging and place the refrigerant can in WARM water. If the gauge is reading the low side pressure, the system will pull the refrigerant in. Always charge through the Low side port, NEVER the high side. When fully charged the inlet and outlet of the evaporator should be about the same temp and the high side pressure should be about 2.5 times the ambient temperature. If the high side ever goes up over about 275 there is a problem, very likely a bad fan clutch or air in the system. If you have opened the system looking for the o-tube, you MUST pull it into a vacuum before charging. It won't cool and the high side pressure will be WAY high and could damage the compressor.
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Thanks for the info, I guess thats why the service manual dose not refer to how to change the O-tube, as a last resort I was going to try vacuuming out the system and giving it a fresh charge, it had been working fine untill about 2 weeks ago. I've tried jumping the low press. switch and adding gas but that didn't work it just would not take any, like the system was full but the guages read zero press on the low side with the compressor running.
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On Tue, 14 Jun 2005 22:47:00 -0400, "Dlhhedge814"

If the guages actually showed "0" pressure on the low side with the compressor running, then, you have either a bad clutch cycling switch or, your guages are not correct for some reason. Continued operation of the compressor at "0" pressure on the low side will destroy it because the lubricant is not being circulated. If the compressor has operated in this manner, the entire system will need to be gone thru to clean out the debris.
Good luck Lugnut
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