91 f150 a/c problem....
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New User
Joined: Mar 2010
Posts: 16
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From: Harrells, North Carolina
91 f150 a/c problem....
first off. my ac hasnt worked right since ive had my truck (4 years) it had been converted to 134a (xh7 accumulator, compressor works compressor, fitting adapters). 80 degrees vent temp. at (95degree ambient) I want to convert it back to r12 for better performance at stop and go traffic So i evacuated the system, flushed it, vaccumed it down (it held vaccum overnight) removed the compressor, drained it, and filled with 8oz of mineral oil 500 and started to charge it with r12. after i put 2 12 ounce cans in it the low side pressure was around 70psig. the ccumulator was not cold at all but the line from the compressor to the condenser was extremly hot and the vent temp was just barely 5degrees colder than ambient. so i evacuated the system and removed the accumulator, i cut the bottom off of it with a sawzaw and found the little silica bbs in a bag witch was tore (some were in the bag, some were not, and more oil. I know I need to replace the accumulator. but would cause the restriction, orfice tube?, expansion valve?. any feedback is appreciated.
P.S. compressor does work...
P.S. compressor does work...
Fleet Owner
Joined: Oct 2005
Posts: 20,785
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From: Kentucky
When you removed the accumulator you should have seen the orifice tube in the inlet pipe fitting. Take a look at it. If it is coated in debris you know what the problem is.
A high reading on the low side and high vent temperatures does indicate more of a compressor problem. Many R-134a conversions result in failure due to residual oil traces that contain chlorine from the old refrigerant. Chlorine and PAG/Ester oil do not play well together. Your compressor may work, but not very well. The orifice tube will give a good visual indication if the system is contaminated with debris from the compressor coming apart.
A high reading on the low side and high vent temperatures does indicate more of a compressor problem. Many R-134a conversions result in failure due to residual oil traces that contain chlorine from the old refrigerant. Chlorine and PAG/Ester oil do not play well together. Your compressor may work, but not very well. The orifice tube will give a good visual indication if the system is contaminated with debris from the compressor coming apart.
Lead Driver
Joined: Feb 2002
Posts: 7,957
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From: Greater Austin, Texas
I'm gonna disagree with rla here, the orifice tube is inside the inlet to the evaporator core where the liquid line from the condensor connects with one of those spring fittings. You need a special tool to release that, it's kinda like the ones you use on later model fuel filters.
But if you had a restriction at your orifice tube, you would show vacuum on the low side since the fitting for that is after the orifice tube.
Did you not have a complete set of gauges hooked up? It would be very helpful to know what your high side reading was.
But if you had a restriction at your orifice tube, you would show vacuum on the low side since the fitting for that is after the orifice tube.
Did you not have a complete set of gauges hooked up? It would be very helpful to know what your high side reading was.
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New User
Joined: Mar 2010
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From: Harrells, North Carolina
Yup. Orfice tube was clogged. Replaced it for 2bucks. But what would cause so much debris to build up on it?. I'm assuming it was like that before I started messing with it. Should I go back to r12 or stick with 134a?
Lead Driver
Joined: Feb 2002
Posts: 7,957
Likes: 592
From: Greater Austin, Texas
Yup. Orfice tube was clogged. Replaced it for 2bucks. But what would cause so much debris to build up on it?.
But I still say a clogged orifice tube is not going to cause your low-side pressure to be 70. You were measuring at the fitting on the accumulator, right?
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