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...

 

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.

 

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.

 

I stand corrected. Jas88 has it correct. The tube leading to the input of the evaporator is where the orifice tube is located.

 

lick your a/c ****

 

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?

 

Generally it means your compressor is fixing to go out. Was the stuff it was clogged with black? These compressors regularly fail with what is known as "black death" which fills your system with a lot of crud that you can't hardly get out.

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?

 

Here is good article on your Black Death Problem:

Automotive AC Information Forum - ACKITS.COM

 

I agree with jas88 as to what is the cause of the debris on the orifice tube. The clogged tube itself is not causing the high reading on the low side pressure, it's the compressor going out.

 

Yeah I guess you would only go into suction on the low side with a restricted orifice tube if your compressor was working properly.

 

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