Quote:
Originally Posted by Sunroof
About 8 years ago I replaced the hoses and updated the York compressor with a Denso.
Of course the darn thing was blowing warm air as i t always has and although I did remove and clean the front and rear condensers and added a new drier before recharging nothing changed!
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Interesting post Bob. And great to hear you have working AC.
Maybe you did have a problem expansion valve (TEV for less typing; or TXV or whatever floats the boat).
But, I'd have to say that if every 911 or 930, say from 1966 to 1989 with factory ac, that was not blowing cold had its TEV replaced and blew cold ac, AND the conclusion was the TEV was the issue, well, that would be interesting.
Normally you can diagnose an issue "at" the TEV.
Closed or blocked valve = low low side pressure.
Open valve = normal high side pressure but higher low side pressure.
However, those 2 simple statements above are not enough to convict the valve to retirement.
A "closed or blocked valve" means the evaporator core is starving for refrigerant, running too 'lean': the diaphragm or circuit in the valve that throttles the valve needle to its seat is not working normally. This could be a mechanical failure in the valve mechanism or it could be debris. Debris could be blockage before the valve inlet (ice, drier desiccant, "oil snot" which is old congealed mineral oil, old ac hose particles or other foreign matter). Ice or moisture can develop before the entrance to valve or inside the valve .... even if you have replaced the drier and pulled a vacuum. "Pulled a vacuum" means although you connected a manifold gauge set and needle on the low side gauge says you are near 30" inHg but what has happened is all the moisture never left the system, it froze inside (yup it happens; you can turn that liquid or gaseous H2O into a solid (freeze) before it has timed to vapor out). This is why on long refrigerant runs (lots of hose) you flush out the ambient gases (air) using nitrogen or refrigerant. Many times these systems are evacuated and charged and the first time results are not good. However after repeated refrigerant recovery, evacuation and charging the "TEV issues" disappear.
An "open valve" means the evaporator core is engulfed with refrigerant, running too 'rich'. Again it could be a mechanical failure or debris in the valve and seat. And, many times repeated repeated refrigerant recovery, evacuation and charging the "TEV issues" disappear as well.
All of this is not to say you did or did not have a failed TEV. Simply, its better to diagnose the issues than throw parts at the problem.
Enjoy your cool summer ride.