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Question DetailsAsked on 7/26/2017

AC reversing valve capillary tube blown?

My AC stopped working, and the tech diagnosed the problem as a leak in the reversing valve. They repaired the leak, and refilled the unit with 11 pounds of coolant. 2 months later the compressor blew.
I've spoken to a couple other techs that seem to think that situation was handled incorrectly. I've been told that at the very least the reversing valve should have been replaced, and that type of issue is often indicative of other system problems. I also found out that our system was only a 10.6 pound system, but they put in 11 pounds.
My question is if repairing a leak in the reversing valve, and not looking for other issues is a reasonable course of action? Also, can overfilling by .4 pounds cause compressor problems?

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Voted Best Answer

Obviously it cannot be diagnosed from thousands of miles away - but unless the leak was just a leaking fitting/tubing joint on the TXV or a matter of cleaning it out with solvent because it was getting gummed up, I agree with the other comment - generally better to just replace it but the tech may have been trying to do you a favor and keep the cost down for you. The part itself is from about $50-300 but typically in the $150-250 billout range. Oops - you said REVERSING valve, not a TXV, so you have a heat pump, not an A/C - so more like $50-500 cost and typical HVAC company billout probably around $250-350 range for the part - plus maybe an hour labor for the replacement once he was there.

And while the valve was out (so gas had been pumped out) the filter/drier should have been checked for contamination or sludging or scorched lubricant (which circulates with the refrigerant), and at least the filter cartridge (or the entire filter/drier if a unitized type rather than cartridge type) replaced. If it was heavily sludged or showed scorching THEN I would have recommended further investigation into the compressor condition - though these days with the sealed units basically all you can do with the compressor to check it is listen for odd sounds, check if the housing is running unusually hot, and check that is is coming up to proper pressure. And flushing out the entire system if sludgy or scorched, which is another coupel or few hundred $.

And yes, a gummed up or sticking TXV or reversing valve is commonly an indication of something else bad going on in the system - commonly a leak causing the pressure and gas flow in the system to drop off, which reduces lubricant circulation, hence can cause compressor overheating and failure. A failed compressor then brings up the issue of repair or replace, especially with older systems, because it is pretty pricey to replace that - sometimes $1000 range but on many models more into the $2000's.

As for the 11 pounds versus 10.6 - firstly, many HVAC firms bill out by the even pound not decimal pounds, so that could explain it. Also, the "rated capacity" of the unit is for the standard unit and typically 15 or 25' of lineset tubing of a certain size - change that lineset length or diameter (and commonly if getting longish you have to upsize the diameter to reduce friction losses) and it can change the amount of needed gas to fill the system by a pound per perhaps 10-20' of tubing length or upsizing - so a somewhat longer or larger tubing run to the evaporator coil for instance can easily make a pound or few difference. If the coil has been changed out in the past with an aftermarket coil that can also change the required volume of gas by a pound or two, so that small amount difference, whether roundoff or variation from the nameplate capacity, would not concern me at all.

[When filling they system, at least when done right, the amount of gas put in is controlled by the stable operating pressures on the "high" and "low" (or pressure and vacuum) sides of the system - so the amount of gas is adjusted to get the operating pressure correct for the system and the ambient temperature when it is running, not to a particular amount of gas in the system.]

So - bottom line - not knowing what exactly he "fixed" on the valve or whether he checked for sludging or scorching, but as the issue is stated I would not say this was necessarily a case of it being done "wrong". If the original service call was due to lack of cooling or noisy/clunking compressor (especially the latter) or freezing up of the coil (all of which can be caused by low gas pressure), then it is possible the compressor had already beenn compromised and just eventually failed a couple of months later. Regretable, but a risk you run when you repair an appliance or car or whatever type of system (especially if an older one - 10+ years old) rather than repair it - while it may give you many more years of service and be well worth the repair, other times you just get a cascade of failures with one component after another going out, so it can be a tough decision to make.

BTW - you can find a number of previous questions about repairing versus replacing an A/C (or heat pump - essentially same issue except you are looking at heating and cooling both) in the Home > HVAC link under Browse Projects, at lower left.

Answered 3 years ago by LCD

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