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Question DetailsAsked on 3/27/2017

Should an AC technician be able to tell when a coil is bad

AC stop working. AC guy came out and recharged the freon. By the next evening the AC wasn't working again. He came back out and said the coil needed replaced. I was charged a second time for freon when the new coil was installed. My question is shouldn't he have been able to test the coil on the first visit to determine if it would hold a charge?

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1 Answer


If he tests it before recharging yes, but since they get paid for the visit plus for the gas (and many REALLY overcharge for the refrigerant gas, by 5-10 times what they pay for it sometimes) the incentive on a non-functioning A/C is to just refill it and see if that cures it - without diagnosing the problem.

If it is down a pound or two (out of commonly around 5-10 pounds of gas in a system), especially if it has not been topped up in many years, they may assume it is just very slow joint/connection leakage and top it up - or if they suspect a not readily detectible leak (say it loses a pound or two every few months to a year to a slow leak) they may put a dye in the system which shows as a bright (or ultraviolet) "bloom," or mist at the leak point, to be seen next time they come, to identify the leak point. [A very small leak can take a week to month or more to show a dye marker at the leak point] so commonly the system is dye injected and then the gas brought back up to propoer amount to get the system up and running till the leak point shows up as dye marking.

But if the system was basically bled down, as yours evidently was if it leaked down again in a day, then before putting gas into it he should have checked the pressure, seen it was very low or zilch, and commenced testing for a leak - usually initially with ntirogen gas or air if the system was basically leaked out, using audible, ultrasonic, laser thermometer, or infrared camera methods to detect the leak point and fix it BEFORE recharging the system.

Just pumping it back full of refrigerant without first finding the source of any significant leak is unprofessional and a waste of your money, and technically illegal as well. [It is illegal to intentionally or knowlingly discharge the refrigerant into the air (with specified limited quantity exception allowed during maintenance and testing and making connections and such), but certainly putting gas into a known-to-be-leaking system falls in the category or knowing or willful discharge.]

Question- when he replaced the coil, did he test it first to see if the coil was leaking, and not the tubing to/from it or some connection or other component ? (Though if it has not since leaked down in a couple of days after the replacement, unless it was leaking right at the coil connection, then probably the coil was the problem).

A LARGE percentage of the coils sent back to manufacturer as defective turn out to be fine, and the leak was elsewhere. When I took the Carrier HVAC factory commercial certification course they grabbed a pallet of returned heat exchangers and A/C coils that had come in from all over (only one or two from any one vendor) as leaking and we tested them - over half had no detectable leakage or damage.

Hopefully if this is a newer unit (less than 10 years say) hopefully he checked if the coil was under warranty, because if it was the coil itself (though commonly NOT the labor or the gas) should have been free.

Personally, assuming you asked him to repair the problem (rather than say specifically saying you wanted the unit topped up with gas), I would call his first visit a fail land tell him I was deducting that payment from his second billl because he failed to diagnose the problem the first time around.

Answered 3 years ago by LCD

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