A/C Evaporator Coils Leaking?

Depending on size of leak, it can be easy of very difficult to find.If it is on an inner layer of the evap coil, it can be hard to detect, especially if it is a slow leak, which i presume it is.The original inspector said it was low.If it was a large leak, it would have been completely gone.They sell freon with a dye in it for leak detection, but you may not be able to buy it without EPA certification.Also they sell a adapter for using a propane torch for finding leaks.It sucks in air via a pitot tube, and the flame changes color if freon is present..

Does that also work with non freon gas in AC? At least here in Germany, Freon is a big NO NO!!!

I used to use a pressure blow lamp, running on Methylated spirit to look for Freon leaks on HM ships over 40 years ago.......even very small Freon leaks changed the flame color dramatically.......

Hello Andy:

I'm not even sure if you can buy the old halide leak detectors anymore. They were very effective and you definitely got a color change. I would have to look at my EPA requirement book, before I quoted an exact percentage of refrigerant that can be mixed with nitrogen when checking for leaks. I'm also not sure whether the new refrigerants will cause a similar color change using a propane leak detector.

I do know they fell out of favor after a few incidents of servicemen concentrating on looking for the leak, and setting the detector down and starting a fire.

The the latest generations of electronic leak detectors function very well, unfortunately they are also relatively expensive A lot more expensive than the $20.00 I used to pay for my halide leak detectors, I just checked and the halide detectors will only work with chlorinated refrigerants.

Many thanks for the good update......I am simply getting too long in the tooth!!! Everything is being superceded....

Dear Guest,

Everyone gives you good idea on procedures and way how to find the leak. However my concerns is; considering you find the leak yourself, successfully welded it yourself, are you capable to run the unit in the correct way without making more damage like putting in the refrigerant with proper pressure both high side and low side? are you not burning the compressor? are you not going to make the situation becomes more worst? if your objective is to save money but the unit repaired properly, hire the proper technician to do the proper job, for me that is the best and easy way to do. also trust the technician you are most welcome to watch them while doing the job to ensure that they are not cheating you. at the same time from there you are learning and then maybe next time you will be have better idea if you want to do it yourself.

kind regards

Roman

I think the OP just wants to find the leak and get it repaired himself, the rest he will let a qualified person do. That way he possibly saves on buying new coils........

That was my take anyway......

you can use halide torch or simple soap solution to find the refrigerant leak in a cooling coil. Is it a FCU type or VRV system?? . If the system does not have enough refrigerant system may rum but with more power consumption. Retrofitting Freon with HFCs need full understanding of the system. Please consult HVAC engineer as per the codes.

I recently bought a house and had the same issue. A/C inspectors claimed the coils were leaking and the whole unit needed replacement (big bucks). One day while weeding the area around the outside unit I detected a slight hissing noise. Upon further investigation I determined that the Schrader valve where the A/C inspectors tap in to check the refridgerant pressure had developed a leak. Five dollars later I had installed a new valve, had the system recharged, and it's worked like a top ever since.

So, check your Schrader valves for leaks as the springs and seals in them can wear out over time.

Thanks to everyone for all the good advice -- a lot of it over my head.

YWROADRUNNER - I very much appreciate the level of detail you offer... and Andy, you are right. I wasn't intending on repairing this myself. I was just curious if anybody had experience where it turned out the coils weren't really the problem. So Old Submarine Sailor's answer confirms my fear that if you are low or have no refrigerant in the system it has to be the coils. Maybe in most cases it turns out that way, but I suspect more often than one would hope replacing the coils is just a way to generate a job with more labor charges -- sort of like a lot of surgeries that really aren't necessary.

In the end, I may just have a couple of more technicians look at it and hope someone might investigate it more thoroughly than it has appeared so far. I mean, the last guy didn't do ANY leak checking he just assumed the first guy had gotten it right and when he saw NO pressure in the lines he just echoed that the coils probably need to be replaced. Most people work too hard for their money to have a cavalier inspection done. I have another, older, technician scheduled to look at it this weekend.

Thanks to all. I'm in the middle of trying to move, get my car repaired to do the move and still keep my job. But I intend to repost here after the dust settles to let you guys know what I find out.

I'm sorry if my comment mislead you. What I was trying to say is, it wasn't the coils leaking at all on my unit. It was the Schrader valve that was leaking and allowed the refrigerant to escape. So instead of paying the A/C company big bucks to replace the coils, it only cost me $5 plus the amount of freon required to recharge the unit.

You're best bet is to have someone competent do a thorough leak check of the system before you drop the big bucks on new coils. It could save you moeny in the long run.

Oh, no. Your comments didn't mislead me in the least. What I was saying was it confirmed the fears I had (which prompted my OP) of NOT getting a thorough leak test done... in other words, I want someone who will make sure it isn't that $5 Schrader valve. :)

Any qualified technician carries an electronic leak detector now days. On R-22, which most older systems use, an electronic will find a very small leak quickly. The law in the US is that if the system has NO refrigerant in it, a small amount of R-22 can be put in, then pressurized with nitrogen. All competent technicians carry nitrogen. If you even suspect a coil leak, after the system is pressurized for about 5 minutes, put the leak detector by the condensate drain. Be sure there is not water in the drain trap, cut the drain line ahead of the trap if necessary. the system needs to be OFF during all of these tests. If there is a coil leak, since refrigerant is heavier than air, the leak detector will sound off when near the drain opening. When the leak is located, the nitrogen/R-22 mix can legally be released to depressurize the system to do the repairs.

As for the schrader valves leaking, as service manager for a refrigeration company, when I read that on a work order my mind sees "I (the tech on the job) didn't feel like doing a thorough leak check, so that is what I'm going to say. A second call is coming." (Obviously in rare cases, like Old Sub's, there are exceptions. but if the schrader is capped, as it should be, if can't leak.)

All that said, refrigerant leaks, even big ones, can be hard to find.

Coils that have leaks on the return bends are usually not worth fixing, as they tend to spring more leaks and are time consuming (read expensive) to fix. -- JHF

schrader valves can leak when the o-ring in the cap has a cut in it. It appeared that the last tech to service the unit had a leaky valve and torqued down the cap to stop the leak. It must have worked for a little while, but the cut/crushed o-ring in the cap eventually allowed the freon to leak out. I just happened to be pulling up a weed with my head right beside the cap when I heard the leak.

Agreed! But, most of the time when the tech say "schrader valve" you can plan on a re-call to find the real leak. I did not mean to say otherwise in your case. I'm glad yours was an easy fix and I hope guests is too. -- JHF

Thanks for the reply Circuit Breaker.

Hi: Here are some thought from an old refrigeration service man.

I am a little surprised both individuals identified the evaporator coil was leaking when they did not appear to do a proper refrigerant leak test. There are many other areas in a refrigeration circuit that can develop leaks.

In-order to perform a proper leak test one must first pressurize the complete refrigeration system with the same refrigerant that was initially used. Once the system is pressurized you will need to check the total system with an electronic refrigerant leak detector. Once the leak has been identified only then can you make an assessment to the extent of the repairs needed. This is a task that requires the skills of a qualified refrigeration service mechanic.

I trust these thoughts will provide some guidance to the solution to your question.

if the servicemen did not take time to look at it or test it there is no way they knew it is the coil that is leaking and they were just trying to get you to buy a new coil or better yet a whole new a/c system IMO. They assume it is the coil because it is the most likely place for a leak. They also usually tell you that it has to be replaced and can not be repaired because their rate is so damn high and removing and properly repairing a coil can be a time consuming job. If you want to be sure get an a/c man to fill the system with inert gas and with a soapy water spray mix check the coil, line set and everything else in the unit and the air handler that could leak. It could be that you have a leak at a solider joint in the line set only. The replacement parts for an a/c unit over a few years old tend to be very expensive I think the a/c manufacturers set the price on them high hoping to get you to just buy a whole new unit. I have a heat pump a/c unit leaking somewhere at the moment and I will have to do this check myself before next summer. Checking the system can be a hard job in itself unless you get lucky and find the leak right off but it can also save you a good bit money if it turns out to be a repairable leak.

Sorry I didn't post back with an update on my situation for all who were kind enough to post responses to my question.

I had a third A/C man (recommended by an older construction worker) who has 40 years experience look at my system.

He showed up with a leak detector, gauges, etc. First he went up in the attic and did a visual check for oil in the overflow pan. He said if there was a leak in the evaporator coils it would probably be small, since one usually finds evidence in the form of oil in the overflow pan and he didn't see any. Next we turned on the unit and he went outside with his electronic detector and passed it around above the fan outside. He was detecting a leak. He noted that "someone" had left one of the valve "caps" loose. I asked him about these valves and if he thought that was where the leak was. He checked what looked like an internal stem or something that he tried tightening with a small screwdriver type wrench (I didn't get a good look at it.) It was loose, also. He said, "I wonder why "he" (meaning the person who did the first inspection) would leave these loose... unless he wanted them to leak?" He checked all the fittings for tightness and then put a partial charge on the system. We then went back up in the attic and checked for a leak with his detector. There were a couple of beeps but overall no alarms. He then checked at a couple of the registers in the house. Still no real beeps. Then we went back outside and he charged the system to normal and checked around the outside, around the valves/fittings and in the air stream from the fan over the compressor/coil assembly. No real leaks detected. His opinion: it would last several months at least and maybe longer. The few beeps may or may not have been a very small leak. He wouldn't commit. But he said he thought it was going to work. He went back in and checked the air temp. at a couple of the registers. His thermometer showed a range of 55-59 deg. F. Pretty good, I think.

I have run the A/C system now several times over the last couple of weeks and all seems to be well so far.

I know that some who posted here are A/C technicians and I don't want to offend anyone, but I have to conclude that the first inspector/technician either intentionally left the system in a "leaking" state or was careless in checking for these loose connections in the first place. At the end of his inspection he had quote a price of $1,300 to replace the evaporator coils. The second technician who also said he thought the coils needed replacing never checked for a leak, although he did go up in the attic to look at the coils; although I don't remember that he looked in the overflow pan for oil. He only looked at the pipe connection at the coil entry. He quoted $650 to replace the coils.

This third technician charged me $45 for the service call and $100 for 5 lbs. of coolant, for a total of $145.

Since we won't be having consistently hot weather now until next spring I won't know if this is going to last. But it will be a good test to have the system "sit" for several months and then see what happens the next time we really need to cool the house. (Although, in this part of the country -- central Texas -- we can have hot days at odd intervals throughout the "winter".) We'll see.

Thanks again to all who posted.

"But it will be a good test to have the system "sit" for several months and then see what happens the next time we really need to cool the house."

Try to keep track if it seems to leak worse when the system is of or on. Low side leaks (indoor coil and the large pipe) are worse when the system is not running, Hi side (Outdoor coil and small pipe) leak worse when running. -- JHF

I know on cars that one needs to run the AC for at least 10 minutes a week to keep all seals lubricated and sealed, even in winter. Would that not also be a good idea on a home system?

Hello Andy

Something I had entirely disregarded was running my automotive air conditioning during winter months makes great sense.

As far as residential air conditioning units the compressors are hermetically sealed so there's no seals really to worry about. One item I like to see cycled every now and again is the reversing valve in heat pumps, but generally that pretty much takes care of itself as long as the units being used periodically.

Not so necessary on fixed base equipment. Cars use a belt driven compressor, thus a seal that can dry out and start leaking. Small fixed base equipment uses a sealed motor-compressor, no seal so no worry about leaks. There is, however a small heater on a lot of A/C compressors to keep liquid refrigerant from pooling in the compressor crankcase. If one turns off the power to the outside unit, it is recommended that power be turned on for 24 hours to drive any liquid refrigerant out of the oil before starting the condensing unit. -- JHF

Dear Guest,

I just copy paste what I replied on your post and highlighted /underlined portioned that seems to be related to the point that your problem was been solved, however I am not a Technician but the word "trust" for the first technician who do the checking is not applicable, but for sure to the last one yes, good luck and hoping your air-con will last. Thanks for who ever gives me the 1 GA vote on my first reply.

"Everyone gives you good idea on procedures and way how to find the leak. However my concerns is; considering you find the leak yourself, successfully welded it yourself, are you capable to run the unit in the correct way without making more damage like putting in the refrigerant with proper pressure both high side and low side? are you not burning the compressor? are you not going to make the situation becomes more worst? if your objective is to save money but the unit repaired properly, hire the proper technician to do the proper job, for me that is the best and easy way to do. also trust the technician you are most welcome to watch them while doing the job to ensure that they are not cheating you. at the same time from there you are learning and then maybe next time you will be have better idea if you want to do it yourself."

kind regards

Roman

Thank you all for the great discussion and ideas. I'm keeping my fingers crossed.

when i show up to look at a unit and find it completely out of freon -

1. i'll do a quick visual check for any signs of leakage (oil stains), including inside the valve caps.

2. i'll put my vacuum pump on it. pull a quick vacuum and see if it holds.

if it does, i'll pull a deeper vac and charge it. set charge properly, check operation. if ok - call if problem recurs.

* you not having known the history on the system would have kept me from spending too much time looking for a leak that might not exist. when faced with paying for the extra time (for sure) vs. another service call (maybe) most customers (again, not knowing the history) would agree with this approach.

if it doesn't, charge with nitrogen/refrigerant and find the leak. sometimes you have to isolate the line-sets from the coils and check all individually. sometimes this, sometimes that. all leaks can be found, some are a real b*tch.

* alot of newer coils leak like sieves. older coils not so much.

* you would be suprised by the number of systems that are out of refrigerant because of people huffing it. seriously. unsupervised house, system dead, no leak found - real common.

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Good response! Since I don't do much A/C work, we don't run into the people opening a system to sniff the refrigerant, so I didn't think of that. I often try to get my techs to talk to the customer to see what they want to do when there are several approaches. I, also, think someone who jumps on the "needs this" or "that" without doing adequate checking is not being fair with the customer. Again, Good answer! -- JHF

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" zero psi ? your neighbors kids might be getting high "

i just now came up with that. kinda catchy, huh ?

seriously though, thanks for your kind words.

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