One of my A/C units was struggling to keep the temp. down to 85 three weeks ago. The pipe outside was slightly frosted so I already knew the unit was a little low of refrigerant. Called repair company to check unit out. The service technician said the unit was 2 lbs. low on refrigerant. After three more days of the unit struggling, I called for them to please check the unit again for me. Two different technicians happened to be sent out. At this time, there was no sings of any frost on the pipes. The techs told my wife that the unit has a leak and we would need to replace the unit if it continued not cooling properly. The techs also said they put an additional 3 lbs. of refrigerant in the system. They also quoted us total replacement for $5,892.00. They put in an order for a new unit.

This did not make any since to me. Next, I started monitoring the thermostat. every time the thermostat showed the unit was cooling it down a little I would lower the temp setting. Instantly the current temp. reading on the thermostat would go up a degree. Well, I put two additional temp. readers next to the thermostat and both of them said the current temp was 4 degrees lower than the thermostat.

So, I decided a new thermostat only cost around $38.00 and I replaced it. To my surprise, the unit started cooling immediately and has been for the last 20 days. I would bet that the on the second service call, the unit did not need or take anymore refrigerant. I did call the company and told them the unit started working so they could cancel the new unit ordered. I failed to mention to them that I put a new thermostat on which fixed it.

So, is there a tester for thermostats? I have never seen one tested.

  • Technically, it is illegal to connect a set of gauges to a system in the US unless one has an EPA license to do so. Also, it requires a bit of training to be able to connect a set of gauges without introducing air into a system. Please see my answer below regarding your questions.
    – user39367
    Aug 29, 2015 at 23:45
  • 1
    Chris could you please give the Code or URL stating that it is illegal for anyone, other then a EPA licensed person, to connect a set of gauges to there own HVAC unit, I have never heard of this. Purchase Freon yes check the system with gauges no.
    – WarLoki
    Aug 30, 2015 at 0:33
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    From EPA Section 608, "Technician Certification": EPA has established a technician certification program for persons ("technicians") who perform maintenance, service, repair, or disposal that could be reasonably expected to release refrigerants into the atmosphere. The definition of "technician" specifically includes and excludes certain activities as follows: Included: attaching and detaching hoses and gauges to and from the appliance to measure pressure within the appliance;...
    – user39367
    Aug 30, 2015 at 1:16
  • Depending on how one reads a separate section of EPA section 608, the above passage may only apply to CFC and HCFC refrigerants, but that is not completely clear.
    – user39367
    Aug 30, 2015 at 1:18
  • @Tester101: My guess is that this question does apply to an R22 system, but that is unknown. A qualified technician is supposed to identify and repair leaks. No-one said anything about recommending "countless pounds" of refrigerant be leaked into the atmosphere, It is currently the case that a technician is not required to fix small leaks in small systems under the law. It is poor practice not to fix leaks. My opinion is that it is not good to recommend a homeowner attach his own gauges unless he has some training and awareness of the law. Your opinion differs from mine.
    – user39367
    Aug 30, 2015 at 16:08

1 Answer 1


It is service call experiences like these that give HVAC guys a bad reputation.

Many residential systems take between 8-13 pounds of refrigerant total. It is extremely doubtful that you lost 3 lbs of charge in 3 days, so either the first technician charged the system incorrectly (left it undercharged), or the second technicians charged it incorrectly (left it overcharged), or they both charged it incorrectly. If they actually put a combined 5 lbs of refrigerant in the system, then odds are pretty good that your system is now overcharged. If so, that will hurt system performance and, depending on the type of metering device your system has, being overcharged could severely shorten the life of the compressor. Secondly, the mere existence of a leak is not a valid reason for installing a whole new system. If the leak occurred because the evaporator coil is corroded to death, okay maybe, but if there is a simple pin hole or leaking fitting then, no, that is not a valid reason for a new system. Personally, I would not invite these guys back. Sorry to be the bearer of bad news.

To answer your last question, I am not aware of any tester specifically for thermostats. Usually some temperature observations and a few quick checks with a volt meter will tell a technician if the thermostat is the underlying cause of a problem or not, so no tester is really needed. Also, with the introduction of advanced digital and wireless technology into the area of thermostats the variety of complex options has exploded.

  • Thanks for the info Chris, My wife thought I was crazy not to believe three technicians. And my wife knows them. They are on my no call list now. Aug 30, 2015 at 2:45

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