Recharged Dehumidifier Put Back Into Service

For the average consumer, repairing relatively low-cost home devices such as microwaves and TVs just isn’t economically viable. You can hardly blame them when the repair bill could easily be higher than the cost of just buying a new model. Luckily for folks like us, that means you can often find cheap or even free appliances on the second hand market that can be brought back online with a bit of troubleshooting and some spare parts.

Take for example the non-functional dehumidifier [HowToLou] recently came across. You probably couldn’t find a professional repair shop that would be willing to bother with one of these things if you tried, but as he shows in the video below, that doesn’t mean the DIY’er can’t run through some probable failure modes and get the unit back up and running. As a bonus, he also walks viewers through how your typical compressor-based dehumidifier operates.

The failed thermal switch.

Beyond the lack of water in the collection compartment, the first sign that something was wrong with this dehumidifier was that the compressor wasn’t running. Upon closer inspection, [HowToLou] determined that the thermal cut-off switch had failed and was stuck open. Luckily it had a visible part number so he could order a replacement, and in the meantime, all he had to do was cut the switch out of the circuit and wire up the compressor’s power directly.

Unfortunately, even with the compressor running, no water was being collected. Noticing that the evaporator coils weren’t getting very cold, [HowToLou] thought the unit might be low on refrigerant. Usually these systems aren’t meant to be recharged, but with a clever piercing tap valve, you can add a quick-connect port to the low pressure side. This particular dehumidifier happened to be filled with the same R134a used in automotive A/C systems, so a quick trip to the auto parts store got him a can of refrigerant complete with a handy pressure gauge.

After getting juiced up, [HowToLou] shows ice forming on the coils and plenty of water getting dumped into the tank. Automotive A/C refill cans usually include some substance to stop or reduce leaks in the system, so hopefully this will end up being a long-term fix. It might not be the most elaborate dehumidifier repair we’ve ever seen, but it’s certainly the most approachable. If you ever see one of these things laying on the side of the road, maybe you should pick it up and see what ails it.

39 thoughts on “Recharged Dehumidifier Put Back Into Service

  1. I come from electronics world, but when I looked into doing a few plumbing repairs, I saw a lot of “do not use quick-tap valves” – I do not remember the exact problems with them, but it boiled down to “they cause leaks long-term”. I wonder if this advice would apply here, too.

    1. Probably possible, but what’s the alternative here? Cutting the pipe and soldering in a valve seems like a lot of work for something out of the trash that may or may not even work.

      Besides if it’s out of coolant then it must have leaked out already, so seems like the tap is least of the problems.

    2. Unfortunately, “disposable” refrigerant filled devices don’t tend to include a recharge port.

      If you really wanted to do it correctly you could get a refrigerant recovery kit, suck all the refrigerant out of the system, then cut the tubing on the low pressure side, solder on the correct port fitting, purge the line (I’m not certain what that entails) then recharge. The advantage of doing it that way would be getting the opportunity to also repair the spot where the refrigerant leaked out in the first place. I reckon all the tooling for that could be gotten for around 500 bucks at horrid freight.

      Or, spend about 50 bucks to tap it and top it off, some of the recharge cans come with a stop leak so that might even solve the initial leak issue.

      Disclaimer: I’m absolutely not anysort of expert in this field, I’ve just been spending time figuring out how to appropriately discharge refrigerant so I can harvest materials from a few dead appliances I’ve got. I don’t want to vent to atmosphere because ethics, and legalities.

        1. I bought a dehumidifier from the local big box store. It lasted one year and lost it’s charge. As an HVAC/R tech I decided it was not worth fixing. Bought a second one different brand same size also made in the country of cheap crap. It died after about a year and lost its charge. At this point I was determined to fix it. I always use braze on tap valves that cost about 10 USD. Went to install the valve and the copper tubing melted like it didn’t exist. If you have tried repairing any new christmas tree lights it’s as if the wire is made out of hair. You touch it with a soldering iron and it vaporizes. This is exactly the effect i got from the copper tubing inside the unit. I have a saying that fits well here. It’s made out of chinese childrens hair. I now have a dehumidifier thats 25 years old and works like a champ. It uses R-500 so if it loses its charge I would have to use R-22 but it would still be fixable.

          1. I wanted to mention that accessing the refrigerant side of any system is against the law in the usa. I hold an E.P.A. universal type 608 card which allows me to purchase refrigerants. It is actually not legal to sell refrigerant in an auto parts store. I don’t understand why no one enforces this. Also look at the phase out dates for the refrigerants. R-134a and R-410a were supposed to be the permanent replacements. They are both phased out as of 2020. CFC moved to HFC which was supposed to be good forever. however these various treaties came out and assigned a number to the refrigerant which indicates how it affects global warming. Almost all of the new refrigerants which include R-1234YF are basically propane based.

          2. “accessing the refrigerant side of any system is against the law in the usa”

            What law are you referring to? I’m not aware of any federal limitation on what a person can do with their own personal A/C system.

            Professional service technicians do need to be licensed, but that’s a completely different situation.

            “It is actually not legal to sell refrigerant in an auto parts store. I don’t understand why no one enforces this.”

            Small “top-off” cans of supplemental refrigerant are specifically exempt from the EPA regs, and can be purchased by anyone.

          3. R1234yf is not propane based. It is a fluorinated compund which is designed to be quite unstable in the atmosphere at the price of flammability. You get the worst of both worlds: Flammable (although less than propane) and fluorinated. When it burns you get really nasty combustion products: hydrofluoric acid and the fluorine analog to phosgene.
            Of course, when it decomposes in the atmosphere it does not just vanish: It decomposes to trifluoroacetic acid which is washed out – into bodies of water and it is a quite persistent chemical. Seems to have some toxicity to water organsisms.

      1. At least in the Atlanta area, you can take your devices to a place and they will remove it for free. If you buy commercial food display cases and such, they will come to you to vent them before you scrap metal them or repair them. The bonus is they usually have a valve(s) already installed. My small Summit table top pharmaceutical frig has them too. I have not gotten far enough to see if my Harbor Freight manifold and gauges hook up to it, but, it should .

    3. I heard that also, so just now looked into it.

      He’s using a subco 3-screw bullet valve, which has a lot of positive reviews online. Everyone claims that bullet valves will leak eventually, but claim that schraeder valves *also* leak and those leak more than the bullet valves. Many people claim that the subco taps don’t leak (generally – YMMV).

      The recommended solution is to use the tap valve for diagnosis, then braze the valve onto the pipe for a permanent solution. Also, note that he had to back off the valve to open it, apparently if you close it afterwards it forms a seal independent of the o-ring.

      Also of note, they recommend polishing the pipe for a smooth surface. (Not sandpapering – scratches will be leaky. Use fine steel wool.)

      Also noted: if the refrigerant takes more than 6 months to leak out, the leak will be too small to find. The use case for these valves is to refurbish old and expensive machines such as you might find in a restaurant. If tapping and refreshing the refrigerant makes the device last for 2 more years, it’s probably worth it for a $10,000 restaurant fridge. Most devices will lose all refrigerant over many years due to microscopic leaks, so it’s reasonable to recharge them to get a few more years of usage.

      1. Two of the fridges in the kitchen I work in have those valves in them cause they came sealed from the factory. They’ve been like that for years and we maybe have to top off the refrigerant once a year if that.

          1. it’s *much* bigger. that means it has a much larger surface from which to leak, more joints, and so on. and it also means it’s worth repairing. if your 10 year old fridge has one tiny leak in its 100ft of pipe, you just buy another one. “huh, i wish that’d lasted at least 20 years” you say as you shrug your way to the store. if your 10 year old industrial cooler has one tiny leak in its 10,000ft of pipe, you put annual recharging on your todo list, and if you can get the maintenance worked out you’ll keep that thing going for 30+ years.

      2. A properly brazed and tested system is hermetically sealed and should never lose it’s charge in a lifetime. Any time a system component is replaced the system will have to be recovered and recharged so a tap valve will need to be installed. Again use a braze on valve not the tap valves. You said that if it takes more than 6 months to leak out you can’t find the leak. This simply is not true. R-22 runs 100 USD a pound right now. If you were chaging the system every six months it gets pricey. I have a 45 year old freezer at my house that has never had refigerant added and works great.

    4. Could have to do with the implementation…or, the definition of “long term”. We had one installed at work in 2009, and it still hasn’t leaked. The OCD in me kicked into high gear when I saw him installing it without even wiping off the wall texture overspray, but he purged the line and the fridge water filter takes care of the rest. I only think of it when the odd topic triggers the memory.

  2. That was a highly informative video. Short, direct, lots of information.

    (I’ve come across several scrapped dehumidifiers, now I’m wondering if I can salvage one and build a refrigeration unit or salvage the compressor for something.)

  3. They are not always a refrigerant or electronic control issue. I remember one of three in a basement in which I once lived. The unit in my living area was cycling on an off. I called Sears (seller) about getting it fixed. “Can’t be fixed – all sealed unit. Must replace it” I looked a little further. The fan was not running. The on/off cycle was due to the coil freezing because of no air flow. I determined the fan had seized. Sears: “no parts, sealed unit, have to buy a new dehumidifier” Found a local fan manufacturer – minimal parts counter hours – I could not get there. Filed the rivets that held the bearing cap. Discovered babbit sleeve bearings. Cleaned the shaft and inside of the bearing with a rag and some acetone. Put the bearing cap back on with 79¢ little sheet metal screws. 2 years later when I moved out, the dehumidifier was still running. (Similar issues with other Sears products – if they would have done repairs, they might still be in business.)

    1. Eh, corporate raiders leave no survivors. The irony is, one of the most useful remaining parts of Sears is their repair parts store online, partially for the parts, and partially for the downloadable manuals and parts diagrams for many products that Sears may have sold.

      1. And that’s the entire downfall of Sears. They listened to the old E-suite guys and didn’t shift their (once world-class) catalog shopping business online. They could have crushed Amazon while Bezos was still boxing orders in his garage.

        1. Back in the 90s there wasn’t a map that said “this way lies success” that pointed to the online world. Everyone figured it out on their own time. If you were lucky, the nerds who ran your computers started prepping the company for it in the early 90s. But if you had IBM (or other contractors) running your computers they’d sandbag your IT department in the boardroom. They’d lie and tell the board they were the only people qualified to run their systems, because they feared losing their cash cows.

          Sears had some amazing IT people sandwiched in between their mainframe types. Their POS team were true hackers who *custom-designed and manufactured their own cash registers!* But Sears was also falling victim to many other forces: being bought out by investors who didn’t know how to run stores, they just wanted to sell them for parts (literally just the Craftsman and Kenmore names); a total lack of fashion sense in their merchandising; and a steadily cratering stodgy public image. They were steered directly into into the ground by their “leaders”.

          What a waste.

      2. Your kidding about the parts right? Seeing the guts and seeing what the pieces look like and how they fit together I will go along with, but have you looked at the parts prices? They are 100% based on how much will someone spend on this before just buying a new one. And once you recover from the exorbitant parts prices they stick it to you with exorbitant shipping. They tried to hit me for $18 shipping for a part they wanted $26 for that would fit in a first class letter envelope and cost what, 60 cents to ship. I expect a nice dinner first if I am going to get f***ed that hard.

  4. The valve is only $15 on Amazon, I bought one intending to fix an RV AC. I was going to try first on a dead window unit, using propane instead, supposedly will make it colder and I guess propane is probably better if it leaks out. I have a vacuum pump and a vessel for recovery, is there a place to take it so my container can be empty again?

    1. I’ve read a few posts, I think on reddit, about people doing that, of course the comments quickly devolved into a myriad of reasons why it shouldn’t be done with arguments back and forth regrading why it was wrong. I recall at least one where the OP ended up replying saying something like “chill out, I did this 3 years ago and it’s still working great”

      As to discarding, I’m planning on talking to someone in HVAC about that, older stuff might have pretty valuable refrigerants, I’m hoping I’ll be able to find a tech to evacuate a few of my things in exchange for the refrigerant.

    2. Short answer: not recommended!

      Yes there is a place to take used refrigerant (speaking of the US) IF and only IF the “container” you have is a DOT certified refrigerant recovery tank (refilling an empty non DOT tank and traveling on the road with it is breaking 2 laws). IF you are a refrigerant licensed contractor, and if the tank is full of only 1 type of refrigerant, and you have an account at a wholesale house. You might find a friendly auto garage to take it if it is 134a or R12.
      I know Propane (R-290 refrigerant) can replace R12 but I do not know if it is compatible with the different type lubricating oil used for 134a. Also note regular propane contains a chemical odorant and often enough water to cause flash freezing at the evaporator coil/metering device. Running through a couple “refrigerant filter dryers” before putting in system may help with the moisture…
      It will not be colder by enough to be worth retrofitting, and if it already has a leak know that leaking propane can be potentially explosive under the right circumstances, which is why spark proof relays and wiring connections are used. Leaking r134a is relatively non toxic as long as it’s not displacing all the air.

      1. Forgot one thing! biggest problem with most of these things is no one cleans the air filters! The lack of airflow causes icing (resultant leaks) and burned out compressor thermal safeties. If it has not had a filter in it the fins on the coil are probably plugged. The next common issue as mentioned above is the fan.

  5. i don’t really know anything about this unfortunately, but my 15yo dehumidifier’s been short-cycling if the ambient is over 78F (i.e., about 3 weeks out of the year in my basement). it seems like the thermal cutoff on the compressor is triggering. it gets a little worse each year. i’m hesitant to blame the cutoff, though, because i happen to have tested a frequency-measurement-app on it, and i know in 7 years it has gone from 58.0Hz to 57.4Hz. if i understand correctly, it’s probably an inductive motor which varies from the 60Hz powerline in proportion to its load? so presumably there’s some sort of wear issue that is making it slow down over time? so i think it’s generating more heat and the thermal cutoff is triggering correctly.

    wish i knew something about how compressors age over time, whether this is a symptom of something relatively easy to fix. not really excited to open up the coolant loop and try to figure out how to clean or re-oil it, even though i am willing to do some brazing. i cleaned the radiators in it a couple times and i’m always struck by how much it rusts, can’t believe they used non-stainless ferrous metal on a condensor coil. so probably tossing it is the correct remedy sigh.

    it does still work, just a question of how much value a dehu is that you have to turn off the hottest & muggiest weeks of the year.

    1. I can not imagine, how you could measure the rotational speed of a sealed hermetic compressor, although it is always 5-10% below line frequency. If the line frequency drops, it would run slower and draw less current. But you can check your mains voltage. If that drops, the current increases.

    2. Be sure the air flow though the unit is unrestricted. I had a dehumidifier with similar symptoms which I solved by taking the unit outside, removing the cover, and then forcefully washing the two sets of coils with a garden hose. After washing, I allowed the dehumidifier to sit outside disassembled in the sun for several days to be sure any water which may have gotten into the electrical parts was baked out. The dehumidifier has a filter screen which I clean every two weeks when the maintenance light comes on, but the coils still got dirty. Mostly it was the evaporator which was full of slimy algae-like gunk that seemed to be the problem area.

  6. Didn’t know you were allowed to work on AC type refrigerant gasses without licensees etc anywhere, not something I’d ever looked for mind… But I know to do it properly requires lots of gear and the knowledge of how that gear works, plus the gasses are not good to vent, so just dumping a refill can in it seems almost like it should be criminal…

    Still actually good to know such things are available if it is ever required, and I would be very surprised if a reasonably slow leaking device just regassed without a real fix is not a massive environmental saving over a whole new one… Still seems like the pressure testing, pump down, flush routine is the way it should be done though…

  7. First: You are lucky to be able to buy R134a so easily as a private person. In Europe it is very difficult due to over active eco-freaks. Luckily there is Aliexpress.
    Second: It is really not a good idea to leave this tap valve in the refrigerant circuit. They will leak. Normally they should only be used for removal of old refrigerant before working – if some is still there. Then the capped third line (fill line) on the compressor should be opened with a pipe cutter (no saw) and a proper schrader-valve should be brazed in to fill the unit.

  8. Do these refrigerator cans actually have refrigerant? I mean, Last year, I was looking to buy one (to fill my car) but none of them convinced me enough. They all seem “el cheapo” chinese cans, and I doubt that they will fill my circuit with refrigerant

  9. That “something” that “may” be in automotive refrigerant to reduce leaks is probably propane, which would cause rubber parts like O-rings to expand.

    The cut-out switch is there for a reason. Bypassing the switch is not smart. A seriously over-heated compressor could start a fire, especially considering the compressor in the unit shown in the video is in a plastic case. A refrigerant leak could also cause the system to lose lubrication oil which circulates along with the refrigerant. Loss of oil could aggravate over-heating. As a matter of fact, many dehumidifier models similar to the one pictured were recalled due to fire hazard. I believe serial numbers may be checked at the US CPSC web site to see if a given unit of a dehumidifier model is subject to recall. Many different brand dehumidifiers in the recall were all manufactured by one Korean company.

    Home dehumidifiers are closed systems. All the connections are brazed and there are not O-rings or joints which would become loose allowing the refrigerant to leak out. If the unit is low of refrigerant, it is because a corrosion hole somewhere allowed the gas to leak out. A responsibly done repair job should include fixing leaks. We don’t need any unnecessary R-134A gas added to the atmosphere.

    Last of all, there should not be ice on the evaporator. The point is to have condensate drip into the reservoir, not freeze on the evaporator. Ice can form if the refrigerant charge is too low or the air is dry and the unit is set for an unrealistically low humidity. There should be a thermistor in a clip attached to the left side of the evaporator. The thermistor is monitored by the control board and should disable the compressor from running if the evaporator reaches water freezing temperature. Icing might happen if the thermistor is not making good contact with the evaporator.

  10. Just what I was looking for. I figured it was the refrigerant as the fan & compressor were running but no water collection. Thanks for the video – very helpful !

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