Is Your A/C Unit About To Die? This Tool Doesn't Lie 

Just happened to my neighbor. Bad Cap caused unit Fan to stop working. Compressor goes into Thermal lock. He calls the AC repair man. The AC man tells him the Compressor is shot and that he needed a whole new systen at $22k.... I told him to wait for the motor to cool down and we replaced the Cap. All is working well now.

You want to pull ALL your wires off first, then test. There's a chance that the MEGGER could be checking windings all the way back in your system. Even if the wires are disconnected on the other end, you don't want to be checking the insulation against wires hanging out of the compressor. Also, it's best to sand back the copper pipe on the compressor and use that as your ground.

I just updated my central heat & ac unit It was a Fedder installed in 1972. Replaced system not because the compressor failed but the ac system developed micro leaks. 3 in the last 4 years in different areas. With the insane cost of R-22 to recharge a 5 ton system. I couldn't justify the cost. So replaced the whole unit with the help of your videos. The $ saved on utilities and installing it myself. It will have paid for itself in 3.5 years. Thank You for the help. I could not have done it without your videos. Keep up the great work.

I had THREE different ac companies tell me my 10-year-old compressor was shot and I needed a new system. Finally a friend of a friend came and looked at it and fixed it for less than $100 by simply replacing pressure switch. That was 10 years ago and it's still running fine today. Anyone else would have just believed them and paid for new system, especially after three different companies saying need new system. AC companies are worse than used car dealers!

As an industrial electrician of many year's make sure you disconnect and isolate the motor from all possible wire insulation and capacitor leaks to ground. Also the ground connection should be very clean to avoid a high resistance and give you a false reading. Nice video 👍

You are the "Man." You are demystifying the ownership of a home a/c system. Thank you for your efforts!

I had an AC guy about 12 years ago tell me my unit sounded tired and it was probably time for a new one. Still running great after 12 years.

As long as compressor is functional, all three windings are connected internally. Testing terminal by terminal as shown is also testing whatever is connected on the other two terminals and then some. All three wires need to be removed and just testing one terminal to ground will test all windings. That tester is low current, but puts out 500VDC. So if there is something at the end of one of the still connected wires that can be damaged by high voltage, you just damaged it. Or if a fan motor is connected at the contactor with the compressor, you are also testing that fan motor and wiring. Which, if you get a bad reading and mis-diagnose the compressor bad, when in fact it was the condenser fan or wiring, yeah..... Not to mention, there are other things that can indicate a failing compressor. Doing an insulation resistance test is just one test.

The manual for the insulation tester recommends that all leads be removed from the compressor at time of test. I would think that in some cases this could be important as other components still in the circuit could cause the lower 100 mega ohm reading you saw on the Goodman. The little tester does seem like a good idea. The manual says it applies 500 volts to the circuit at very low current and this is what is needed to properly do a test like this. Thanks for your video.

I know of one Lennox combo outdoor unit ( Air conditioner/ natural gas heat ) that is 35 years old and still working. My late father-in-law purchased the unit 35 years ago. He died in 2022 and a grandson purchased the house. The grandson had the unit serviced, ( coils cleaned, Freon checked, etc. ) that old Lennox unit is still working to this day. The newer units just do not last that long. I have purchased several AC, Heat pumps, over the years. I have three Lennox AC units that are 23 years old. I have purchased York, Trane, American Standard, and Heil units in the past for different houses. My latest purchase was a Heil Heat pump, three years ago. So far so good on it. Only got 13 years out of a 5 ton Trane Heat pump. Replaced the outdoor unit with an American Standard unit in 2017. So far so good on it. I don’t know which units are better than others, but a good HVAC guy makes a big difference. My experience has been that Lone Ranger type HVAC guys, or an HVAC guy who has one helper provide better results than HVAC technicians who work for large companies, who employ dozens of technicians. Those companies have to meet huge payrolls, whereas the one or two person HVAC company is under a lot less financial stress to meet payroll. A good HVAC person does not have to advertise to get all the business they can handle. I found a great HVAC guy back in 2003. He was just starting out on his own back then. I have since used him for all my new installs and all repairs. I told all my friends about him. He got so busy he had to hire a full-time helper. He has so much business, he can pick and choose his customers. He is honest, reliable, and always does excellent work. He never had to use paid advertising. Word of mouth is more powerful in growing a business than any type paid advertising.

I helped a friends mother. He told me at work that it was the original unit to her home. When I got there it was a Chrysler Airtemp . Built in 1964. Had a bad contactor. Replaced, cleaned outdoor coil , lubricated outdoor condense fan, ,, STILL RUNNING TODAY.

Bad motor windings (checked with this meter) are only one of many things that can fail in a compressor. This only tells you if the insulation in the motor is good or not.

I would completely isolate the compressor. And hook your ground to the component being tested. Testing like this it could be the compressor, the wires, the fan motor, the starting cap, or even the contactor.

Copeland states in bulletin AE4-1294 that megohm readings as low as 0.5 megohms to ground are acceptable. Besides the fact that this makes a scroll difficult to successfully meg (essentially impossible with a tool like the Supco M500 because it only reads down to 20 Mohms)

Wonder how many good reviews this guy actually have . We will never know how his customers really feel.

Fedders made the best A/C units on the planet. I still have a little 5K BTU window unit that's literally falling apart but still works.

They go on about recycling when all they should do is make things last. This is true for everything.

That’s why I am not changing out my 1987 Trane unit.

Love that silver RU-vid plaque in the background,your videos are a great help for people who are overwhelmed by the hvac technology and of course some not too honest contractors

I live in an rv park in Az. Many of these Park Models have been here since before 1982. Many of the rv's still have the original carrier pancake 2.5 ton straight cool ac with 7.5 kw heat strips and Coleman Saguaro park model, and you'd be surprised as to how many are still rocking. Performing very well I might add. Some have new fan motors but many are still factory, when I do a performance check the run caps are still spot on, and many haven't even been serviced in yrs, I do many a coil clean and install a tri-dem 3ply filter to keep their ducts clean for many yrs to come I will be getting a mega ohm to further prove to my customers that their unit is still good and performing as it should, not one of my service buddies has ever told me about a mega ohm meter before. Glad I came across your video in upping my knowledge

Metal nameplate, made to last. Printed sticker nameplate, 10 year product.

Thanks for all your help 🙏

I have a 10 12 sheer Coleman heat pump and it is going on 27 years old and still running fine!

While this tool can indicate a bad compressor, a good reading on it doesn't guarantee a good compressor. The motor may be hard to turn, causing excessive amperage draw even through the windings are good. Also, depending on the type of compressor, it may have bad valves in it; although, I suspect most are more of a rotary type that don't need valves. However, I'll agree that probably 99% of the time, if the windings are good, the compressor is good.

Thank you for your videos. I just replaced my condenser , A coil, line set and VTX. WE ARE COOL NOW.

You are checking the insulation level between the winding of the compressor and the ground using the ohmmeter. Higher resistance means better insulation to ground so less likely to short out. Insulation generally don't deteriorate unless the insulation material are not up to standard or compressor overheated numerous times causing the insulation to break down.

I wish I could buy an ac system back when things were built to last, I paid to have installed 2 systems since a bought my house, and same scenario on the current ac unit on my house is relatively new and started acting weird already, now I know why, things are not built to last anymore.

We all want you to install our new system. 🥰 I've used filterbuy your advertisement on this video. Got the exact filter I needed. Perfect. ( I was not paid to make this statement)

There are a few independent HVAC mechanics that will inspect your system and advise you honestly. My buddy just got a new furnace because his combustion fan was bearing was dry and seizing up. I replaced my sisters combustion fan for $350.00 in parts. Some businesses are directed to sell HVAC systems, they will say stuff like " I could fix this but something else could go next week"

Good info here! I've always been my family and neighbor mechanical and electrical handyman, cars, electronics, home appliances, you name it. I've done all my own HVAC work too. You just need a good attitude, patience, common sense and a mechanical aptitude. I always love to watch your videos for up to date info! Thanks!

Oh yeah, the unit is working fine and is about 21 years old, but due to this VID, I purchased the M500.....Tucson, Az. area (Sonoita actually).

Neighbor called me to come to her house. HVAC contractor was trying to charge her $320.00 to replace a wire on the condenser. I disputed the charge and fortunately the contractor tore up the work order. Two days later, she called me and said it had stopped blowing cold air. I walked over, looked at the condenser and the wire he replaced was burned up. Again! I told her wires don't just burn up. Something caused it. I looked at the contactor and saw it was completely burned. I went to a HVAC supply house not far away and bought a new contactor for $16 and new capacitor for $15, replaced them and the burned wire and it's still working three years later.

Fedder was a huge manufacturer of window/wall units in the 50s-60s.

I had to replace 3 fan motors over 20 years. Eventually when the unit died we realized the wrong jumper was used on the circuit board when it was originally installed and my fan had been running too fast according to the service rating for it's entire life! That explains why I kept going through fan motors. Luckily they were only about $30 each.

Thank you for this demo. Very valuable tool. Learn something from you every time. Also, the bottom line, they don't make them like they used too. That and the higher pressures sure do shorten the life of these things.

ohmmeter that uses higher voltage to check motor windings is a very good tool, but limited in scope of what it can tell you. many other issues with electromechanical devices that won't show up on resistance tests but kudos for giving average joe homeowners some direction in troubleshooting. I think a lot of consumers don't know the huge scientific and physics principles at work to remove the heat from the air inside of a structure and expel it outdoors (or vice versa in the case of heat pumps) and anything that can be done to demystify the process is always good.

I wish u live near me! U are such honest hvac tech

Many "THANK YOU!"s to you , sir! Dave, you *ROCK!* I'm so glad I follow your channel because so many people are rotten crud, liars, cheats, & thieves. Your honesty and character are a testament to you and your parents. May you be blessed for following our Creator's guidance. I've noticed that you try to help people protect themselves from evil ones. I commend you for your efforts & wish you the best. Have a GREAT day, Neighbor!

If you're going to meger the compressor you should remove all wires and then do your test on each terminal. Your test method could pickup carbon dust on contractors etc.

Thank you for the advice 🎉

My favorite first question when I call a HVAC company to fix one of my two heat pumps is “how old is the system”? When they do this I ask them for their 608-610 certificates and their Freon purchase license. They ask me why and I say if older system repairs are beyond your abilities I’ll need to call a more experienced HVAC company.

I have a home warranty through State Farm that covers my home HVAC system. The deductible is 500 bucks. It would be extremely interesting to me (and other home warranty holders) to see a video on how to troubleshoot and repair 500 to 700 buck problems. I’m not too concerned about work going over that amount because that’s when the warranty I’ve been paying for kicks in and I’ll let a pro sort it out at that point.

Just had a guy declare my AC not worth fixing today. It's a 33 years old Sears AC. He claims I'm very low on coolant. It uses R22, which he claims is $220 per pound. He stated he wouldn't sell me $1000 - $2000 of coolant for an AC that would just lose it in a few months anyway. The AC still works and feels cold, but freezes up constantly and can't pull the temp down (takes several hours to pull it down 2 degrees on a 75 degree day, if it doesn't freeze). No red flags with the guy. It's a local, reputable, company. $5K to replace it with an entry level Trane 2ton, soup to nuts.

we have two bryant heat pumps, and I keep a couple starting caps handy in my tool kit.

some good videos on how they rebuild a/c compressors and can see theres more that can fail besides the windings. most common is burnt capaciter and easy to replace. on an old mini split the remote receiver board and indoor pcb failed. i replaced them with a single universal pcb with onboard receiver. works great ali express about 25usd. worth using an under / over current protector as the expensive pcb's can die. also be very careful with caps as they can store electricity even if power turned off. i use insulated gloves and tools

Just ordered it on Amazon

Hi, nice video. Thanks!!! Saludos desde Tampa Florida

A meggar should be used on an isolated piece of equipment. If not, you are measuring the resistance to ground of whatever the other wires are connected to as well as the compressor. Also when using a meggar, it is actually measuring current flow, the lower the current the higher the resistance. The increasing readings are totally normal. They are normal because the circuit is acting like a capacitor, once the circuit is is charged , then can the resistance be determined. On the safety side the system will be "charged" after measurement. Be sure to short/discharge the tested circuit to ground before touching!

Thanks so much for this info. I will get one of these and test.

Love these videos, they fatten my wallet every time one comes out!

Could the Supco also be used with a smaller mini split system to check the compressor? Your channel is one of the best on YT. Very informative!

This tester looks for electrical "leaks" in the electrical conductors insulation inside the compressor. Nice! The compressor on my unit sounded like a rocks in metal can being shaken😅.

I sold Fedders A/Cs. Long ago in the NY metro area!

The tool tests electrical insulation and nothing else. It cares not what refrigerant is used, the condition of the refrigerant, or age. All it measures is the ability of wire insulation to keep electricity in the wires. It’s a marvelously useful tool, and can often warn you things are getting old. It really ought to climb all the way to the top of the green scale in quick order. If it doesn’t, electricity is leaking through the insulation - a sure sign things are about to go bad.

Actually, had different problem. it was a combination of the compressor and capacitor. It was showing 2 volts below spec. He suggested I buy an Install Hard Start Kit. This helps the compressor start up and come up to operating speed quicker. The start assist reduces winding stress and the production of winding heat, saving the compressor from additional strain and increases the life of the compressor. The heat pump is now 12 years old, so if I get another 2 years out of it of year-round usage in CT that is a pretty good life.

My blower fan on the air handler was not always coming on. The AC man says I needed a new system. I replaced my thermostat (15 years old) and all is well.

Fedders! the very first house that I lived in as a child had that brand. We are talking 1960!

I enjoy watching your videos, I appreciate you educating the masses. HOWEVER, I MUST take issue with what you said in this video. PLEASE correct me if I’m wrong. When you meg the compressor windings, that’s what you’re doing is checking the windings. Thats the “electrical” part of the compressor. It has NOTHING to do with the actual compression part. Hence your comment on “not drawing a proper vacuum” or “using old refrigerant” are COMPLETELY irrelevant.

My system is an 85, started looking at replacement options. It still runs reliably. I clean it twice a year. I wish things were still made as good as they used to be it a shame.

New stuff is made to fail, my grandmother had a GE refrigerator that was over 50 years old, it ran until the house got flooded and water got inside the compressor area and the people who help clean up threw it out.

don't know how many times a condensor needed replacement and get told 'you need a whole new unit'

Very helpful.😁

Good info.

My 30 year old Trane A/C unit quit working due to freon leaking. 3 different large A/C companies would not refill it they all wanted to sell me a new unit with the least expensive at $8k and highest at $17K. Finally a friend connected me with a real repair man who replaced the leaking valve, refilled the Freon all for just over $400. The one large A/C company that would refill my Freon wanted over $3,400. When this company asked me to share my experience with them on-line I posted what they wanted to charge me and what I actually paid with another repair man. The owner called furious and promptly told me I got ripped off and demanded that I take down the post he solicited from me. Last I saw my post was still there and 2 years later my A/C works fine.

Thank you

keep in mind of the old saying in the trade: compressors don't die, they're murdered

In our neighborhood bunch of us started to get written estimates and the diagnostic reports etc and posting those to our community facebook page. Naming and shaming these crooks was the best thing that could have happened to the residents and honest services companies. I had a company threaten a legal action about sharing the estimate and I happily asked them to go ahead, as I will request a civil jury trial and request discovery. That guy shut up so fast.

I know little about AC compressors, but the resistance of motor windings is only one test of a compressor health. Is this just step 1?

While I agree that often it is something like a capacitor for the reason a unit does not start. Electrical shorts, which can be tested with a standard multimeter, granted there will be a few cases where the short is not seeable at 9 vdc but those are very rare. But there are other factors beside this, a bad valve in the compressor would show a good compressor in this type of test. A better way of checking for electrical issues is both resistance of windings and current draw compared with exchange temps.

Try ur test by putting the ground clip on low side copper near compressor!

Awesome, thanks!

Fedders was the best Got a 5000 with old refrigerant and it cool a complete ranch house. No kidding Like an icebox and I still use it Thats why it still tested good Maybe oil filled cap I would like to dee the the difference of the electric draw though.

Thanks

Thanks!

Tha start capacitor went out on mine. To be fair, that central AC unit was built in 1967 so I cannot complain. Ended up replacing the entire system a few years ago as everything else was original and would no longer keep up on really hot days.

Compressors that test bad according to this megger are not necessarily bad. According to Emerson, you can have a good compressor megger out to as low at 0.5 megaohms, where this meter will tell you 20 megaohms is bad. Additionally, contamination can cause low readings and if you remove the contamination, you remove the low reading and the compressor is fine. I suggest reading Emerson Bulletin AE4-1294 for more details.

While I might use this to indicate if further testing is needed, I probably wouldn't condemn a compressor without checking further. Many "condemned" compressors tested at the factory show nothing wrong with them. "Studies performed by Copeland have found that compressors with megohmeter readings as low as 0.5 megohms still pass the hi-pot. There are many factors that affect megohm readings including contaminated refrigerant, oil level, refrigerant in oil and current leakage through electrical fusites or terminal plates. As mentioned earlier a single megohm reading cannot be used to condemn a compressor since many other factors are involved. However, limits can be placed on megohm values that dictate action be taken. Copeland has found that these limits are related to the rated voltage of the compressor. Megohm values equal to or greater than 1000 ohms per volt are probably acceptable. For example, a 460 volt compressor might show a megohm reading of 460,000 ohms or 0.46 megohm. Compressors with rated voltages of 208 to 230 volts would then be operable at megohm values of 0.208 to 0.230 megohms; for simplicity, Copeland has set the limit at 0.5 megohms before a compressor is condemned. Figure 1 shows the required procedure for checking compressors with a megohmeter. New compressors that have never been installed will not need any system clean-up procedures so long as the megohm reading is above 0.5. A baseline reading must be established for comparison purposes and since this is its first reading this will be its baseline"value. www.graycoolingman.com/uploads/1/0/6/6/10667336/copeland_4-1294.pdf

Per the compressor manufacturers, you can not test a scroll type compressor with a megger that has freon in it. Been there and it didn't work out very well.

Proves my beliefs. New stuff is garbage. I still run my r22 system.

I haven't thought of Fedders for years! 🤔

You could also just use a stand Volt-Ohm Meter that you probably already have... No need to buy a separate tool. Also, you should isolate components before testing them in this way.

The old one seems to be in better shape than the new one.

I’ve wondered if I install an Easy start Microair 368 on my 2 stage American Standard condenser would make a difference in prolonging the life of the compressor. Would installing it eliminate the need to replace the capacitor? I’ve read so much about the Micro Air on this channel. Thank you

There are many ways a compressor can be bad-bad valves-locked up -and that meter would test good-not the only way to test compressor and meter is just ONE

This may be a dumb question, can you use this on a refrigerator compressor? Thanks!

Luckily our ac guy is a friend of ours

My AC coil was replaced 2 years ago now, according to ac guy, it has a small leak! He said since it is aluminum, it is not worth repairing. Parts is still under warranty but labor/refrigerant cost me $900.00 two years ago. He said it is more now. I jokingly told the guy that I can patch the leak with bubble gum😂. Anyway, how can I be sure that the replacement doesn’t have a leak (damage from shipment), before they install it? Thanks!

To perform a DC Insulation test on any motor you need to disconnect all the external wires and then perform the test. Otherwise you are testing the motor and the external wiring through the windings of the motor. Also if the unit has any electronics you run a good chance of damaging them with the high voltage.

Will this meter work on variable speed compressors?

How much would an air conditioner at good price new or used cost for 1 acre of land or ~3000 square meters for a greenhouse? A unit that can lower temperatures to 2-3 Celsius or 41f?

If the compressor goes out, can the compressor itself be swaped out or would a new whole outside unit be purchased?

I used to use this when I first started in the industry, found it to be 50/50 when saying a compressor was bad. I would just tell the customer that one of the test showed the compressor was going bad so not to be surprised if it died suddenly. never sold a customer a new system or compressor based on that reading alone.

Great info. Dave. Hopefully we all last longer than our expiry date.....right Dave?

Dave, i'm getting ready to buy parts. How long would you let a line set run for. No burn out. 25 years or older. or could that copper still be good? What's the best practice. Less than 20 is good. Or 30+ years. Money is not the object. Quality and longevity. I feel like some techs would no question throw the old one out.

What exactly does that device measure? Is it measuring the quality of the insulation?

Can this device also be used to test capacitors

My original thoughts were that the compressor pump would be the component to go... Not the dielectric strength of windings. How does pump wear factor in... Or how do we test it? Just gauge pressure?

Could you do a video on heat pumps in cold areas? I’m from the same area as you and am wondering if it would be worth the investment. Any systems from hvac direct you would recommend?

Would this work on rv rooftop air conditioners?

How about the heater core that is wrapped around compressor? Testing it?