This one covers the repair of the ECM motor end bell when the surge control thermister fails. The thermistor will sometimes overheat, causing an open circuit that results in the motor not running at all.
Did this with my gas furnace blower motor - after being threatened with a $1,000 motor replacement. Now I have a RHEEM aircon compressor fan motor which looks to be a similar type to the interesting range you show. So, inspired by your excellent video, I shall give it a try! Thanks!
Thanks a ton! I had found another video first that was specific to my unit (Trane), and had already ordered the replacement thermistor. I thought we were going to sweat it out (100 degree heat wave!) for the next few days until I could receive and solder it in. Then I saw your video with the simple explanation to jumper it temporarily ... and here we are, sitting in a nice air-conditioned house instead! Thanks so much.
Thanks so much!!! Because of this I was able to get my air going again in Louisiana. This is the second time this has happened. I kept my first motor and tried this trick, reinstalled it, and it’s blowing perfect. Thanks!!!
Hey Grayfurnaceman. I recently watched this video and it is EXCELLENT. I am a mechanical engineer by profession. I am very well-versed in mechanical engineering, software development, and hardware design. I am also very hands-on in my career/passion with assembly and soldering. I have 2 zones in my home, each with their own condenser and air handler. I had these replaced about 3.5 years ago with American Standard systems in both zones. My air handler in one of the zones recently stopped working. The coils were frozen up...I had this issue in my last home and found that my contactor on the condenser was stuck, so I replaced it and this solved the problem. In my "new" home, before I ran a bunch of diagnostics, I purchased/replaced the contactor for about $15 without doing too many diagnostics (I live in Florida and we have lot's of insects down here that get into everything). The new contactor works fine as I see the condenser fan turns on when I reduce the temp on the thermostat (same specs as the original contactor). When I realized that the blower motor in the air handler was not turning on, I called the company that installed my A/C systems, and they want $600-$800 to remove and replace the blower motor (motor is free under warranty, but the labor is NOT free under warranty). When I questioned the company about the number of hours it would take to do the job, I was told that it would take only about 1.5 hours for the labor. So in an effort NOT to get ripped off, I did some searching and found your RU-vid video regarding the thermistor replacement. Thank you. This was an EXCELLENT video. I purchased a new thermistor with the exact same specs from DigiKey. Last night, prior to the thermistor replacement, I checked the resistance with my digital multimeter from coil to coil and found about 9ohms between terminals 1-2, 1-3, and 2-3. I then checked from terminal 1 to GND, 2 to GND, and 3 to GND and all were OL. Perfect. I was totally convinced that the thermistor was the root cause of for the blower motor not turning on. So I clipped out the old thermistor and soldered the new thermistor to the terminals that were sticking up out of the epoxy potting compound. When I reassembled everything and turned the power back on, I was so upset to see that the blower did NOT turn on. Breakers are ON in both the panel and on the air handler. I did find an A/C parts distributor in Pompano Beach, FL that has a replacement blower motor for $265 (that includes the blower and ECM module) that I could replace myself. I would rather purchase the new blower motor for $265 and install myself rather than get the free warranty replacement motor and then pay $800 for labor. The person that I spoke with said that the chip would essentially program itself once installed. The company that wants to charge me $800 says that the chip needs to be programmed by a technician. Can you make any sense of this? Self-programming or special programming required by a technician based upon brand, model, etc.? Can I purchase just the ECM module or a fully programmed motor assembly with the correct ECM module. The OEM blower motor in my air handler is ZHONGSHAN BROAD-OCEAN MOTOR CO. LTD. ZWK702B006067 (ZKSD-250-10-4), ELECTRONICALLY PROTECTED A0, CONT AIR OVER, 208-230V 50/60Hz, 2.6A 1/3HP 1050RPM. Do you have any other suggestions? TIA. --Neal
This worked on mine. Almost 100 degrees today with snow and freezing temps in the forecast in two days. Got the central air running right now and will switch the stat to heat in a couple of days. Thanks for the knowledge on an inexpensive repair over a very expensive replacement.
@@grayfurnaceman this worked for me too. I have a replacement module coming tomorrow but this temporary fix will get me through the day of grueling heat. Thanks so much for sharing! Subscribing.
My Trane XV80 blower just went out, so I pulled the ECM and looked - SG379 thermistor, burnt at the leads, and cracked! Ordered one on the ‘zon for $9, desoldered the old one and jumpered it while I wait. Contact pad on bottom is delaminating, but still in one piece. Slap it all back together, and whooooommmmm goes the fan! Thanks Gray!
I just bought and installed an $800 ECM blower motor, then saw this video. I checked the thermistor in the old motor and guess what. It fell apart in my fingers. Thanks for the video. I'll fix the control board and have a spare motor.
I'm an HVAC tech and just replaced a customers ECM module for a good $1000. I still had his old one in my van and took it in to my lab to take a look at it. It is the one with the black epoxy, but to me this epoxy is identical to black silicone. It's obviously a type of silicone that doesn't have the properties that typically corrode certain metals. But I did meticulously pick out chunks of silicone around the thermistor to expose the leads. I tested them for continuity and the thermistor was still good. I then cleared as much of the silicone around the entire outside edge as humanly possible and removed the two tamper resistant screws to try and remove the electronics board and see if I could get at some other internal parts. I was successful with aggressively removing the entire electronic assembly by prying up under the side connector and working the whole thing up with large screwdrivers (the silicone was even oozed out underneath it and holding it pretty good along the bottom). The ground wire goes straight through and it mounted underneath, I had to cut that wire to get the board out. Once out, you have access to nothing, the whole rest of it is still covered in the annoying silicone and the underside is a flat plastic piece with no access to behind the circuit board. If the thermistor is not fried on this particular module, it's pretty much a done deal. There is way too much work involved in trying to remove the silicone to get at other parts, and to do so without causing more damage. Unfortunately, a lot of these 3.0's are like this to make sure people can't fix them without busting the bank.
In my opinion, there is no effective repair for these silicone filled end bells. Except for the thermistor which must have the opportunity to cool. GFM
I wonder why they do that with the silicone Bs. Considering they don’t last long enough for anything to corrode! Could it be so that people can’t easily make this repair, but instead have to buy the ridiculously priced replacement?
Wow I always knew that there had to be something that could just be either jumped or replaced and you are a genius, of course I'll try it out first 😊 but I'm pretty sure you nailed it
ANYONE having an issue with their furnace fan needs to give this a try before investing anytime or dollars. I had our local "pro's" come have a look and quote over $2.5k to replace both the motor and module. Then tell me that they are on back order and might as well replace both the furnace and AC for $14k. Happy that there are honest folks teaching us who want to learn. Thank you genuinely for the lesson and the savings. With much appreciation, Brian and Co.
I'm assuming they mistook your non-blinking blank stare (which was most likely due to shock) of the initial quote as an "okay" and then to really put the screws to you and go for the whole enchilada.
For the end bell… a heat gun persuades the epoxy to expose the board. Last ditch effort anyway. Thanks for the video on the thermistor, very insightful.
Good info here. Just a bit of confusion from some, including me, where you misspoke at 1:26. Thermistors are not used in surge protectors or power strips. Only MOVs are used in those items. It is important to understand that MOVs are used in parallel with line voltage whereas Thermistors are in series with the line voltage. To check if the Thermistor has failed, scrape clean the connecting wires and see if there is some resistance. The markings on the thermistor in this video indicate it is a 22mm 1 ohm 20a NTC (negative temperature coefficient, resistance decreases with temperature) device. I have notice the newer x-13 motors have markings indicating the same 1 ohm and conform to UL1434.
I believe the device you're looking at is a metal oxide varistor (MOV). It's purpose is to absorb voltage spikes and is the primary component of a surge protector. Many electronic devices have these installed to protect circuitry. If the voltage spikes High Enough they will open rendering the device useless.
It is not an MOV. Both MOVs and Thermistors have many similarities. One of the differences in this application is the powering up of the capacitors. A thermistor will limit the inrush of current while the capacitors are charging. GFM
I pulled a genteq motor out of my mother's a/c the other day. Its a 101564 with an aluminum heatsink and 2 capacitors similar to the one in your video. I'm having a hard time identifying the thermistor though. It says 1914 and Ntc 1,0. Before I pulled motor Lenox thermostat said indoor unit reports problem. This is the 4th time in 11 years and out of warranty now. Thermistor doesn't look burnt though. Any idea what thermistor I would use as a replacement? Thanks.
Thanks for video. SG381. That is the thermistor in my old air handling unit ECM blower motor control module. But nobody, including Digi key, has that thermistor for sale. I'm wondering what is an equivalent thermistor I could use, equivalent to SG381.
If the thermistor is bad, would the motor move at all? I have an ECM142R that just jerks 3 times, spins slowly not even 1 turn, pauses about 15 seconds and repeats. The fan moves easily when given a push, but it won’t continue spinning. Thanks
The ECM fan module just failed on my American Standard TAM9 air handler. The unit is 2 years and 4 months old. It has a 10 year parts and 2 year labor warranty. Nice it fails just after the labor part of the warranty ran out. My installer said they would cover the labor cost and not charge me. They ordered a new one from the American Standard supplier in Las Vegas a week ago and it still hasn't come in yet. Now they had to reorder it. When it does come in they will have to drive to 90 miles to Las Vegas, pick it up and drive it back. I guess I should be happy it failed when the temp is in the low 90's instead of 110-120 F in the summer. Had a Carrier unit for 25 years and the only problem I had was 2 different control boards blew out within 2 months of each other. The new electronic stuff is just more BS to break and cost more to fix.
What a great video. Thanks so much for sharing your knowledge. I do have an special request; I watched your 2 videos in reference to ecm failure on the air handle motor/ecm. I work for an apartment complex and I like to fix not to replace parts like many techs do. We been replaced over 70 units still under warranty. The brand is Broad Ocean and 1/3hp you probably by now fixed a few of them. Can you share the thermistor number that this particular ecm uses? I can’t find the number for it online. I’ll like to give it a try, I know that this brand it’s full of epoxy resin that manufacture días to avoid the fix. Thanks in advance.
Hey, I have the same end bell like the one with the black epoxy that in the video. My fan start for a second then turns off. I have tested the supply and control voltage goes to the bell they are withing spec. Is there any way I can test the thermistor?
Do you have any experience with the " Fan Handler" ECM motor controller kit to replace an existing PSC motor and convert it to an ECM motor? I was considering doing this to my furnace. Thanks.
This type of controller has been around for a long time. The idea of continuous low volume fan operation is a good one. However, this is not a conversion to an ECM motor. ECM motors use far less energy than PSC motors in the low speeds. In most cases, the low volume position of this device will use about the same energy as high speeds. As for operating the fan continuously, you can do the same thing by placing the fan in the on position. On most furnaces made in the last 30 years, the fan on position puts the fan on low speed. GFM
If the thermister reads 1.3 - 1.5 ohms at room temperature, does that mean it is bad? It is rated at 1 Ohm. Also, What causes the mosfets to go bad? Can they be replaced?
Great video....thanks. Can a bad thermistor potentially cause an X13 motor to not turn off once the call for AC is done? Or, cause the blower fan to just turn on by itself and run till it maybe turns off? This started with my 5 year old Rheem 5 ton unit about a month ago. I've replace these parts in tube amplifiers and also used them to limit the inrush of current to the tubes to prevent premature damage. Just curious as it would be cheap to fix before replacing the motor.
they went to "potting" them in epoxy/other due to thinking it was vibration causing solder joint fatigue failures, which likely caused the burnt trace issue you've seen. it very well may have been a factor.
Funny you say that, I just replaced an ECM motor on my Goodman furnace with a new spare I happen to have (long story). Anyway, the controller board with microprocessor is mounted to the blower motor housing with no type of vibration isolator, talk about vibration fatigue of tiny soldered connections. Add to that, (15) connections need to be unplugged (mostly to the controller board) to slide the blower housing out. The controller board is mounted to a metal panel that’s mounted to the blower housing using (5) screws, I removed the panel with controller board attached and gently set aside before I attempted to jockey the blower housing out. Clearly saving every penny to manufacture, the controller board could have been remotely located to someplace less vulnerable using an extended wiring harness.
If an ECM fan motor runs only occasional including very delayed starts (10 - 30 minutes), starts than stops multiple times during a single cycle, occasionally starts up fine only to shut down several minutes later, all of which occur during either a call for cooling or fan-only... is it the case that a thermistor is either good or it's bad? Can it cause the sporadic ECM blower motor issues I'm experiencing or is it always a complete failure of the motor? The compressor starts up and runs fine.
thanks for this video! I have a question: My thermistor is bad but the trace where it solders, the pcb is burnt. I've cleaned out the burnt area and most of the copper is still good. What should be used to fill the hole under the trace? Epoxy resin?
Can I just use a driver (something like 25A-A2P5N104 ALLEN-BRADLEY) to run this motor without the bell? Single speed on an off setup? Or any other cheaper driver
My Trane variable speed fan suddenly quit yesterday. The HVAC tech said it appeared to be the ecm yet they only replace the motor ecm combo for $1500. I pulled the ecm out and it has the SL22 thermistor. I checked the existing one and it has continuity. So is that part good and I have another issue on the board?
First, I would jumper out the thermistor. If it runs, the thermistor is the problem. If not, I would look for a repairman that actually troubleshoots the system. The motor seldom fails. It is easily checked out for continuity. GFM
If you didn't electrically disconnect at least one leg of the thermistor then you could be getting a false continuity reading from backfeeding in the circuit. I agree with GFM on jumping.
Its correct name is a VARISTOR a thermistor changes its resistance with temperature. A VARISTOR normally is open circuit but when high voltage transients come in they become a very low resistance to clamp the incomming spike. Hopefully they have saved the control circuitry.
Yes you are correct interesting device so it is in series with the circuit to limit current. I assume these devices are going open circuit, Must first investigate these devices as a means to limit surge current to DC powered SOLAR inverters. The inrush current to charge up capacitors on first turn on can be quite excessive,
Has anyone had one of these controllers power on and will struggle to spin up. 120v or 240. either way it just cycles on and off. is this an issue with this thermistor as well? it seem to start fine but just doesnt have enough oomph to get to full speed.
If the thermistor is shot then the motor will not run at all? My furnace's blower motor speed has been fluctuating, sometimes slowing down enough to cause the temperature limit switch to trip; it will be running fine and then you can hear it dip then speed back up, after a couple of these sequences the furnace gets hot enough to trip. Since it is running does that mean it wouldn't be a simple fix like the thermistor? I believe I have a Genteq 2.3 motor in my York Affinity modulating furnace.
The thermistor is a negative temp coefficient resistor that starts out with moderate resistance when cool then lowers in resistance when it warms up with motor current draw. The primary purpose of it is when power is first applied the AC to DC rectifier-filter capacitors gets a high current surge to charge up the filter capacitors. The thermistor, when cool, limits this power-on initial surge current. Shorting out the thermistor can result in the AC breaker popping open. It also puts more stress on motor controller rectifiers and filter capacitors. Most X13 ECM motor controllers remain powered with DC filter capacitors always charged up with high DC voltage as long as air handler AC power is present. Turning the motor on and off, as well as speed control, is done by the 24vac speed connections, or digital control inputs. This is why sometimes when motor controller is bad the motor just continues to run all the time.
This part is a current limiting thermistor, placed in the system to limit current draw in case of a surge in amperage. It is not there for charging capacitors. GFM
Great video. Question is how to diagnose the thermister failed. Measure the resistance? OL resistance is failed, or others? Find the problem is half success to resolve the problem.
The easiest way is to cut the leads off then wrap them together. If it works, replace the thermistor. You can run it with the thermistor bypassed. It protects the electronics from surges. GFM
in theory it does "auto-resets" with each and every thermal cycle... the problem often is large power surge/drop outs cause severe high current surges and blows them apart. say nearby or direct lighting strikes to power lines, possibly transfer to and from backup generator to utility power and downed lines from stroms causing high voltage spikes on lower power lines. say a 14.4HV or higher distribution line comes down and hit's a 7.2KV line, bam double the voltage at lower power buildings. whole house surge protection is wise and surge protectors at the HVAC units as well ( still no 100% guarantee, as they work by SHORTING the excess flow to ground/tripping breaker/fuses)
I think you've got it backward on the thermistor... the thermistors in these circuits are NTC (negative temperature coefficient devices). So as they heat up the resistance decreases. The design is such that the device passes it minimum current on startup (power up) and then heats up and passes more current as the filter capacitors charge. The reasoning of the design is to limit power up, inrush current due to the initial charging of the two large rectifier filter capacitors. Thermistor part number SL22 IR020.
It is not backward. It has nothing to do with capacitor charging. In fact, the 2 capacitors are 1000 microfarad which will never overload anything. They are there to eliminate spikes in the line. GFM
How do you get the board out for the ones that have the black insulation everywhere? I have one of those and I'm trying to cut around edges but it's not coming loose.
What about when the blower just won’t turn off even after the thermostat is satisfied and the temperature is met. I have to manually hit the breaker to shut the air handler off. Is that part the problem for these ECM motors
What Varistor do I need to order for my York unit I looked at ordering one online there was over 3,000 to choose from! Only letters I could make out on my burnt Varistor was NTC Can anyone help Or know what type of voltage I need
@@grayfurnacemanso I’ve removed my old burnt thermistor and just soldered the wires together. At this point am I just not protected from the motor overheating? Do you know anywhere you can buy a used ecm?
This has 20A capacity, why couldn't you use a 20A fuse in this circuit instead? There are many filters before this point and I'm looking at the fan motor and see no reasons for this to have failed. Much like in the auto Fusible Links that just failed from cycling more than any true issue with anything. I ran into this on my garage MAXIMUS LED light, after one month it failed, found a guy that just put a fuse in place of the thermistor so I tried it as well. It's been working great for 8 months or so.
I changed the thermistor in my motor but now the fan keeps running (at a lower speed) after the burners have turned off... I replaced the limit switch but that didn't fix it... any ideas?
We never know for sure why they fail, but my thoughts are surges in the power line may damage them. You can also install a surge protector in the power line to the furnace. GFM
Well you were close on why it's used... Thermistor is used to prevent inrush current. To slow the current to the capacitor in this case, as to not pop a breaker. It in no way is there to protect anything like a fuse. Just my 2 cents. You can jump it out but risk blower a breaker on start up. Think about it, what is there to protect on these modules? Nothing. Anyways have a good day.
There has been a lot of back and forth on this issue. Not saying anyone is wrong, but I have seen many power strips with surge protectors that use this same device. GFM
Cause replacing them pays the shi*ts. Charge the customer change it out and move on. One thing that I’ve learned in my 17 years of hvac experience is NICE GUYS FINISH BROKE. Sad but true.
You will make about the same amount of money minutes the few hundred dollars unit cost. So you can charge the same service fee and labor but save your customers a few hundred dollars.
@@grayfurnaceman Unfortunately for me mine failed. It wouldn’t even turn by hand at all. The new problem just started. Now 5 years later the motor won’t shut off unless I turn it off at the circuit breaker. My board is fine and the thermostat. It won’t even respond to it for me to shut it off with the thermostat . The blower fan will just start up by itself. I did hear it ramp up and down in speed. What could cause the module to do this?
mine went after someone hit a power line in the neighborhood. Motor just stopped. I have an EON HD03. I metered for resistance across the thermistor and I do have continuity, getting about 1.1 ohms with it still in the circuit, does that mean it is good and something else on this went ? caps look fine, can't get to the rest.
@@grayfurnaceman I can't get to the rest of the board, buried in epoxy, I guess my only choice is to buy a replacement. If the in rush thermistor is bad what would it meter in ohms ? i.e how can you tell if yours is bad ? visual inspection looks OK.
