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Furnace Inducer Motor Troubleshooting! Top 8 Problems!
WEBVTT Kind: captions Language: en
00:00:02.050 --> 00:00:05.740 Hey guys this is AC Service Tech and today what we're going over is the top eight 00:00:05.740 --> 00:00:10.900 reasons why an inducer motor on a natural gas or propane gas furnace does 00:00:10.900 --> 00:00:12.680 not seem to be working. 00:00:12.760 --> 00:00:15.180 The inducer motors job is to actually push the 00:00:15.190 --> 00:00:21.040 exhaust gases out through the exhaust and it actually sucks in the intake 00:00:21.040 --> 00:00:26.040 right from here through the heat exchanger and through the burner tube assemblies. 00:00:26.280 --> 00:00:29.820 So the inducer motor is the first thing that ends up being turned on 00:00:29.820 --> 00:00:34.340 by either the relays or the control board for the heat sequence to turn on. 00:00:34.340 --> 00:00:39.360 So this needs to turn on first and then it's proven by a pressure switch. 00:00:39.360 --> 00:00:41.860 A pressure switch could look something like this 00:00:41.860 --> 00:00:47.140 or like this but basically they are sensing the negative pressure coming 00:00:47.140 --> 00:00:52.160 from either the inducer motor housing or through a condensate drain. 00:00:52.200 --> 00:00:56.700 In order to determine that this is actually working in that there's no clogs. 00:00:56.700 --> 00:01:01.239 Reason number one could be that the signal wire from the thermostat is not making it back to 00:01:01.239 --> 00:01:05.500 the control board in order for the control board to tell the inducer motor 00:01:05.500 --> 00:01:10.299 to turn on. So the way that we confirm if the control board is actually receiving 00:01:10.299 --> 00:01:15.789 this signal back from the thermostat is we have R coming to the thermostat and 00:01:15.789 --> 00:01:21.639 it connects to W and then W comes back as the 24 volt wire. So this is the hot 00:01:21.639 --> 00:01:26.170 wire and we can check it between white and common. So we have our multimeter set 00:01:26.170 --> 00:01:33.689 to volts AC and right now we'll go ahead and check and we see that we are reading 00:01:33.689 --> 00:01:39.639 nothing. So we got point zero three three volts and we are set on heat and the 00:01:39.639 --> 00:01:46.869 thermostat is calling. It says we want it set to 81 and it's 54 in the room so it 00:01:46.869 --> 00:01:50.679 definitely should be calling at this point. You can see that we actually have 00:01:50.679 --> 00:01:57.429 24 volts from R to C right here and what should be happening is the R and W 00:01:57.429 --> 00:02:01.419 should be touching and we should be getting 27 volts here and we're not. 00:02:01.419 --> 00:02:04.899 In this case you'd either have a problem with your thermostat itself or the 00:02:04.899 --> 00:02:08.649 thermostat wires and the way to determine if it's the thermostat face is 00:02:08.649 --> 00:02:14.050 what you could do is take the face off and then jumper from W to R and see if 00:02:14.050 --> 00:02:19.600 you have the same problem. So if we jumpered from W to R then that should 00:02:19.600 --> 00:02:22.870 tell heat to turn on. And the first thing that happens in the sequence of 00:02:22.870 --> 00:02:27.730 operation for the furnace is that the control board is going to send power to 00:02:27.730 --> 00:02:31.390 the inducer motor. So now we can go ahead and check our voltage. We can check from 00:02:31.390 --> 00:02:38.800 W to C. And you see that now we have 27 volts. That tells you that the thermostat 00:02:38.800 --> 00:02:43.480 face is the problem. If we actually took the face off and we jumpered inside the 00:02:43.480 --> 00:02:48.010 thermostat face from R to W then you know that this was the problem. So if you 00:02:48.010 --> 00:02:51.760 don't have mag jumpers what you could do is turn the power off and then you could 00:02:51.760 --> 00:02:57.280 jump the R and the W together with a wire nut. And then you can go ahead and 00:02:57.280 --> 00:03:02.019 check inside your furnace at your control board for W to C and you see 00:03:02.019 --> 00:03:06.160 that we have 27 volts right now. So this is problem number two. Once you verified 00:03:06.160 --> 00:03:10.480 that you have 24 volts from W to C and actually it's anywhere from 24 to 29 00:03:10.480 --> 00:03:14.530 volts, so once you've verified that you have a signaled calling for heat you 00:03:14.530 --> 00:03:17.980 want to go ahead and check for your inducer motor wiring. You want to make 00:03:17.980 --> 00:03:21.850 sure that you are finding the right wires here and you're following it from 00:03:21.850 --> 00:03:25.269 the inducer motor back to the control board. In this case I've already 00:03:25.269 --> 00:03:28.660 disconnected the wire and I have the probes in and I'm checking for voltage. 00:03:28.660 --> 00:03:34.570 So you see that the control board is not sending the 120 volts that it needs to 00:03:34.570 --> 00:03:39.620 the inducer motor. So in this case this would actually be a board problem. 00:03:39.680 --> 00:03:43.180 Any time you think it's a board problem you want to make sure that you're not quick 00:03:43.180 --> 00:03:47.109 to condemn the board. It's actually one of these relays right in here 00:03:47.109 --> 00:03:52.390 that would end up closing allowing the 120 volts to go through but you know 00:03:52.390 --> 00:03:57.310 there could be another issue such as a sensor or something like that but in 00:03:57.310 --> 00:04:01.450 that case you'll notice that the blower motor does not want to turn off so just 00:04:01.450 --> 00:04:03.850 make sure your limit sensors are working properly 00:04:03.850 --> 00:04:08.600 and that you don't have a lower limit gas switch and a propane furnace. 00:04:08.600 --> 00:04:12.640 Things like that before you end up condemning the board. In reference to checking ECM 00:04:12.660 --> 00:04:17.260 variable speed inducer motors, what we need to do is actually access the 00:04:17.260 --> 00:04:21.039 troubleshooting guide for that model number furnace and typically on the side 00:04:21.040 --> 00:04:24.640 right here there's gonna be a connector that you're gonna have to check 00:04:24.700 --> 00:04:28.140 DC voltage readings off of. Alright so you're gonna follow with the 00:04:28.150 --> 00:04:30.910 troubleshooting guide it says from that manufacturer and 00:04:30.910 --> 00:04:34.293 you're going to see the DC voltage values changing. 00:04:34.293 --> 00:04:35.620 Problem number three. 00:04:35.620 --> 00:04:41.290 What could happen is if you have a 120 volt or 240 volt inducer motor and 00:04:41.290 --> 00:04:45.040 your capacitor could be bad. So this is actually a capacitor this little 00:04:45.040 --> 00:04:48.880 block right here. So make sure that you have the power off, you're going to go 00:04:48.880 --> 00:04:52.390 ahead and disconnect the electrical connections off of there. You're going to 00:04:52.390 --> 00:04:58.410 go ahead and short out the terminals just like this. And this one says 3uf and 00:04:58.410 --> 00:05:02.590 250 volts. So we're gonna go ahead and test this with a multimeter. We're gonna 00:05:02.590 --> 00:05:09.120 turn this on to micro farads. So we're gonna have to hit this select button and 00:05:09.120 --> 00:05:14.470 then we're gonna go ahead and check our micro farad reading. We're gonna hold 00:05:14.470 --> 00:05:19.990 this in and you want to give it possibly up to even you know 15 seconds or so 00:05:19.990 --> 00:05:24.790 just in order to make sure that this is correct. So you see our reading right 00:05:24.790 --> 00:05:32.020 here is 2.3 uF. So this capacitor is actually more than 5% off. So you can 00:05:32.020 --> 00:05:35.080 replace this with a like stock capacitor that looks like this 00:05:35.080 --> 00:05:39.370 a capacitor that's bigger that looks like this. The difference between these two is 00:05:39.370 --> 00:05:44.080 the voltage right here. This is 250 volts and this one's 370 volts and it has to 00:05:44.080 --> 00:05:49.900 do with how much insulation is inside the capacitor. You have to replace this 00:05:49.900 --> 00:05:55.540 3 UF or 3 MFD with the same size so this one won't work because this is a 5 MFD 00:05:55.540 --> 00:06:00.100 capacitor but if you did have one that would say a 3 MFD that looked like this 00:06:00.100 --> 00:06:05.560 you could replace this capacitor with it. This capacitor has to be installed on 00:06:05.560 --> 00:06:11.440 typically its brown wires or one brown wire and one white wire and it has to be 00:06:11.440 --> 00:06:16.680 in place for the motor to even be able to start up and also to run. 00:06:16.680 --> 00:06:22.720 So number four, the actual inducer motor bearings could be seized. So in this case we can 00:06:22.720 --> 00:06:28.050 actually get into this shaft right here in order to try to spin it 00:06:31.520 --> 00:06:36.810 and we see that that one's moving freely. But you can get into one and you can 00:06:36.810 --> 00:06:41.160 kind of feel it it's really really stuck and once you get it spinning then it 00:06:41.160 --> 00:06:45.210 seems to be working. A lot of times it's upon an initial startup of the furnace 00:06:45.210 --> 00:06:50.040 for the first time in heating season. A lot other times it might just be in the 00:06:50.040 --> 00:06:54.240 middle of the heating season. You can tell this one is very easy in order to 00:06:54.240 --> 00:06:59.190 make sure that the inducer motor is spinning freely. On one such as this once 00:06:59.190 --> 00:07:02.550 again just make sure the power is off and you can't get into here so you just 00:07:02.550 --> 00:07:07.100 take your your thermostat screwdriver and see if you can get it to spin that way. 00:07:07.100 --> 00:07:11.900 If you notice that a motor has actual ports on it for oil those are not 00:07:11.940 --> 00:07:15.280 sealed bearings and those are the ones that end up needing to be oiled. 00:07:15.280 --> 00:07:18.840 If it ran out of oil and the bearings are seized then the damage has already 00:07:18.840 --> 00:07:23.320 occurred and that would be one that you would end up recommending replacing. 00:07:23.320 --> 00:07:26.880 But how you add the oil in is you just go ahead and take this tube right here and 00:07:26.880 --> 00:07:32.130 you put it right into the hole and then you go ahead and squeeze here your zoom 00:07:32.130 --> 00:07:35.940 spout until you have this basically overflowing. You don't want to overflow 00:07:35.940 --> 00:07:40.500 crazy amount but you do want to get enough oil in to make sure that you have 00:07:40.500 --> 00:07:48.710 that whole reservoir filled up. So we should be pretty darn close right there. 00:07:48.710 --> 00:07:53.100 Now just you know just because you see these ports right here does not mean 00:07:53.100 --> 00:07:57.060 that this is a non sealed bearing that needs to be oiled. 00:07:57.060 --> 00:08:02.280 You can actually look inside and there is no trough for the oil and it actually says sealed 00:08:02.280 --> 00:08:09.180 ball bearings. So these outer casings of the inducer motor are are made for a 00:08:09.180 --> 00:08:13.410 multitude of different model number blower motors. So this one this one 00:08:13.410 --> 00:08:17.250 happens to be one that has a sealed ball bearing and make sure that you do not 00:08:17.250 --> 00:08:20.960 put any oil down inside that hole for sure. 00:08:20.960 --> 00:08:22.890 This is problem number five and 00:08:22.890 --> 00:08:26.910 this inducer motor was out of a package unit and you can see that this one has 00:08:26.910 --> 00:08:31.530 some play in it. It actually moves back and forth like this and the problem with 00:08:31.530 --> 00:08:36.570 that was that the inducer wheel was binding on the edge by the heat 00:08:36.570 --> 00:08:40.440 exchanger and that was a problem. And then the inducer motor was not turning 00:08:40.440 --> 00:08:43.520 on it was actually just getting stuck. Alright so that's 00:08:43.520 --> 00:08:46.790 that's something that could happen or debris can be stuck in here maybe from a 00:08:46.790 --> 00:08:50.102 bird's nest and that's not allowing the motor to turn on. 00:08:50.102 --> 00:08:52.200 This is problem number six. 00:08:52.200 --> 00:08:57.140 In this case once again the inducer motors out of a package unit and the 00:08:57.140 --> 00:09:02.000 problem with this one was that the inducer wheel actually has fallen off 00:09:02.000 --> 00:09:06.980 completely due to rot. Alright so it's rusting and just rotting the metal right 00:09:06.980 --> 00:09:10.220 there and it's coming completely off. You can have something like this that's 00:09:10.220 --> 00:09:14.300 metal but you can even have plastic ones where these actually all fall apart 00:09:14.300 --> 00:09:17.990 on the inside and then jam the wheel and then basically you need to replace this 00:09:17.990 --> 00:09:19.480 or replace the entire housing. 00:09:19.480 --> 00:09:21.440 So problem number seven could be that the inducer 00:09:21.440 --> 00:09:25.820 motor actually is running but you're having some problem with proving that 00:09:25.820 --> 00:09:29.870 this is running with the pressure switch. So the sequence of operation for heat 00:09:29.870 --> 00:09:34.340 goes with the inducer motor turning on first, the pressure switch proving that 00:09:34.340 --> 00:09:37.820 the inducer motor is working in that and that there's no clogs, and then after 00:09:37.820 --> 00:09:41.840 that the ignition source gets turned on. And what could be happening is this 00:09:41.840 --> 00:09:45.800 pressure switch could not be proving that this is operating and I like to 00:09:45.800 --> 00:09:50.120 typically measure the pressure switch out with the SD man 6. 00:09:50.120 --> 00:09:54.860 Alright so this tool right here is very very useful because you can 00:09:54.860 --> 00:09:59.300 actually isolate the pressure switch completely away from the system just to 00:09:59.300 --> 00:10:04.490 make sure that this is correct or not correct. As well if you were going to go 00:10:04.490 --> 00:10:07.490 ahead and blow out these lines make sure that you disconnect them from the 00:10:07.490 --> 00:10:11.690 pressure switch before you put any pressure on them. Alright so then you can 00:10:11.690 --> 00:10:17.180 blow these out you could have a problem if the pressure switch tests good. 00:10:17.180 --> 00:10:21.260 You could have a problem with maybe your condensate trap for your 90% efficient 00:10:21.260 --> 00:10:26.480 furnace maybe that's clogged or maybe the drain piping is clogged or maybe the 00:10:26.480 --> 00:10:31.370 tubing like this tubing right here is clogged or maybe you have a clog in your 00:10:31.370 --> 00:10:36.500 exhaust or clogging your intake. Possibly maybe the heat exchanger is clogged and 00:10:36.500 --> 00:10:40.010 if that's the case, that's a very serious situation you want to make sure that you 00:10:40.010 --> 00:10:42.720 go ahead and verify if that is clogged. 00:10:42.720 --> 00:10:44.210 And then problem number eight could be 00:10:44.210 --> 00:10:48.590 that the actual inducer motor may be burned out. So you could do a quick sniff 00:10:48.590 --> 00:10:53.060 test in order to smell if the windings are burnt out and then in reference to 00:10:53.060 --> 00:10:56.030 testing it with resistance with your multimeter, you make sure that your 00:10:56.030 --> 00:10:59.660 furnace is off, you unplug the motor, and unplug the 00:10:59.660 --> 00:11:03.800 capacitor, and your first check will be on ground. So you see I have my one probe 00:11:03.800 --> 00:11:07.760 and ground. You never put your test probes in this part because you don't want to 00:11:07.760 --> 00:11:12.110 oblong the connections you always put them in the back part. So you can check 00:11:12.110 --> 00:11:17.030 right here and we're checking for a resistance values between ground and 00:11:17.030 --> 00:11:19.130 common, you see that we have none right there, 00:11:19.130 --> 00:11:25.130 "OL" over limit. We see that we have right here on ground to hot there's no 00:11:25.130 --> 00:11:30.320 problem, and just so you know when you have the two wires going to the 00:11:30.320 --> 00:11:34.580 capacitor the one that's brown and white, that one's actually touching 00:11:34.580 --> 00:11:41.030 the white wire inside of this 120 volt inducer motor right here. So we already 00:11:41.030 --> 00:11:45.200 tested the white so we know that that is no problem. You see that we once again 00:11:45.200 --> 00:11:50.540 have OL and we'll check this one anyway. 00:11:50.540 --> 00:11:51.980 And you see that we have OL. 00:11:51.980 --> 00:11:57.170 So we know that the windings did not short against the ground frame and we can 00:11:57.170 --> 00:12:01.430 see that our ground is intact another way to do this is actually to try to 00:12:01.430 --> 00:12:05.240 take, you know this is all painted, but you want to take a your ground 00:12:05.240 --> 00:12:10.820 connection right here at your motor. The next test that we'll do is we'll just 00:12:10.820 --> 00:12:17.140 check the windings and we'll go from common to hot. 00:12:21.740 --> 00:12:22.700 And you see that we have 00:12:22.700 --> 00:12:28.640 34 ohms or resistance. We'll get the same reading if we go from hot to this 00:12:28.640 --> 00:12:33.350 capacitor wire with the white on it. Should have about 34 ohms of resistance. 00:12:33.350 --> 00:12:39.920 The other one said 34.7 this one says 34.6 ohms and now we'll 00:12:39.920 --> 00:12:46.160 go ahead and check from hot to the other capacitor wire. And you see that we're 00:12:46.160 --> 00:12:53.300 reading 117 ohms. And now I'll go ahead and check from common to hot. 00:12:53.300 --> 00:12:57.020 Basically what we're making sure of is that we don't have 0.0 ohms 00:12:57.020 --> 00:13:02.000 or resistance and that we don't have OL because OL would mean that the 00:13:02.000 --> 00:13:05.750 windings are burnt apart and 0.0 ohms would mean that the windings 00:13:05.750 --> 00:13:10.480 are all melted together. And you see that we have 152.3 ohms. 00:13:10.480 --> 00:13:11.940 So this motor checks out good in 00:13:11.950 --> 00:13:15.040 reference to the resistance readings. If this inducement motor was bad we would 00:13:15.040 --> 00:13:19.540 probably smell the burnt windings and we'd probably also have a OL 00:13:19.540 --> 00:13:23.769 reading across the windings. 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