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Furnace_AC How to Troubleshoot The Control Board
WEBVTT Kind: captions Language: en
00:00:08.090 hey guys J here with word of advice TV 00:00:10.94000:00:10.950 in the comment sections for some of my 00:00:13.12900:00:13.139 a/c fixing videos people have been 00:00:14.74900:00:14.759 asking me to make a video about how to 00:00:17.39000:00:17.400 troubleshoot a control board and they're 00:00:19.49000:00:19.500 actually really not that hard to 00:00:20.75000:00:20.760 troubleshoot unfortunately to 00:00:23.09000:00:23.100 troubleshoot a control board you do need 00:00:24.74000:00:24.750 a meter so if you don't have one you 00:00:26.77900:00:26.789 might need to get one so take your 00:00:28.49000:00:28.500 furnace doors off or your air handler 00:00:31.54000:00:31.550 and most air handlers or apprentices 00:00:35.75000:00:35.760 will have a control board some of the 00:00:37.31000:00:37.320 older ones will not for the most part 00:00:40.49000:00:40.500 there is a control board in every 00:00:42.20000:00:42.210 furnace typically it'll be located right 00:00:46.49000:00:46.500 in front of the blower housing where 00:00:48.29000:00:48.300 your blower motor is once in a while 00:00:50.18000:00:50.190 it'll be in the upper section too so the 00:00:52.45900:00:52.469 way it works is you got power coming in 00:00:54.86000:00:54.870 to the furnace or the air handler right 00:00:57.04900:00:57.059 here it goes into your power switch so 00:00:59.45000:00:59.460 if I turn that off it turns everything 00:01:01.01000:01:01.020 off then you see or the furnace so power 00:01:03.65000:01:03.660 goes into there the switch is on 00:01:05.71900:01:05.729 so then power goes into here line 00:01:07.94000:01:07.950 voltage and then from the junction box 00:01:10.42900:01:10.439 it goes down and the first place to stop 00:01:13.21900:01:13.229 set is the door switch as you can see 00:01:15.77000:01:15.780 mine is taped in order to check voltages 00:01:17.87000:01:17.880 you do have to have your door switch 00:01:19.58000:01:19.590 taped most furnaces will have a door 00:01:21.80000:01:21.810 switch either on the left or right or in 00:01:23.71900:01:23.729 my case in the middle so tape that or 00:01:25.99900:01:26.009 put a screw in it so it stays shut and 00:01:27.71000:01:27.720 then always keep in mind that it is live 00:01:30.28900:01:30.299 you have 120 volts somewhere there so be 00:01:33.64900:01:33.659 mindful and don't touch any terminals so 00:01:35.60000:01:35.610 you don't get shocked so after the power 00:01:37.78900:01:37.799 goes into the door switch if the door 00:01:39.83000:01:39.840 switch is closed the powered end goes 00:01:41.84000:01:41.850 into the control board typically it'll 00:01:44.89900:01:44.909 be marked line blind voltage goes into 00:01:48.49900:01:48.509 that terminal so from the door switch it 00:01:50.27000:01:50.280 goes into there and that's what powers 00:01:51.98000:01:51.990 up your control board so after power 00:01:54.53000:01:54.540 goes into it the circuit board part of 00:01:56.84000:01:56.850 it brings power to whatever is calling 00:01:58.63900:01:58.649 for power like the blower motor or the 00:02:00.49900:02:00.509 inducer igniter so what will happen is 00:02:02.99000:02:03.000 sometimes let's say during the AC season 00:02:05.99000:02:06.000 the AC outside will turn on everything 00:02:08.93000:02:08.940 seems to be working good but the blower 00:02:10.63900:02:10.649 motor inside of the furnace is not 00:02:11.93000:02:11.940 turning on sometimes what's wrong is 00:02:14.05900:02:14.069 that 00:02:14.30000:02:14.310 the board is not sending power to the 00:02:15.94900:02:15.959 blower motor and simply not powering it 00:02:17.90000:02:17.910 up or other times you have voltage 00:02:19.97000:02:19.980 coming in from the transformer 24 volts 00:02:22.79000:02:22.800 into the control board 00:02:24.05000:02:24.060 but then that voltage does not come back 00:02:26.08900:02:26.099 out that means there's some kind of a 00:02:28.19000:02:28.200 circuit or a diode or some of resistor 00:02:31.13000:02:31.140 inside the board that got burnt out so 00:02:33.08000:02:33.090 in a nutshell how I was taught is if 00:02:35.93000:02:35.940 there's power going in but no power 00:02:38.05900:02:38.069 coming out that means the board is bad 00:02:40.16000:02:40.170 so what I like to do when I start is I 00:02:42.44000:02:42.450 set my meter to voltage my door switch 00:02:45.14000:02:45.150 is taped shut so I have power going 00:02:47.15000:02:47.160 through I like to first verify that my 00:02:49.46000:02:49.470 furnace is getting power and a lot of 00:02:51.97900:02:51.989 times a good indicator will be the 00:02:54.55900:02:54.569 indicator light the diagnostic indicator 00:02:56.69000:02:56.700 light if that's blinking then most 00:02:59.00000:02:59.010 likely you do have power you have 120 00:03:00.86000:03:00.870 volts and you have 24 volts but not all 00:03:03.50000:03:03.510 furnaces will have that light so what I 00:03:05.42000:03:05.430 like to do is check it quick so if you 00:03:08.18000:03:08.190 pull off the wire that goes to your line 00:03:10.67000:03:10.680 terminal from the door switch to our 00:03:13.40000:03:13.410 line terminal just pull that off stick 00:03:18.71000:03:18.720 one meter lead in there and with your 00:03:21.77000:03:21.780 other terminal you need to find a common 00:03:24.05000:03:24.060 somewhere I like to just use a the 00:03:27.31900:03:27.329 comment on the transformer just because 00:03:29.18000:03:29.190 it's more accessible than the rest of 00:03:30.86000:03:30.870 them and if you just stick your lead 00:03:32.90000:03:32.910 into the middle speed of that 00:03:35.03000:03:35.040 transformer common there you should get 00:03:38.53900:03:38.549 a hundred twenty volts so if you look at 00:03:40.25000:03:40.260 my meter 00:03:42.37000:03:42.380 you see 120 volts so from my line 00:03:47.08000:03:47.090 terminal to a common you're supposed to 00:03:49.97000:03:49.980 have 120 volts and I do have voltage 00:03:51.86000:03:51.870 there and that means my furnace is 00:03:53.96000:03:53.970 getting power and it's getting past that 00:03:55.67000:03:55.680 door switch so I can plug that back in 00:03:58.96000:03:58.970 next what I like to check is that my 00:04:02.12000:04:02.130 transformer is getting 120 volts as well 00:04:05.53900:04:05.549 so I'd like to loosen the connectors on 00:04:07.97000:04:07.980 the transformer black and white that's 00:04:10.64000:04:10.650 going to be your 120 volt side usually 00:04:12.89000:04:12.900 it's a black and white wire I like to 00:04:15.50000:04:15.510 just leave them like half on plug like 00:04:17.84000:04:17.850 that so I could put my meter leads on 00:04:23.68900:04:23.699 so you put one lead on the Colin from 00:04:26.21900:04:26.229 the transformer and one lead on the 00:04:29.68900:04:29.699 primary hot side and if you look at my 00:04:32.73000:04:32.740 meter you got 120 volts so the board is 00:04:37.29000:04:37.300 sending power to the transformer now if 00:04:42.03000:04:42.040 your board is getting powered if you 00:04:45.33000:04:45.340 check your line voltage on your line 00:04:47.18900:04:47.199 terminal and it's getting 120 volts but 00:04:49.89000:04:49.900 it's not sending power to your 00:04:51.27000:04:51.280 transformer so if you check the white 00:04:53.34000:04:53.350 and black on the transformer and there's 00:04:54.71900:04:54.729 no 120 volts then your board is bad and 00:04:57.75000:04:57.760 it's not sending power to that 00:04:59.01000:04:59.020 transformer next thing you want to check 00:05:01.29000:05:01.300 is the secondary side of your 00:05:02.70000:05:02.710 transformer so it transforms at 120 00:05:05.10000:05:05.110 volts into 24 volts so if you go on this 00:05:08.52000:05:08.530 side usually I mean there are always 00:05:10.98000:05:10.990 different colors the secondary side 00:05:12.62900:05:12.639 lines the secondary side wires but they 00:05:16.77000:05:16.780 will be opposite of the 120 volts side 00:05:19.11000:05:19.120 if you put both of your leads on those 00:05:21.74000:05:21.750 you should have somewhere around 24 00:05:24.83900:05:24.849 volts and there you go I have 28 volts 00:05:28.62000:05:28.630 so my transformer is sending 28 volts 00:05:31.83000:05:31.840 out and also there's a fuse in line with 00:05:35.33900:05:35.349 that sometimes it'll be on the board I 00:05:37.52900:05:37.539 don't have a place for it on the board 00:05:39.48000:05:39.490 so mine is placed in on the hot side 00:05:41.76000:05:41.770 coming from the transformer the 24 volt 00:05:43.89000:05:43.900 side and then what I'd like to do is 00:05:45.90000:05:45.910 track where those 24 Volt wires from the 00:05:48.24000:05:48.250 transformer go in my case it goes into 00:05:51.21000:05:51.220 the one side goes into the fuse my fuse 00:05:53.21900:05:53.229 is good goes out the other end and goes 00:05:55.52900:05:55.539 into the small X plug then the other 00:05:57.68900:05:57.699 wire right here the common also goes 00:06:01.17000:06:01.180 into the small X plug so the 24 volt 00:06:03.99000:06:04.000 wires go straight into the control ward 00:06:05.85000:06:05.860 sometimes they'll have their own 00:06:07.02000:06:07.030 terminals it'll be called secondary one 00:06:09.21000:06:09.220 and secondary two so if I put my meter 00:06:11.49000:06:11.500 leads into the molex plug a hot side and 00:06:15.57000:06:15.580 the common 00:06:19.12000:06:19.130 as you can see I have 28 volts going 00:06:22.45000:06:22.460 into the control board and after the 28 00:06:26.59000:06:26.600 volts goes into the control board it 00:06:28.54000:06:28.550 will come out on the thermostat terminal 00:06:31.03000:06:31.040 strip which is right down here in mine 00:06:33.13000:06:33.140 it will look different on every furnace 00:06:35.68000:06:35.690 but for the most part it'll be in a row 00:06:37.57000:06:37.580 like this where it says WY RG c it for 00:06:42.25000:06:42.260 common so the next thing you want to 00:06:43.60000:06:43.610 check is R which is power to common or b 00:06:48.43000:06:48.440 or c sometimes do so if I check voltage 00:06:53.08000:06:53.090 between R and common as you can see on 00:06:56.08000:06:56.09000:06:56.53000:06:56.540 I do have 28 volts so the board received 00:06:59.92000:06:59.930 28 volts and it's putting out 28 volts 00:07:03.28000:07:03.290 at that terminal strip now if you're 00:07:05.74000:07:05.750 getting voltage that far then chances 00:07:07.99000:07:08.000 are your control board is good usually 00:07:09.94000:07:09.950 you're gonna lose voltage somewhere 00:07:11.77000:07:11.780 before that also what you can find 00:07:13.57000:07:13.580 helpful is on the back of your furnace 00:07:15.55000:07:15.560 door most of the time there will be a 00:07:16.99000:07:17.000 wiring schematic and it could be hard to 00:07:19.96000:07:19.970 follow like mine for example has a bunch 00:07:22.27000:07:22.280 of lines and stuff but if you look at 00:07:25.06000:07:25.070 just look on the schematic until you 00:07:27.49000:07:27.500 find the power supply which in my case 00:07:29.44000:07:29.450 is right here look for the black and 00:07:31.42000:07:31.430 white and then you can kind of follow 00:07:32.92000:07:32.930 those lines where they go into the board 00:07:34.66000:07:34.670 and I'll explain sometimes what color 00:07:37.24000:07:37.250 those wires are what terminals they go 00:07:39.55000:07:39.560 into and you know sometimes it will help 00:07:42.16000:07:42.170 you track down on the wires that way 00:07:43.83000:07:43.840 also if you do end up needing a new 00:07:46.21000:07:46.220 control board the way you go about 00:07:48.40000:07:48.410 looking for the new replacement board 00:07:50.29000:07:50.300 most of the time on the board itself 00:07:52.60000:07:52.610 it'll tell you it's model number or part 00:07:54.40000:07:54.410 number and in my case it even tells me 00:07:56.56000:07:56.570 replace with CNT to 184 so if I ever 00:08:00.43000:08:00.440 needed a new board all I had to do is 00:08:01.93000:08:01.940 look up this board right here and get it 00:08:03.64000:08:03.650 on Amazon or whatever and that is the 00:08:06.01000:08:06.020 basics of troubleshooting your control 00:08:07.72000:08:07.730 board sometimes it'll be some goofy 00:08:09.73000:08:09.740 situation and then it's not as easy to 00:08:11.56000:08:11.570 troubleshoot and you do kind of have to 00:08:13.24000:08:13.250 go case by case basis but for the most 00:08:15.82000:08:15.830 part if you follow that procedure you 00:08:17.62000:08:17.630 will be able to figure out if your board 00:08:19.63000:08:19.640 bet is bad or not so once again as a 00:08:22.12000:08:22.130 reminder if you have power going into it 00:08:24.04000:08:24.050 but it's not sending power out the board 00:08:26.71000:08:26.720 is bad same for a furnace for example if 00:08:29.77000:08:29.780 you have power going into it but it's 00:08:31.39000:08:31.400 not sending power to 00:08:33.04000:08:33.050 let's say your inducer motor or your 00:08:35.38000:08:35.390 igniter then your board is bad I hope 00:08:38.44000:08:38.450 that makes sense to you if you didn't 00:08:39.91000:08:39.920 quite get it you can ask me in the 00:08:41.05000:08:41.060 comments below and I'll try to explain 00:08:42.31000:08:42.320 it better down there and that is all I 00:08:44.35000:08:44.360 had for you today thank you so much for 00:08:45.85000:08:45.860 watching don't forget to match that like 00:08:47.29000:08:47.300 button on your way out and we'll see you 00:08:48.76000:08:48.770 next time 00:08:50.20000:08:50.210 [Music] 00:09:07.06000:09:07.070 you
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