Air Handler/blower motor is intermittent and acting weird


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Old 05-15-15, 10:45 PM
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Air Handler/blower motor is intermittent and acting weird

Hello!

I'm having trouble with the air handler/blower motor randomly cutting in and out, or not coming on at all when set to cool. It happens in both the auto and on positions. The manner in which it cuts off and on is herky jerky and intermittent. It might cut out for a half of a second then run for 30 seconds then off for 10 seconds then back on for 5 seconds etc etc. Sometimes it is more like quick hiccups or a staggering, if that makes sense. It usually does this for a minute or two and then stops working completely. Other times it wont come on at all, and sometimes it will stay on as it should even with a few hiccups at first. It starts cutting in and out immediately when turned on even when it's been off for days. It does seem to come on and blow as it should on a call for heat however. I only tried the heat once though, because it was a very humid day and already a muggy 81 degrees in the house, but it worked at a time when it wouldn't work at all on cool.

Other info:
The compressor and outside unit turns on each time as it should. I always change the filter regularly and it has a new one in it currently. The capacitor for the blower motor is almost a year old. The thermostat (basic big box digital Honeywell) is a year old with brand new batteries and it is properly wired (4 wires R/W/G/Y) with seemingly good connections at the stat and furnace terminals. I haven't jumped the wires at the thermostat as of yet. Mainly because I don't want to blow a fuse, transformer, etc., if that's possible, and then have double the troubleshooting work if I could've just ruled it out with a meter to begin with. The thermostat face uses pin connectors to connect with the sub-base/wiring, and the switches/controls are on the face only. So there's no way to check any readings with a meter at the thermostat itself while in a call for cool or on setting, etc. if that is even necessary.

So, could it be a bad thermostat, bad stat wiring, bad relay or board? Maybe a weak motor or other? The unit is a 23 year old Goodman that has little to no info for it on the internet. If anyone can pretty much tell what is wrong by my description, or could give me a rundown on how to troubleshoot my way to the culprit, I'd appreciate it greatly. I'm in the south and it could turn 90+ degrees at any moment now. I am comfortable with a meter and electricity, live or not, btw. If you need any other info I'll gladly give it. Thanks!
 
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Old 05-15-15, 11:27 PM
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Ultimately the blower motor is connected thru a relay. Your problem sounds like a defective relay.

Can you post the model number of the Goodman air handler ?
 
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Old 05-15-15, 11:35 PM
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The furnace model is Goodman HCA075ND3R. If the air handler section has it's own model number, then I'll have to get it sometime tomorrow. Thanks!

What's the best way to test to see if the relay is bad?
 
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Old 05-16-15, 12:05 AM
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That's the model number for a Goodman gas furnace ?

So far I haven't located the service manual.
 
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Old 05-16-15, 10:25 PM
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Yes. It's hard to find much info on it at all, and similar Goodman models from that period. The wiring schematic and some other things are labeled on the unit, but I just need some basic how to's on testing the relay or the other possible parts that could be the problem. Since the relay sends to the blower motor, I would assume I could just check for power to the relay, then power at the blower motor or the output terminals on the relay that go to it when running and see the voltage drops and/or no voltage when it doesn't come on? Correct?

If a picture of the schematic made it easier to diagnose on your side, I can snap a few for you.
 
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Old 05-17-15, 05:28 AM
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A schematic would help and any pics of the board also,you are on the right track testing work back from the motor to see where the conductors are attached to the board or relay.
Geo
 
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Old 05-17-15, 07:50 AM
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http://www.tennis-villas.com/show_fi...62&type_lib=22


Looks like you have an old Consolidated furnace. How long has it been since this this was professionally inspected?

I would turn off power and remove the fan center to inspect for burned wiring behind it to help this fan issue but the heat exchanger should be inspected.
 
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Old 05-18-15, 07:41 PM
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Ok. Here are the schematic pics and one general pic

Sorry it took so long. It's been busy around here

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Last edited by PJmax; 05-18-15 at 08:30 PM. Reason: Reinserted pics
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Old 05-18-15, 07:47 PM
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There is not enough definition to see schematic. Can you post the model number on that control ?
 
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Old 05-18-15, 07:56 PM
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I resized them in the blue links. It has the control number at the bottom. Are they still not defined enough?
 
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Old 05-18-15, 07:57 PM
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I would remove the two 1/4 inch hex head screws and inspect for melted wire connections behind that diagram. The door switch wires to the fan relay often melt.

Looks like the left screw has already been removed...
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Those old consolidated furnaces were wired very much like this...
 

Last edited by Houston204; 05-18-15 at 08:17 PM.
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Old 05-18-15, 08:16 PM
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Okay. I didn't notice any burned or melted sections, but I'll make sure to check those again. I tried to get a meter in there twice, but both times it decided to work properly the whole time lol. So I'll try again. On the relay, I was checking for power in at the upper left purple and lower left black and had 120V. Then I was checking power out at the top right yellow and bottom black hi speed and had 120V, but it was working properly at the time. Are those the correct terminals to test it according to the schematic?
 
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Old 05-18-15, 08:25 PM
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Purple and Yellow do not appear in this image. I see orange and black.

Post some pics of the controls under the diagram for better assistance.
 
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Old 05-18-15, 08:29 PM
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As far as it being a Consolidated, you tipped me off on that before the last winter actually . I did have it inspected because of that info you provided, and I was up there with him checking and asking lots of questions. The exchangers, etc were good and there wasn't any of the rust build up luckily. It was pretty clean for its age actually. I bought and installed plenty of new carbon monoxide detectors and new combination ion/photo smoke alarms just to be safe though.
 
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Old 05-18-15, 08:34 PM
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I recommend annual inspections every Fall with any Consolidated furnace.
 
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Old 05-18-15, 08:39 PM
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I was referring to the other schematic 1 pic where it shows the blower motor relay connections in the center of the photo. That is what it looks like in the elec box with the purple, yellow, etc. connected just like that portion of the schematic. Has terminals labeled 1-6. I'm probably wrong though. I'll try to take a photo tomorrow, but it's stuffed and that piece is behind all the wires, so I'm not sure how visible it will be. The transformer and what I'm guessing is the fan switch is in there as well.
 
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Old 05-18-15, 09:09 PM
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Yeah, I was trying to follow the fan wire/thermostat into the relay . So according to the smarter section you colored on, I need to check black hi speed and white neutral after the relay, maybe at the blower motor itself for power beyond the relay? Then the orange after the door switch and what else for power into the relay?

Edit: I hadn't put that left screw back in yet when I was taking the pictures
 
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Old 05-18-15, 09:28 PM
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Are you sure that you measured high voltage on purple?
It looks like purple is the 24 volt signal from the stat G terminal to energize high speed fan operation.

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I would expect relay terminal 1 to be power from the door switch and power to the transformer.
Terminal 2 is the normally closed terminal to the fan limit for medium speed fan.
Terminal 3 is for the high speed fan operation.

(But it could just as likely be 4,5 and 6 in use since you have a double pole - double throw relay)
 
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Old 05-18-15, 09:35 PM
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120V on purple and whatever was on the bottom left terminal. I can't say for sure if it was the black going to the fan switch, but it's pretty much laid out the same as the schematic there. 2 yellows and a black on the right
 
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Old 05-18-15, 09:46 PM
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It looks a lot like this one, but may be 5 poles instead of 6

OEM Amana/Goodman BT1256502 Fan Relay

I'll take a picture with the cover off. If I can't get a good enough picture of the relay itself, I'll try to trace the wires back and draw out what's going where

The only other thing I noticed is on the stat wires, both at the stat and the furnace, I had 26V on the red/yellow(cool) and red/white(heat), but only 22-23V on the red/green(fan). Not sure if that little of a +/- matters much?
 
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Old 05-18-15, 09:55 PM
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I would measure the 1 to neutral (white), 2 to neutral and then 3 to neutral.

I am not sure what measuring the low voltage purple wire to the high voltage terminals will tell me.

1 is high voltage common from the door switch and 2 is N.C. (normally closed) to the fan limit switch which starts the medium speed in heat mode.
3 is N.O. (normally open) to 1.

When 24 volts is applied to the purple wire it closed 1 to 3 and opens 1 to 2.

If I measure 24 volts between yellow and purple (the relay coil) and I do not get fan operation, I measure 3 to neutral for 120 volts AC.
( I actually jumper 1 to 3 with my 1000 VAC rated needle nose pliers but I don't think I am supposed to type that:NO NO NO
 
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Old 05-18-15, 09:58 PM
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Oh, you have a peanut relay instead of a DPDT relay.

I don't like those relays much.
You should still have a common, a normally open, and a normally closed terminal.

You should see 0 volts at those low voltage locations with a demand present.
24 volts between Y and C would indicate a cooling demand.
24 volts between G and C would indicate a fan demand.
24 volts between W and C would indicate a heating demand.

24 volts between G and R indicates Potential and no demand for fan
 

Last edited by Houston204; 05-19-15 at 05:33 AM.
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Old 05-20-15, 08:26 PM
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Well, it's been working the last 2 days so I'm just waiting on it to act up again. I have a question out of curiosity in the meantime. Do relays intermittently stick or get stuck? Because 2 days ago I killed the power to the unit at the breaker for a bit (the only time I've killed the power to it thus far) and it's worked fine ever since I flipped it back on (for now at least). Does that sound like more evidence/something typical of bad relay behavior, or more like anything else? Just curious. I like learning from all angles.
 
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Old 05-20-15, 08:54 PM
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Yes, relays can give you intermittent problems.

I would still recommend measuring for 24 volts to the relay coil and 120 volts between N.O. and Neutral and between N.C and Neutral when it acts up again.
 
 

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