Furnace Blower Fan Cycles On/Off During the off Cycle

[petehall347]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

did you try everything including from 6.30 minutes ?

[Longbow]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Based on what you've said so far, your thermostat and the control board (new) are OK. The problem must be inside the motor itself. More disassembly if you are having fun. Is this blower motor a BSL - Electronic motor? If so, that is likely where your problem is.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

"did you try everything including from 6.30 minutes ?" Thank you, Yes, I did.

Hello.... I think I found the problem................

Last-night when I opened the yellow wire ( at one of the two wires cable) the fan motor no erratic run problem, still testing.

PS: the yellow wire is for cool system, why two of them.

Chassis GND to condenser... which condenser? in this system has four condensers, two outdoor condenser, one in the ceiling and one at top of the furnace?

PS: Maybe I mixed up condenser with evaporator

[Longbow]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

The schematic inside the furnace panel is all you need. Difficulty here is due to incorrect assumptions. Furnace motors have multiple speeds. Fan Only mode is typically a slow speed. Heat or Cool operates at high speed. One of your lower speed windings (could be up to 5 speeds in some units) is intermittent. The fan motor itself is the problem. Go to the fan motor connections on your schematic...all the speed connections will be there along with the start capacitor, which should also be replaced regardless.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

"Furnace motors have multiple speeds"

In the diagram shows IDB indoor blower has three speed LOW, MED and HIGH

the start capacitor I've changed to a band-new one.

PS: The Furnace work OK only problem is the blower motor run erratically?

[Longbow]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

In the diagram shows IDB indoor blower has three speed LOW, MED and HIGH

Yes. I'm trying to suggest that your intermittent motor operation occurs when the motor is in slow speed. As soon as AC or Heat is selected, the motor works fine, because it is switched into high speed. This information suggests that there is an intermittent short in the low or medium speed windings. It adds up to a motor problem, which is not a DIY repair. Get a new motor.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Thank you very much, How can I test an intermittent short in the low or medium speed windings?
Can I test blower with meter and hit with wood stick?

Reference:
Step by Step Procedure for Troubleshooting a Blower Motor from a Furnace and AC System!
https://www.youtube.com/watch?v=flbUtLMeSOQ

Troubleshoot the gas furnace fan
https://www.youtube.com/watch?v=ChD1GTEPHR4

How to replace a Blower Motor - furnace AC HVAC repair
https://www.youtube.com/watch?v=iqFE3qDNS2k

[keeney123]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Thank you very much, How can I test an intermittent short in the low or medium speed windings?
Can I test blower with meter and hit with wood stick?

Reference:
Step by Step Procedure for Troubleshooting a Blower Motor from a Furnace and AC System!
https://www.youtube.com/watch?v=flbUtLMeSOQ

Troubleshoot the gas furnace fan
https://www.youtube.com/watch?v=ChD1GTEPHR4

How to replace a Blower Motor - furnace AC HVAC repair
https://www.youtube.com/watch?v=iqFE3qDNS2k

You can observe the AC current and AC voltage on the motor. So when the motor is running fine take down the voltage and current readings of the motor. When the motor slows record the readings again. Compare the resistance calculations. One other step is to verify at the breaker that is supplying power to the furnace fan stays at the same voltage on both good and bad readings. You will see a resistance decrease with a partially shorted windings.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Thank you keeney123: "current readings of the motor"

I almost forgot I had a clamp on current meter, will find it and test with it....

[srhofmann]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Here's some clarification on your situation.

1. Your blower runs at high speed in A/C mode black wire to motor
2. Your blower runs at low speed in heat mode red wire to motor

1+2 - look at the schematic

A short in the blower motor will not cause it to turn on and off during the off cycle. During the off cycle NO power should be going to the motor, since it's turning on something on the control board is causing power to be sent to the motor.

You need to put a voltmeter on the control board when the blower is running when it should be off and see if it being powered from the A/C high speed or heater low speed wire.

Could you take a look at the blink codes again ,also when it runs the blower does it also run the inducer/power vent motor?





Let us know what you find and we'll take it from there.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

srhofmann: Thank you very much.

They said : that happened mostly on daytime, and all night is quiet. Why?
In this cool and hot system, the cooler's condenser(i dont know the name?) is at top of the furnace, has water marks all over the furnace, I need to open to check the water leak from the cooler condenser, and the air filter has been very dirty( like fur coats) is that gonna has impacted to the system?

[Longbow]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Goodman model NO. GMP075-4 Blower Fan Motor turn on and off irregularly while the thermostatic FAN switch is at off position,

I read all this several more times and I see that all this intermittent fan operation happens when the FAN SWITCH is in the off position, not on. In other words, the thermostat is not sending the furnace a call for heat or for AC, but the fan starts up intermittently. Most thermostats have a FAN ONLY switch. Is this the switch you are talking about?

No call for heat, No call for AC, FAN ONLY switch is OFF - Is this summary correct?

Then, if so when the fan turns on by itself, what speed does it run?? If you are lucky you can hear it, but you can also measure to see which speed winding is activated. If FAN ONLY switch is ON, what happens?

Blower motors continue to run after the gas turns off and until the temperature sensor in the heat exchanger drops below a certain temperature. Pulling the wire off that sensor will tell you if it is faulty (intermittent). In other words, the furnace might think the heat exchanger is still hot.

[petehall347]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

I read all this several more times and I see that all this intermittent fan operation happens when the FAN SWITCH is in the off position, not on. In other words, the thermostat is not sending the furnace a call for heat or for AC, but the fan starts up intermittently. Most thermostats have a FAN ONLY switch. Is this the switch you are talking about?

No call for heat, No call for AC, FAN ONLY switch is OFF - Is this summary correct?

Then, if so when the fan turns on by itself, what speed does it run?? If you are lucky you can hear it, but you can also measure to see which speed winding is activated. If FAN ONLY switch is ON, what happens?

Blower motors continue to run after the gas turns off and until the temperature sensor in the heat exchanger drops below a certain temperature. Pulling the wire off that sensor will tell you if it is faulty (intermittent). In other words, the furnace might think the heat exchanger is still hot.

this is what i was trying to explain earlier ...
you have done a much better explanation than i did ..

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

I appreciate for your time, Thank you for" I read all this several more times."

"Is this the switch you are talking about?" .........Yes.
"when the fan turns on by itself, what speed does it run?"...... no cure but pretty fast
"If FAN ONLY switch is ON, what happens?" the fan bowler turns on.

PS: If I set up a temperature from thermostat,and put on heat, the furnace works flawlessly.

[srhofmann]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Everyone reading this thread needs some clarification.

1. You said you changed the main board. Does the board still have blink codes or is it on without blinking?

It should not be blinking if the board and all the sensors are working correctly. The best way to check this is to turn off the power to the furnace and then disconnect ALL of the thermostat wires at the furnace. Turn the power back on. Light shouldn't be blinking. If it is stop here and troubleshoot the blink codes. If it isn't blinking, you can then call for heat by jumpering R to W on the control board. If the furnace calls for heat and then starts the blower without any blink codes we've verified the furnace doesn't have any major problems. Hook the thermostat back up.

Let us know what happened.

Until this is done all people can do is guess at what the problem is.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Good news, the Furnace PCB comes in now, so I will do it tonight, I'm kinda nervous.

I did some home work:

HVAC Goodman fan control board replacement
https://www.youtube.com/watch?v=lktkwnQQ4mo

PS: look at 0:09 He use the bar clamp to turn on the AC power, that is a good tips.

Easily Remove a Furnace Control Board.wmv
https://www.youtube.com/watch?v=FFx3-3ChT58

Goodman GMP075-3 Control Board Replacement
https://www.youtube.com/watch?v=0Qiyt6rNMcI

Replacing Goodman Furnace Control Module
https://www.youtube.com/watch?v=fbvyGJyJsGY

Repairing HVAC Furnace Control Board Relay - How to fix air condition faulty circuit
https://www.youtube.com/watch?v=0J9_ypacZMA

[petehall347]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

i thought you already tried a new board ?

[vinceroger69]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

i did too when i was reading this thread.

[capwizard]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

Sorry, about the wrong descriptions. I hope change the PCB will correct the Furnace Blower Fan's problem.....

PS: im gonna change the PCB means I am going to change it but not yet...

PS: Aren't you guys invented the English?.........

[Longbow]

Re: Furnace Blower Fan Cycles On/Off During the off Cycle

"Is this the switch you are talking about?" .........Yes.
"when the fan turns on by itself, what speed does it run?"...... no sure but pretty fast

Well, find out which speed it is running before doing any other troubleshooting. The point we are missing here is the METHOD. Don't skip around from guess to guess. You are no further along than when you started - so don't become an HVAC technician!

"If FAN ONLY switch is ON, what happens?" the fan blower turns on.

I guess you mean that the fan turns on and stays on. If so, what speed does the fan run at when you flip the FAN ONLY switch on? Important!