Goodman GMP060 furnace fan always on


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Old 09-19-13, 10:14 AM
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Goodman GMP060 furnace fan always on

We bought a house recently and I noticed that the fan is always on.

Our setup:

Mechanical thermometer
Goodman GMP-060 furnace
Furnace control board 1012-933D

What I've diagnosed/noted:

- The thermostat works fine to control heating/cooling with the one exception that regardless of the fan switch position, the fan is always on (the switch has "on" and "auto" positions)

- Disconnecting the fan (green) wire at the furnace control board does not turn the fan off

- The control board's LED is in fast blinking mode, which according to the schematic on the door indicates switched primary wiring on the transformer. I switched the wiring on the primary, and the LED is still in fast blink mode.

- With the door off, when I push in the door safety switch, I can hear a relay click and the fan come on.

- When I unplug the "heat" speed wire from the control board (that goes to the fan), the fan no longer runs. So it appears that the control board is always activating the "heat" speed of the fan.

I think all of this means I need a new board, but I wanted to see what you all thought!

Any/all inputs appreciated.

Thanks,

Carl
 
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Old 09-19-13, 10:57 AM
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If I remember correctly the other action to take for the rapid flashing error code is to switch the secondary wires from the transformer. Those are the two wires coming from the 24V output side of the transformer probably red and blue wires. If you can locate those two wires coming from the transformer post which terminals on the control board they are connected to. Also the two primary wires you switched please post which terminals they are going to. The black wire normally comes from the blower door switch and should be on the L2 terminal on the board and the white wire should be on one of the terminals with the "block" of white wires marked N.
 

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Old 09-19-13, 11:11 AM
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You have a great memory! The instructions exactly say what you remembered, the secondary wires can also be switched.

The secondary wires off the transformer go to a modular plug 9 position plug that plugs onto the board. From the schematic, it looks like the blue and red wires are going to the right pins. I didn't switch the wires, but now I realize that I can do this on the transformer side. So I'll try that.

The primary wires go:

- Black (on terminal marked "120V" on the transformer) goes to a terminal on the control board marked "Primary Trans" that is right next to the L2 terminal on the main board. From the back of the board, it looks like these two pins are tied together.

- White (on terminal marked "COM" on the transformer) goes to the 2nd terminal marked "primary trans" - right next to the block of N white wires. Also from the back of the board, I can see that it is tied to the block of N white wires.
 
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Old 09-19-13, 11:22 AM
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It is kind of hard to picture what you have but:

Is the wire on L2 coming from the wire that goes to the blower door switch? That is where the 120V to the control board comes from

On the terminal next to L2 should be the wire that goes into the 120V transformer side.

L2 and the terminal next to it are tied together. L2 from the door switch powers that terminal to power the transformer.

That white wire on the transformer marked "COM" is in the right place.

Before you switch the red and blue wires let's make sure we have the black wires on the correct terminals.
 
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Old 09-19-13, 11:28 AM
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You've got it right, my description below must have not been clear. The black wire on the transformer is on the terminal next to L2 which is the 120V to the board.
 
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Old 09-19-13, 11:34 AM
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Ok. It sounds like those wires are on the correct terminals. You said you switched the wires in your initial post. When you started, was the white wire on the terminal next to L2?

Have you verified voltage going into the board, into the transformer and out of the transformer?

I would suggest that you turn power off to the furnace, set the thermostat to OFF and turn the breaker on and off that sends power to the furnace. This might reset the error code.

Usually when you remove the "G" wire at the the control board and the fan continues to run it is a bad control board. It is usually a bad relay. Sometimes if you take the handle end of a screwdriver and tap the relay it will start working again. It is worth a try to at least identify that is the problem.
 

Last edited by firedawgsatx; 09-19-13 at 12:34 PM.
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Old 09-19-13, 12:31 PM
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Yeah, when I started, the wires were on the correct terminals. I switched them and noted no change - the LED still flashing at the high rate and the fan always on.

I've already tried turning power off from the breaker and thermostat and had the same result when turning back on - fan always running, and LED at the high rate.

I'll try switching the secondary terminals and see what happens.

Are there conditions in the unit that can cause the controller to command the fan on at all times? like some kind of detected condition with the burners? In the service manual for the unit, I haven't seen anything like that, but I'm still wondering why the controller seems to be activating the relay to turn the fan on (I can hear the click). I've seen relays fail where they welded on - with the observable characteristic that they don't click whether driven on or off. But here, a failure would have to be before the relay, like in the drive circuit or the microprocessor port. Rare in my experience.
 
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Old 09-19-13, 12:31 PM
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Not to confuse the issue..... but sometimes it's the incoming line.... not the transformer wires that are backwards.

On a Carrier unit....and open safety switch will keep the blower running but I think you mentioned the furnace is operating normally which means the safeties should all be ok.
 
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Old 09-19-13, 12:36 PM
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I had added a photo of your control board with some additional info to my last post. It is usually a relay problem. I have found that the error codes are a lot smarter than I am so it might just be the reversed transformer leads. I would try that.
 
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Old 09-19-13, 12:38 PM
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You mean the line coming from the house to the board? The black wire is going to the L2 terminal, and a white wire is going to the last of the N terminals - so it looks OK assuming the wires were properly connected from the house. Any idea how I can test this?
 
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Old 09-19-13, 12:50 PM
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Do you have a multimeter to check voltages. Did you get a chance to tap on the relay like I suggested in my previous post?
 
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Old 09-19-13, 12:53 PM
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That photo is exactly my board. I've already tried the tap on the relay trick, but I can clearly hear the relay click (and feel it, I put my finger on the housing of the relay when I pushed the door safety switch in) right as the fan turns on. However, I don't think it's the relay you've circled that I can hear click, but the one right next to it. I pulled the red wire from the control boards' terminal (marked "heat"), which is the wire going to the motor (marked "low" on the schematic). That caused the fan to not run. So I'm guessing that the control board is activating the relay for low speed fan operation all the time. This is with the thermostat in the "off" position on both the heat/cool switch and the fan auto/off switch.
 
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Old 09-19-13, 12:57 PM
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I do have a multimeter and did verify that 120VAC is at the primary of the transformer, and 24VAC is at the secondary.
 
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Old 09-19-13, 01:00 PM
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The relay next to the one I circled is for the medium speed for the blower motor.
 
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Old 09-19-13, 01:02 PM
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Check from ground to where the hot should be connected. Make sure there is actually 120v hot on the correct terminal.
 
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Old 09-19-13, 01:04 PM
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Huh, Well, since the two relays are close together, it's possible I was feeling the vibrations from the one you circled. I'll check again when I switch the 24V transformer leads.

Hey - found in the service manual a troubleshooting line for "Blower won't shut off". It says curreent leakage from controls into G,Y, or W and to check for a Triac switched t'stat or a solid state relay. Any idea what that is referring to?
 
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Old 09-19-13, 01:09 PM
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That means that one of the wires could be touching one of the other wires to energize another or a relay issue. One more thing: On the control board next to where the L2 terminal is there is the Primary Transformer terminals. Did you ever switch the wires on those two terminals?
 
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Old 09-19-13, 01:17 PM
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Yup, that's where I did the switch for the primary of the transformer - no change.
 
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Old 09-19-13, 01:24 PM
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The only other thing that I can think of is to inspect the 9-pin plug to make sure none of the pins are pushed back and not sending 24V to the relay. That 9-pin plug is where all of the rollout switches are connected in series. As you said the red and blue wires from the 24V side of the transformer go into the plug. If a relay does not receive the required 24V it can't open or close the contacts as required. On some furnaces loss of the 24VAC will keep the fan running continuously.
 
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Old 09-19-13, 01:27 PM
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Great suggestion - I'll check that at the same time I try reversing the secondary leads.
 
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Old 09-19-13, 01:32 PM
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Ok. I thought you had already switched the secondary leads. That might fix your problem. Also check the ground where it connects to the furnace chassis. A loose/corroded ground can cause a multitude of issues.
 
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Old 09-19-13, 10:59 PM
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Check all the grounds. The main ground coming in from the power line and the ground(s) to the control board.
 
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Old 09-20-13, 08:42 AM
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Well, I think a new control board is indicated.

Today, I checked:
- verified line in from house hooked up correctly
- Grounds on unit all good
- Swapped wires on the secondary of the transformer - same results, fan always on, fast blink LED
- 9 pin plug looked good - all pins in position, nothing loose, everything looks good when plugged in.

So a new control board is on the way and I'll update my results when I get it installed.

Thanks for all the help!
 
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Old 09-20-13, 09:53 AM
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I believe you did all you could to troubleshoot your issue. You said you verified line in from house was hooked up correctly. I found this thread that discusses the polarity issue. Check post #3: http://www.doityourself.com/forum/ga...-chapter2.html Yes, please do let us know the outcome and good luck!
 
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Old 09-25-13, 06:57 AM
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Well I installed a new control board and everything works as it should:

- fan only comes on when it should
- no more fast blinking LED

I did notice that the old control board had what looked like a blown electrolytic capacitor that caused some corrosion on the components below it. One of these is the driver IC for the relays. So that probably explains the fan always being on. I guess it'll stay a mystery as to why the old board thought the transformer polarity was wrong.

Thanks to all that helped!

Carl
 
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Old 09-25-13, 08:28 AM
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Thanks for the update

That IC and the circuit below it was the timing section. That may be also how they check phase.
 
 

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