Trouble light blinks 4 times on White Rodgers 50T35-730 with Goodman GMP 075-3
#1
12-28-13, 10:38 AM
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Trouble light blinks 4 times on White Rodgers 50T35-730 with Goodman GMP 075-3
We would be grateful for any help.
Goodman GMP 075-3 is dated 1993.
2 months ago, I installed a White Rodgers 50T35-730 control board.
We live in GA.
Temperatures are running 30s & 50s right now.
HISTORY:
Just in case it may be related, I'll add that 2 months ago we were getting a 3 blink trouble. I ordered a control board & installed. That didn't work. I then figured out by blowing through the little air hose that the little tit on the small blower was clogged with dirt (found a dirt dobber nest in the small vent pipe). That was causing the pressure switch to malfunction. Thanked God big time for fixing it! I elected to keep the new control board in place & it worked fine thereafter.
TODAY:
The unit was heating until mid-morning today. The wife noticed a strange smell with no heat coming from the vents. I went to look at the unit & discovered the trouble light blinking 4 times. I powered it off & then back on. It went through the cycles with the last one being flames on. After the flames were blowing for about 20 seconds, I hear a click but nothing else cycles on (I believe it should be the large blower). After another few seconds, the flames cut off & the light starts blinking 4 times.
As I understand what I'm reading in my paperwork & these forums, it would indicate an "open limit switch". I see in my paperwork that this unit has both a "limit switch, 160,7" and an "auxiliary limit control".
I don't know what to do from here. Not sure how to tell if it's the "limit switch" or "auxiliary limit control" that's bad. Or if it's an indication that the large blower is bad. I'm not an electrician or hvac guy, just a guy who tries to figure it out as we can't afford other options.
Goodman GMP 075-3 is dated 1993.
2 months ago, I installed a White Rodgers 50T35-730 control board.
We live in GA.
Temperatures are running 30s & 50s right now.
HISTORY:
Just in case it may be related, I'll add that 2 months ago we were getting a 3 blink trouble. I ordered a control board & installed. That didn't work. I then figured out by blowing through the little air hose that the little tit on the small blower was clogged with dirt (found a dirt dobber nest in the small vent pipe). That was causing the pressure switch to malfunction. Thanked God big time for fixing it! I elected to keep the new control board in place & it worked fine thereafter.
TODAY:
The unit was heating until mid-morning today. The wife noticed a strange smell with no heat coming from the vents. I went to look at the unit & discovered the trouble light blinking 4 times. I powered it off & then back on. It went through the cycles with the last one being flames on. After the flames were blowing for about 20 seconds, I hear a click but nothing else cycles on (I believe it should be the large blower). After another few seconds, the flames cut off & the light starts blinking 4 times.
As I understand what I'm reading in my paperwork & these forums, it would indicate an "open limit switch". I see in my paperwork that this unit has both a "limit switch, 160,7" and an "auxiliary limit control".
I don't know what to do from here. Not sure how to tell if it's the "limit switch" or "auxiliary limit control" that's bad. Or if it's an indication that the large blower is bad. I'm not an electrician or hvac guy, just a guy who tries to figure it out as we can't afford other options.
#2
12-28-13, 11:29 AM
Group Moderator
Welcome to the forums.
It sounds like you have a blower issue. If you have a FAN ON position on the thermostat.... try that first.
If that doesn't help.... you'll need to turn off the power to your furnace. Remove the bottom service cover and check and see if the blower/motor is frozen. It should spin smoothly. If not it will need to be replaced.
If it spins freely, you can put the thermostat in FAN ON, turn power back on to furnace, hold in service door safety switch and using a stick or a thin piece of wood.... carefully try spinning the blower. If it starts then it may need a new starting capacitor.
It sounds like you have a blower issue. If you have a FAN ON position on the thermostat.... try that first.
If that doesn't help.... you'll need to turn off the power to your furnace. Remove the bottom service cover and check and see if the blower/motor is frozen. It should spin smoothly. If not it will need to be replaced.
If it spins freely, you can put the thermostat in FAN ON, turn power back on to furnace, hold in service door safety switch and using a stick or a thin piece of wood.... carefully try spinning the blower. If it starts then it may need a new starting capacitor.
#3
12-28-13, 12:23 PM
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You sir are wonderful. You nailed it.
I tried the "fan on" but it didn't come on. Reached in & the blower spun by hand.
Then I remembered a few years back that we picked up what I call a "capacitor booster" for an issue with our outside a/c unit which we only used temporarily. I went digging & found it. It's a Diversitech Hard Start part. I knew I was holding on to it for some reason.
Anyway, I connected it & it worked. I assume the right thing to do is go get a replacement capacitor & then I'll hold onto that booster for next time.
I really appreciate your input & what you bring to this forum. You are a blessing.
http://youtu.be/o-WkmiwrbEk
I tried the "fan on" but it didn't come on. Reached in & the blower spun by hand.
Then I remembered a few years back that we picked up what I call a "capacitor booster" for an issue with our outside a/c unit which we only used temporarily. I went digging & found it. It's a Diversitech Hard Start part. I knew I was holding on to it for some reason.
Anyway, I connected it & it worked. I assume the right thing to do is go get a replacement capacitor & then I'll hold onto that booster for next time.
I really appreciate your input & what you bring to this forum. You are a blessing.
http://youtu.be/o-WkmiwrbEk
#4
12-28-13, 12:48 PM
I'd replace that booster asap. It was designed for a compressor, not a blower motor. Glad it wasn't a motor, but if you continue to use that, it may be a motor sooner than later.
#5
12-28-13, 04:47 PM
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Tinmantu is right...... you'll want to replace that capacitor with the proper one ASAP. That's listed as a run capacitor and can cause the motor to overheat.... shortening its life considerably.
#6
12-28-13, 05:32 PM
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Understood. Based on the capacitor description in my manual & the current capacitor that is there now, I believe the right one is at Grainger which I can pick up early Monday morning. Does it look right to you? DAYTON Run Capacitor,12.5 MFD,370 VAC,Oval - Capacitors - 2MDV8|2MDV8 - Grainger Industrial Supply
The book list it as "capacitor, 12.5/370" whereas the old one there now is this one https://www.dropbox.com/s/4bs8snmfwf...%2036%20PM.jpg
The book list it as "capacitor, 12.5/370" whereas the old one there now is this one https://www.dropbox.com/s/4bs8snmfwf...%2036%20PM.jpg
#7
12-28-13, 06:07 PM
If that's what the specs of the motor call for, I guess it's right. Most motors I've installed over the years went from 5-7.5, rarely 10. Have to admit, I'm a little surprised to see 12.5
#8
12-28-13, 10:24 PM
Group Moderator
You'll definitely want to use what was in there previously. I can't verify from the service manual since it includes like 10 different capacity units.
If there was a question on the size..... you could check on the motor also.
If there was a question on the size..... you could check on the motor also.
