Coleman 7680B Furnace Won’t Shut Off
Posted: Thu Mar 19, 2009 3:15 am
Hi,
We just bought this manufactured home in February and I’ve got a Coleman furnace which acts weird. When the temperature is 45 degrees or below outside, the furnace won’t shut off. However, when the outside temperature is in the 50’s, it will operate correctly. I thought it was the old White/Rogers mercury type thermostat which was bad, so I bought the LUX DMH110 thermostat and I’m pretty sure I connected the 4 wires correctly as I labeled them and followed the simple instructions.
The thermostat is set to FAN-AUTO and to HEAT. I set the thermostat to 73 and it operates correctly for several hours but then it goes crazy. About 2 or 3 in the morning (colder outside) it will come on and won’t shut off. A few weeks ago I thought I woke up in hell because the temperature hit 88 degrees!
Also, when I go to the thermostat and turn the MODE SWITCH to OFF.. nothing happens. I have to shut off the blower/motor at the wall mounted switch next to the furnace. Also, many times if I pull the cover of the thermostat off and press the RESET switch then reset the temperature to 73 the furnace will operate correctly for a few cycles then won’t shut off. By the way, this same condition was happening with the old W/R thermostat and that is why I thought it was the thermostat.
My wife usually goes to bed at 10:00 p.m. and I’m a night owl. I’m also retired as I’m home 90% of the time. Sooooo, the way we’ve been operating is we let the furnace run and when it operates correctly we’re happy. Then, when I go to bed about 4:00 a.m., I turn the blower/motor off and when she gets up at 6:00 a.m. the house is cold so she turns it on for a couple of hours prior to going to work.. then shuts it down for me so I won’t go to (you-know-where) again before I wake up.
Last week I shut the unit down completely. I turned off the power at the circuit breaker. Turned off the gas, and opened up the “A” coil box and used a powerful light and inspection mirror. The coils looked clean and I could see no problem.
I really need your help and I sincerely appreciate it. I’ve read through most of the other posts but couldn’t find a specific answer to this weird problem. Below are the particulars on this Coleman unit.
Bless you and thanks for your good help.
Coleman Mobile Home Furnace
Model No. 7680B Series 856
Serial No: 087764567
Fan Switch: F120-3 770-328
2601F134-191 L7V
Lower Limit Switch: L155-2 7680-359
20601L9-718 L7V
Evcon 4-Wire Thermostat A/C Control Box
Number: 7900A6041
GE Capacitor: Z97F9001
Outside Unit is:
Coleman/Evcon Heat Pump
Model No. BRHS036B
Serial No: 940405857
DMH110 Thermostat Wiring:
» Y wire to Y connector.
» W wire to W connector.
» RH to RH connector.
» G to G connector.
» Jumper from RH to RC is ON (Factory Setting. I took it off but it didn’t help so I put it back on).
JP1 is Closed (5 Minute Minum run/Off Time – Factory default)
JP2 is Closed (Fahrenheit Display Format)
JP3 is Open
JP4 is Open (Gas/Electric fan operation). As this is a gas furnace, the instructions said: “Choose gas if you have a gas heating system, this will allow the furnace itself to control the operation of the blower fan.”
(Note, I opened JP3 to change the swing and the furnace/blower operated better but after a few cycles it still will not shut off).
We just bought this manufactured home in February and I’ve got a Coleman furnace which acts weird. When the temperature is 45 degrees or below outside, the furnace won’t shut off. However, when the outside temperature is in the 50’s, it will operate correctly. I thought it was the old White/Rogers mercury type thermostat which was bad, so I bought the LUX DMH110 thermostat and I’m pretty sure I connected the 4 wires correctly as I labeled them and followed the simple instructions.
The thermostat is set to FAN-AUTO and to HEAT. I set the thermostat to 73 and it operates correctly for several hours but then it goes crazy. About 2 or 3 in the morning (colder outside) it will come on and won’t shut off. A few weeks ago I thought I woke up in hell because the temperature hit 88 degrees!
Also, when I go to the thermostat and turn the MODE SWITCH to OFF.. nothing happens. I have to shut off the blower/motor at the wall mounted switch next to the furnace. Also, many times if I pull the cover of the thermostat off and press the RESET switch then reset the temperature to 73 the furnace will operate correctly for a few cycles then won’t shut off. By the way, this same condition was happening with the old W/R thermostat and that is why I thought it was the thermostat.
My wife usually goes to bed at 10:00 p.m. and I’m a night owl. I’m also retired as I’m home 90% of the time. Sooooo, the way we’ve been operating is we let the furnace run and when it operates correctly we’re happy. Then, when I go to bed about 4:00 a.m., I turn the blower/motor off and when she gets up at 6:00 a.m. the house is cold so she turns it on for a couple of hours prior to going to work.. then shuts it down for me so I won’t go to (you-know-where) again before I wake up.
Last week I shut the unit down completely. I turned off the power at the circuit breaker. Turned off the gas, and opened up the “A” coil box and used a powerful light and inspection mirror. The coils looked clean and I could see no problem.
I really need your help and I sincerely appreciate it. I’ve read through most of the other posts but couldn’t find a specific answer to this weird problem. Below are the particulars on this Coleman unit.
Bless you and thanks for your good help.
Coleman Mobile Home Furnace
Model No. 7680B Series 856
Serial No: 087764567
Fan Switch: F120-3 770-328
2601F134-191 L7V
Lower Limit Switch: L155-2 7680-359
20601L9-718 L7V
Evcon 4-Wire Thermostat A/C Control Box
Number: 7900A6041
GE Capacitor: Z97F9001
Outside Unit is:
Coleman/Evcon Heat Pump
Model No. BRHS036B
Serial No: 940405857
DMH110 Thermostat Wiring:
» Y wire to Y connector.
» W wire to W connector.
» RH to RH connector.
» G to G connector.
» Jumper from RH to RC is ON (Factory Setting. I took it off but it didn’t help so I put it back on).
JP1 is Closed (5 Minute Minum run/Off Time – Factory default)
JP2 is Closed (Fahrenheit Display Format)
JP3 is Open
JP4 is Open (Gas/Electric fan operation). As this is a gas furnace, the instructions said: “Choose gas if you have a gas heating system, this will allow the furnace itself to control the operation of the blower fan.”
(Note, I opened JP3 to change the swing and the furnace/blower operated better but after a few cycles it still will not shut off).