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lkkuhl · 04-02-2017, 11:08 AM

Hello, all! We're new to RVs and recently purchased a 2003 Shasta Revere motor home. When we plugged it in to get everything charged up, the furnace blower came on and blows continuously(COLD air but the AC isn't on). We then turned on the propane and actually fired up the furnace, which works well, hoping that after the furnace went through a cycle, the blower would shut off. Well, it didn't. The furnace shut down, cooled off and still the blower runs.

Any suggestions how to resolve this? Thanks for any input and I hope to learn a lot from all of you experienced Rv-ers

RobbyII · 04-02-2017, 12:30 PM

Some MH's have a switch on the thermostat "Fan Only" or "Fan" that will run fan continuously. If you post the make and model someone will help out.

wingnut60 · 04-02-2017, 01:14 PM

Yes, sounds like your thermostat is on fan, indicated by the furnace does ignite, and shuts off, but the blower continues on.
Don't forget that if the furnace is ever turned on, there are several safeguards builtin to assure that the air is moving before the burner comes on--thus, the furnace will blow for a given time before the burner kicks on; also, ater it reaches thermostat temp, the burner will cut off, but the fan will continue til it cools the burner down.

Old-Biscuit · 04-02-2017, 01:25 PM

Fan position on thermostat is ONLY for FAN in A/C Unit.

Fan for furnace uses 12V DC and ONLY operates when thermostat calls for HEAT
Unless thermostat is BAD
Wires from thermostat to furnace are shorted
Circuit Board 'blower circuit' is BAD

So was it the A/C Fan that was running (fan setting on thermostat not in AUTO)

OR

Was Furnace fan running......see 3 causes above

ga traveler · 04-02-2017, 01:43 PM

You do not have a thermostat problem! The thermostat only supplies 12 volts to the furnace. If it were bad the furnace would not run or would never shut off the heat. Your furnace has a timer module for the fan. It runs the fan for thirty seconds before ignition to allow the fan to come up to speed so the air and gas are mixed correctly. It also causes the fan to run for two minutes after flame shut off, to allow the furnace to cool down and the combustion gases to clear from the combustion chamber. It is not turning off. This module is seperate from the main board. It is about 1X1 inch and black with four connections.

Old-Biscuit · 04-02-2017, 02:20 PM

Quote:

Originally Posted by ga traveler

You do not have a thermostat problem! The thermostat only supplies 12 volts to the furnace. If it were bad the furnace would not run or would never shut off the heat. Your furnace has a timer module for the fan. It runs the fan for thirty seconds before ignition to allow the fan to come up to speed so the air and gas are mixed correctly. It also causes the fan to run for two minutes after flame shut off, to allow the furnace to cool down and the combustion gases to clear from the combustion chamber. It is not turning off. This module is seperate from the main board. It is about 1X1 inch and black with four connections.

If thermostat is OFF---not calling for heat and is bad it can cause furnace fan to run continuously

If thermostat is OFF---not calling for heat and wires to furnace are shorted it can cause fan to run continuously

Depending on furnace model.....it can have a 'time delay relay' OR can be incorporated into circuit board---Blower circuit instead of the relay

Regardless.
Which Fan is running is REAL question
Fan wasn't running until 110V was connected.
Furnace (Fan) would be already running (12V DC) unless battery disconnect off

So was it furnace Fan OR was it A/C Fan???

**Spdracr39** · 04-02-2017, 03:00 PM

My thermostat has a fan on setting that will cause the fan on the ac to run continuously regardless of the temp and whether the compressor or furnace is on. The furnace blower is a separate fan. Are you sure it is the one that is running ?

ga traveler · 04-02-2017, 05:12 PM

[QUOTE=Old-Biscuit;3530586]If thermostat is OFF---not calling for heat and is bad it can cause furnace fan to run continuously

If thermostat is OFF---not calling for heat and wires to furnace are shorted it can cause fan to run continuously

#1 If that happened it would continually call for heat and the burner would not shut down. He said he heard the burner shut off, but the fan kept running.
#2 if he has a 12 volt short supplying the furnace, the burner would keep going as long as it receives 12 volts. Again he would not have heard the burner shut down. Some of the newer furnaces do have the timer circuit built in. It is possible it is the board.

lkkuhl · 04-03-2017, 08:58 AM

Well, my husband took the panel off of the blower compartment and found that there is an on/off switch on it. He shut it down while we were working in the RV, just because it was blowing cold air. But, obviously, it's going to have to be turned back on when we need the furnace/air, so is the blower running just something that we're going to have to deal with or does it have to be switched on and off anytime we need it?

4x4van · 04-03-2017, 10:28 AM

In addition to the temp setting, my thermostat has 3 switches; 1 for "Fan Mode" setting = AUTO or ON, 1 for "Thermostat" setting = COOL, OFF, or HEAT, 1 for "fan Speed" setting = HI or LO.

Quote:

Originally Posted by Old-Biscuit

Fan position on thermostat is ONLY for FAN in A/C Unit.

On mine, if the Fan Mode is "ON" (instead of AUTO) and Thermostat is on "HEAT", the furnace burner will cycle on or off to satisfy the temp setting, but the furnace blower fan motor WILL run continuously (either HI or LO depending on the Fan Speed setting, although the burner will force the fan to HI regardless of HI/LO setting).