Nov 03, 2018 Water is collecting on the shelf the circuit board is sitting on and short circuits the components on the board causing the fan to run constantly regardless of the position of the thermostat. Blower fan runs all the time even when furnace is off. Everything else works just fine. Blower does not turn off - Answered by a verified RV.
- POST a QUESTION or READ FAQs about diagnosing furnace fan operating problems
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Forced air heating or cooling air handler troubleshooting: blower fan won't shut off:
This article describes what to check if the furnace or forced air blower fan does not stop when you expect it to do so.
These same diagnostics also aid in air conditioning blower assembly diagnosis when an A/C blower continues running. We explain what switches or controls may be set improperly or what else, such as a shorted wire, can cause continuous HVAC fan operation.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
What to Check if your Furnace Fan or Air Handler Blower Fan Runs Continuously
These diagnostic steps are for an air handler, blower, or furnace fan that just won't quit running.
Other heating system problems that can cause a furnace (or boiler) to refuse to stop are given
at HEAT WON'T TURN OFF.
First, confirm that the room thermostat is not calling for heating or cooling.
In the heating season, just set the thermostat(s) to the lowest setting and confirm that room temperature is above that point. In the cooling season do the opposite - set the thermostat to its highest setting and confirm that room temperature is below that point.
You have told the thermostat to turn off the HVAC equipment.
If the equipment was running give it three to four minutes to shut down.
Next: If the blower just keeps running no matter what, there are two places to check switch settings before calling your heating or air conditioning service company in response to a furnace fan or air conditioning fan that just keeps running without stopping:
1. At the room thermostat: the FAN-AUTO-OFF or FAN ON/OFF switch on the room thermostat should be checked.
The fan control should be set to AUTO. You can try turning the switch to OFF too.
Details of checking the thermostat's FAN-AUTO-OFF or FAN-ON switch position when the furnace (or air conditioning) fan won't stop running are
Details of checking the thermostat's FAN-AUTO-OFF or FAN-ON switch position when the furnace (or air conditioning) fan won't stop running are
at FAN WONT STOP - THERMOSTAT SWITCH
Other snafus such as a shorted thermostat wire can also cause the A/C or warm air furnace fan to run continuously.
Other snafus such as a shorted thermostat wire can also cause the A/C or warm air furnace fan to run continuously.
Those problems are explained at THERMOSTAT WON'T TURN OFF.
2. At the furnace or air conditioner air handler or blower unit: the fan limit switch may include a switch that manually keeps the fan running.
We discuss this switch right here. If you don't know where to find the limit control switch on your furnace or air handler,
see FAN LIMIT SWITCH.
Some models of Fan Limit Controls such as the Honeywell L4046B229& Universal Fan and Limit Controler, in particular the Honeywell L4064B,W, and R models have a manual fan switch that overrides the fan control to keep the fan running continuously. The white knob and white arrow in our photo point to this manual fan switch.
Some models of Fan Limit Controls such as the Honeywell L4046B229& Universal Fan and Limit Controler, in particular the Honeywell L4064B,W, and R models have a manual fan switch that overrides the fan control to keep the fan running continuously. The white knob and white arrow in our photo point to this manual fan switch.
Take a look at the fan limit control switch. Before pulling the cover off of the switch, just see if the switch includes a control such as the white push-pull switch like the white device shown at the lower left in our photo.
Depending on the position of this switch (pushed-in or pulled out) the fan may be on manual override - causing the fan motor to run continuously.
Check the printing on the switch face to see if you should push the switch in or pull it out to leave the blower on 'Auto'. ('Man' or 'Manual' would be forcing the fan to run.)
Which way to set the manual furnace or air conditioner blower fan switch:
Usually: 'Push-in' position on this (Honeywell) fan limit switch is for continuous fan operation and 'Pull out' position is for automatic fan operation.
There are some reasons (explained at BLOWER FAN CONTINUOUS OPERATION) to leave the blower fan on continuously for long periods, such as to use an air filtering system to improve indoor air quality.
![Furnace Furnace](https://i.ytimg.com/vi/fxRB4MVFOuo/maxresdefault.jpg)
And in some buildings we may run the blower continuously for more even or better conditioned (heated or cooled) air distribution.
What Else to Check if the Blower or Furnace Fan Won't Stop
On the off chance that someone has inadvertently mis-connected or shorted fan control wires at the fan limit switch, also check
out FAN LIMIT SWITCH INSTALLATION & WIRING.
On the chance that there is a shorted thermostat wire, a problem that can also cause the A/C or warm air furnace fan to run continuously
see THERMOSTAT WON'T TURN OFF.
Details about the manual FAN ON or FAN AUTO ON switch right at the furnace or air handler at the manual
at BLOWER FAN CONTINUOUS OPERATION.
This article series answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs.
We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.
Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Reader Question: Furnace fan keeps running with no heat coming from the furnace
2015/10/22 Anonymous said:
My fan keeps running with no heat on furnace. What can I do?
Reply: 6 steps to getting heat on when the fan runs but the furnace does not
If the furnace does not even try to run, that is if it never even starts, then follow these steps:
- Check the thermostat settings to be sure that you are calling for heat (set-temperature is above room temperature).
See THERMOSTATS, HEATING / COOLING - home - Check that the thermostat FAN switch is set to AUTO not to ON.
See THERMOSTAT SWITCHES, EXTERNAL - Check that the manual FAN ON switch at the fan limit switch in the furnace or air handler is not in manual ON position.
See FAN LIMIT SWITCH for details. - Check the furnace primary controller to see if the 'reset' button on the control (or on the burner motor) has popped out - you can try pressing the switch in ONCE but don't keep pressing it as doing so is unsafe.
For oil fired furnaces see RESET SWITCH - HEAT CONTROL
or see RESET SWITCH, CAD CELL RELAY
or on older furnaces see STACK RELAY SWITCH
For electric motor reset switches that are present on some (not all) oil burners
see ELECTRIC MOTOR OVERLOAD RESET SWITCH
For gas fired furnaces
see SPILL SWITCH, FLUE GAS DETECTOR; other defects such as a bad thermocouple can keep the gas burner from igniting or burning.
For gas burner thermocouple problems
see THERMOCOUPLES - Check for voltage at the oil burner primary control. This is a simple test to see that power is actually being delivered to the oil burner control. You can use a neon tester, a VOM, DMM, or a voltage detector stick.
Watch out: if you are not expert in safe use of electrical test tools you could be electrocuted - killed. Call an expert.
See VOLTS MEASUREMENT METHODS - Check for a bad primary control: If there is voltage to the primary control, no reset buttons are popped, and the thermostat is calling for heat (check that right at the primary control thermostat wires) then I suspect a bad primary control unit itself.
At that point your heating service tech will perform her own tests and then if needed repair wiring or replace the furnace control.
Oil heat: see CAD CELL RELAY SWITCH
or
Gas heat: see the gas furnace controls cited above at step 4.
If the furnace tries to start but cannot keep running then there is a different problem such as no fuel or an unsafe condition.
See DIAGNOSE & FIX HEATING PROBLEMS-FURNACE - home
A complete list of oil and gas fired furnace controls is
at FURNACE CONTROLS & SWITCHES
at FURNACE CONTROLS & SWITCHES
...
![Fan Fan](http://i1128.photobucket.com/albums/m481/strey2/WAVE%206%20INSTALL/100_4312_zpsec7add90.jpg)
Continue reading at FAN WONT STOP - THERMOSTAT SWITCH, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see FURNACE FAN WONT STOP FAQs - questions & answers about why the furnace blower fan won't stop running
Or see these
HVAC Blower Fan Articles
- AIR HANDLER / BLOWER UNITS - home
- BLOWER FAN OPERATION & TESTING - home
- FAN LIMIT SWITCH - home
- HEAT WON'T TURN OFF for other reasons that a heating system won't stop running
- UNDERSIZED RETURN DUCTS - not enough return air
Suggested citation for this web page
FURNACE FAN WONT STOP at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING FURNACES
Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia
Share this article
...
Ask a Question or Search InspectApedia
Search the InspectApedia website
Please enable JavaScript to view the comments powered by Disqus.Technical Reviewers & References
- [1] ...
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
- Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
- ...
- Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: [email protected]. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page 'Promo/Redemption' space. - TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page 'Promo/Redemption' space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
- The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page 'Promo/Redemption' space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page 'Promo/Redemption' space.
Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd - Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page 'Promo/Redemption' space. InspectAPedia.com editor Daniel Friedman is a contributing author. - The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones
Recreational Vehicle (RV) furnaces always seem to malfunction just when you need them the most. If you are having problems with your RV furnace, you do not want to have to take the vehicle in to have it serviced. You want the problem fixed immediately. Some RV furnace troubleshooting tips can help you to better understand how your RV furnace works and can give you some ideas on how to repair it yourself.
How an RV furnace operates
If the thermostat in your RV controls both the air conditioner and the furnace, be sure the switch is set on 'Heat.' If the thermostat in your RV controls only the furnace, then turn the setting to the 'On' position. When you raise the thermostat to a warmer temperature, the furnace blower will turn on after about 30 seconds. The furnace blower must run for 30 seconds after it comes on for the burner to fire up. It is perfectly normal for the burner to continue to cycle on and off while the furnace is running. When the RV reaches the desired temperature, the burner will shut off, but the blower will keep running for a little while longer.
The pilot light will not light
If the pilot light on your RV furnace will not light, check that the thermocouple is correctly positioned in the pilot flame. The problem could also be that the propane tank has a bad regulator. You can test for a bad regulator by lighting all the stove burners and examining the color of the flames. They should be a bluish color and contain little or no yellow. If the flames change colors, the regulator is most likely bad. The regulator will need to be repaired because a bad regulator will also affect the hot water heater.
The fan runs but there is heat
If the fan on your RV furnace runs but there is heat, the problem could be that the furnace has an insufficient air flow. The propane tank could also have a bad regulator or there might be a bad propane valve. Furnaces have internal switches that can detect air flow. If there is insufficient air flow, the switch will not let the furnace ignite, and the fan runs but there is no heat. There could also be a low battery, a bad wiring connection, or a restricted ventilation system. Examine the heat registers to see if they are blocked or closed. Some RV furnaces will not operate if the heat registers are even partially closed.
The fan does not run and there is no heat
If the fan on your RV furnace does not run and there is no heat, check the battery with a battery tester. If the battery is putting out at least 12 volts, then the battery is fine. You might have just tripped the circuit breaker, so try resetting the circuit. The problem could also be a blown fuse on the fan. Replacing the fuse should get the fan running again.