Question about Rinnai RHFE-1004FA 38,400 BTU Energy Saver Ductless Heater - LP Gas

9 Answers

Rinnai 1004 - Temp on thermostat reads 10 deg cooler than actual, keeps running

My rinnai heater won't shut offf at the set temp. The built in Thermostat reads 10 degrees cooler than the actual room temperature. Any ideas?

Also, can an external thermostat be installed to be able to put a programmable thermostat on the unit?

Posted by on

  • 4 more comments 
  • Anonymous Dec 17, 2007

    I have the exact same problem with my 1004. Some days it will read 54 degrees in on the unit and its 65 in the house. I also have 431 in the same house with out the issue. my dealer said an add on thermostat, hard wire to the unit would solve the problem,,, it this true ?

  • Anonymous Dec 29, 2007

    Won't sut off. question if need a remote trermostat

  • Anonymous Jan 09, 2008

    I have the same problem, temp on thermostat reads 7-10 degrees coolerthan room temperature. I think thermistor should be monted higher in unit. It is basically mounted on the floor, which would be a cold area. Otherwise I love this heater, it is very efficient.

  • Anonymous Mar 16, 2014

    Whe I try to set the temperature above 66 degrees it gives a code of AOS

  • Anonymous Mar 26, 2014

    my Rinnai 1001f won't shut off once room temp is met. Please advise.

  • Thomas Long
    Thomas Long Jan 04, 2017

    I don't get any error code(s) but my Rinnai EX22CP was installed right beside my basement door, leaving the thermistor that senses the temperature near floor level and a small cold air leak. The installer said they could not install a thermostat elsewhere in the room (checked...Rinnai does not make one or allow for such). Finally having had it with the unit running too much when set to 62 deg.s, or not enough set at "Low", I read the install manual online and decided to relocate the thermistor (yellow twin lead wire to black thermistor) that sat near floor level at the back, left, of the unit. Although some have cautioned against "fooling with it", by cutting it off, leaving wire on each end to separate and strip (about 3/4"), splicing in a 6' twin lead 16 gauge lamp cord and relocating the thermistor away from the floor and cold air, the unit runs fine now. It runs less often, less "hard" and maintains an even temperature. Its setting does not match the thermometer near where I set the thermistor. If I set the unit to 66 deg.s, the room temp reads 68. Close enough for me. NOTE: I would not recommend this "Fix" to anyone who is not comfortable with electronics. I have quite a bit of electronics experience and read the install manual regarding the thermistor circuitry 1st! The thermistor's resistance should read between 10k and 100k Ohms. The lead I added reads in the milli-Ohms, insignificant change to the sensing circuitry. Too bad Rinnai can't just make a kit to extend the wiring and/or a thermostat to work with their units.



9 Answers

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Master
  • 1,420 Answers

Behind the unit near the floor level, is a yellow wire with a black bulb at the end. This is the actual sensor for returning air. If there is cool air infiltrating the area where it is located, it will keep the unit running until the return air reaches temperature. You could also have a bad sensor but highly unlikely. Make sure there is no air infiltration influencing the sensor. Also, you can unclip the sensor and pull out a few more inches of wire to locate it higher up away from the floor. Tie it up with a wire tie.

Rinnai it testing a remote thermostat but as of yet, there is no plans to offer one.

Posted on Nov 26, 2007


  • Level 1:

    An expert who has achieved level 1.


    An expert that has over 10 points.


    An expert whose answer got voted for 2 times.

    Problem Solver:

    An expert who has answered 5 questions.

  • Contributor
  • 12 Answers

The temp sensor on all Rinnai heaters are a yellow wire with a black bulb at the end of it. It measures the air behind the unit flowing through it. It is coiled up so that if necessary, it can be relocated outside of the chassis. This is a common problem with poor insulation in walls or poor installation. If the vent kit isn't sealed properly, cold air from the outside will cool the air behind the unit. Try moving the sensor to just outside the unit through the grates on the side, or make sure the vent kit is installed properly. It is a varible resistor, and VERY rarely fails. No, an external thermostat can't be installed since it measure resistance, and doesn't use a normal 24volt system to switch the heater on and off. If you could find a way to hook an external thermostat to the unit, you would undo what makes this unit so great. Self modulating heat control allows for more accurate temp control, and energy savings. The last thing you want is this unit turning on and off at high fire only.

Posted on Sep 14, 2009

  • 2 more comments 
  • NtenseZ71 Sep 14, 2009

    Cutting power to this unit is single-handedly THE WORST thing you can do for it. If you do this, you are stopping the heater from cooling itself down with it's circulation fan after the call for heat is complete. This WILL cause premature failure of the heat exchanger. Things are meant to be heated and cooled with the controller built into the unit. If Rinnai thought it was OK to put a thermostat on...they would have external thermostat connections. This unit carries a 10 year warranty on the heat exchanger because it has a computer inside to monitor the temperature and protect it. Altering this will be an easy way to void this warranty, and kill the unit.

  • NtenseZ71 Sep 14, 2009

    If you fire up your heater and let it warm up, then turn the POWER button on the unit'll notice the fan continues to run even though the display is not on anymore. They did this for a reason...

  • NtenseZ71 Sep 14, 2009

    P.S. Cutting and altering the length of the wire will effect the unit. Since it is a Thermister (a temperature sensor that varies resistance with temp change) adding wire to the system increases the resistance in the circuit. Every inch of wire carries a pre-defined amount of resistance. Therefore, (hypothetical numbers), if 80 degrees were to be 1.2 ohms, adding additional resistance would alter the reading of the unit. IF you increased that to 1.3 ohms, the unit would think it was 78 degrees.

  • Thomas Long
    Thomas Long Jan 04, 2017

    The thermistor runs (at around room temperature) between 10k and 100kOhms. I add about 6' of 16 gauge wire to relocate the thermistor where it would sense room temperature rather than floor temperature. The 6' or so of wire adds, maybe, a few milli-Ohms of resistance and varies insignificantly with temperature at room temp. The "fix" works fine but I would not recommend unless comfortable with electronics (likely voids warranty too but I'll take that over too hot or too cold and the unit running too hard). TRL - ASEE/BSEE


  • Level 1:

    An expert who has achieved level 1.


    An expert whose answer got voted for 2 times.

  • Contributor
  • 2 Answers
  • Level 1:

    An expert who has achieved level 1.

    New Friend:

    An expert that has 1 follower.

  • Contributor
  • 1 Answer

Definitely the thermostat location. My Rinnai is located right next to the entrance door of my house in the Adirondack mountains. Even when the house is at 70 degrees, the heater reads 62. The thermostat bulb is located in the rear of the bottom right corner of the heater, near the floor. (I have an unheated crawl space) This is probably the coldest spot in the house. Simply relocating the bulb solved the problem.... Simple and easy.. Hope this helps...

Posted on Feb 23, 2013

The location of the sensor needs to be higher but my yellow wire would only pull out a couple of inches.
Turn off power to unit and remove front panel. Two screws near top/sides. Top of panel pulls out (unplug wire connector to indicator lights) and lifts off bottom tangs. Now you will see a coil of yellow wire inside unit. Remove the wire tie and you'll have enough yellow wire to locate the sensor well above the heater.

Posted on Dec 31, 2007

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 2 Answers

I think and will test later.... YES....

Its seem that its just like my pellet stove.

take a low voltage thermostat you STILL need the THERMISTOR the little black bulb/senser at end of yellow wire....

wire it as follows.....

Thermostat wall mounted
you have 2 wires coming from that let's say red and black for this talk.

red wire runs from wall mounted thermostat to back of heater
black wire runs from wall mounted thermostat to one side of yellow wire then other side of yellow wire to back of heater basiclly put the THERMISTOR inline.

Set thermostat.... to temp... you will most likey get and error or blinking light while the thermostat is NOT calling for heat. Once the thermostat calls for heat the error should clear and heat should come on.

Set the temp in the 1004F for highest setting.... I'm not going to be able to test for a few days but I think this should work.... let me know if you beat me to it...

Posted on Jan 14, 2010

Had just purchased and installed the 1004FA to my garage which we are in the middle of converting to a play room. I must say that the unit operates fine with the exception that the unit registers ~ 7 deg lower that the actual room temp. I then came to a solution of moving the thermistor... cut and stripped the yellow wire and respliced the thermister to about 8 feet away on the same wall. Now the unit opererates fine and shuts down when the set temp is met. It was easy since the walls are open and wiring is hidden.

Tried to connect a programmable thermostat but its a no go. The heater does not like when the thermister is in an open condition and the main readout on the units control bourd blinks that there is a problem with the thermister. I'd like Rinnai to come out with an adapter for the unit to operate on a programable thermostat it would be a huge plus.

Posted on Feb 13, 2008

Make sure there is no cold air at the location of sensor. My unit is located on a out side wall and under the floor is not insulated therefor the unit runs until the floor is up to temp. This unis works fantastic but should be able to adapt nto a wall thermostat.

Posted on Dec 02, 2007

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 2 Answers

Check out the LUX PSP300 outlet programmable thermostat. This thermostat is plugged into the electric outlet, and the Rinnai is then plugged into the thermostat.The LUX is a full featured thermostat that includes an adjustment of +/= 5degrees F for its base temp reading.It controls the appliance by cutting power. When the Rinnai 1004 powers back up after power interuption it will be set at its default temp setting of 70 degrees F. For most applications this works great as the location of the temp sensor on the Rinnai means you should not need a setting above 70 degrees F.I purchased mine from for $45.00. Hope this helps......

Posted on Nov 08, 2008

1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

A 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
The service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Good luck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

Rinnai Avenger 25...Thermostat is on 26 but the room is no where near that hot??

the heater will attempt to heat the room until temp is reached if door is opened or cool air enters the heater will continue to run if the heater is set to 20 when the room reaches 20 the heater will shut down until temp drops below 20 then restart

Jun 12, 2011 | Rinnai Heating & Cooling

1 Answer

I have had my Rinnai tankless for about 8 years without problems. Recently I am noticing that the water temperature is fluctuating from the set temperature to a cooler temp and then back up to the set...

The Rinnai will shut off it can't maintain the temperature you have set to within +/- 3 degs so I'd guess that might be the problem. The cause can be a few options. Check water flow first; any filters you have in tapware, main water flow etc. get cleaned. The Rinnai has a water line filter in the incoming supply, middle pipe under the heater just after the isolating valve. Gas supply could be the other option mainly being a possible intermittent fault in the gas regulator. Hard to check this one short of just changing it. Final option is some sort of electronic malfunction, pretty rare. I'd start with the water flow issue as you can do this yourself. Checking the gas will need a good technician with digital gas pressure guage to check incoming and working gas pressures; it might just need to be recalibrated. Just hasd a thought about the heat exchanger being scaled up if you are in an arera where water scale is a problem but this would normally take far less than 8 years to be a problem. Sorry can't be of more help; hard when it might be a few different causes.

May 28, 2011 | Rinnai Water Heaters

1 Answer

MY RINNAi will not shut itself off, continues to run no matter what temp I set it at.

The thermostat wire is located near the floor, so it is possible there is a draft where it is located causing the heater to continually run. I turned the power off to my heater and took the front and side panel off. The thermostat wire is yellow and runs to the back. At the end of the wire is a black bulb like structure. The yellow wire is typically coiled up with extra wire. I undid the coil and re routed the wire and bulb end up to the top of the heater. Works much better now.

Jan 15, 2011 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

1 Answer

When the temp drops below 10degrees our Rinnai

rinnai has a technical bulletin out on this condition #28. It instructs the technician to adjust the gas pressure. You can get a copy of this bulletin by contacting rinnai at 800-621-9419 (US). or at

Feb 02, 2010 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

1 Answer

Have a 1004fa model to heat a room. temp on

You may have a bad circuit board. Depending upon the age of the heater it may still be under warranty. Contact Rinnai (in US) 800-621-9419 with your serial number and installation date. Ask if they can offer a solution. Good Luck!

Jan 13, 2010 | Rinnai Heating & Cooling

1 Answer

Only staying in house once in a while, when I turn down the Rinnai 10011, at lowest temp. setting it's still too warm (60deg.) Don't need more than 45 deg. or so, just to keep from freezing pipes. Don't...

You will need to locate a lower temperature range thermostat.The thermostat you have allows a range that is more in line with the "human comfort" range, which is 60-90 or so degrees.
You will probably not be able to get a stat that will replace the one in the Rinnai.
I cannot find the model number you've indicated on the Rinnai website to help you further.

Dec 14, 2009 | Televison & Video

1 Answer

Rinnai 1004 heats to a temp 4 degrees higher than set temp, adjustment?

You can adjust the position of the room air sensor found on the back of the unit between the heater and the wall. It is a black rubber bulb with yellow wires. There is a few inches of extra wire you can extend higher to get a more accurate reading of room air. While you are back there, check for drafts that will give you false readings.

Sep 23, 2008 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

2 Answers


It is found in the lower right hand corner of the heater (as facing from the front) behind the trim pieces close to the wall. It will be a yellow wire with a black plastic tip. Prior to replacing it, Hold it in your hand and see if the heater shuts off after a minute or so. If it does, seal the area behind the heater for air leaks and raise up the sensor closer to the top of the heater. There is slack in the wire if you remove the front cover of the heater and undo a tie holding the excess wire. If holding on to the sensor does not help, check the connection on the circuit board. Replace it if it does not help. Part nuber 1004F-2057.

Dec 08, 2007 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

2 Answers

Power reset - Rinnai 1004

the rinnai is like a monitor. just unplug it, wait five min and plug it back in. then radjust your temp set point and it should pick back up. when there is a power outage the led-s flash 88:88

Nov 17, 2007 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

3 Answers

Rinnai RHFE-1001FA

I can suggest a around-about solution. I also have the same model installed around the same time. I have the outlet that it is connected to controlled by an electric heat thermostat on a wall at the oposite side of the room. I keep the heater on high at all times and the thermostat controls the electricity to the outlet. It's worked great for the 13 years it's been installed.

Mar 11, 2007 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

Not finding what you are looking for?
Rinnai RHFE-1004FA 38,400 BTU Energy Saver Ductless Heater - LP Gas Logo

8,072 people viewed this question

Ask a Question

Usually answered in minutes!

Top Rinnai Heating & Cooling Experts

Paul Carew

Level 3 Expert

3182 Answers

Dan Webster
Dan Webster

Level 3 Expert

8220 Answers

vance jones

Level 2 Expert

120 Answers

Are you a Rinnai Heating and Cooling Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides