Question about Mr. Heater MHU45NG

1 Answer

3 flashes, won't ignite. Natural gas is on and good pressure through line. Manual says that pressure switch malfunction of some sort. Any ideas what to do?

I have never used heater as it was installed new in the shop that I just purchased so I do not know how much it has been used.

Posted by on

1 Answer

  • Level 1:

    An expert who has achieved level 1.

    Hot-Shot:

    An expert who has answered 20 questions.

    Corporal:

    An expert that hasĀ over 10 points.

    Mayor:

    An expert whose answer gotĀ voted for 2 times.

  • Contributor
  • 51 Answers

Check the setting of the control valve and make sure it is not set up for LP gas. Check the pressure switch with a meter and make sure the NO and NC connections read correctly.

Posted on Jan 01, 2013

4 Suggested Answers

6ya6ya
  • 2 Answers

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

Hi,
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.
goodluck!

Posted on Jan 02, 2017

kentguidry
  • 51 Answers

SOURCE: MHU45LP won't fire

The pressure switch to which you are referring is the switch connected to the suction side of your induced draft fan. This pressure switch will have a hose connected between the switch and the induced draft fan. Please let me know if you need any more assistance.

Posted on Feb 17, 2009

  • 1 Answer

SOURCE: Mr. Heater Natural Gas Garage Heater - 45,000 BTU.

my garage heater was working early this winter. I turned the thermostat to 0, but when I went to restart heater nothing happens, can you help me with this problem?

Posted on Dec 27, 2009

Therinnaiguy
  • 1420 Answers

SOURCE: we have a 75,000 Natural Gas Mr.Heater

Make sure you are using the R and W terminals both at the heater as well as at the thermostat. Try jumping the wires together without the thermostat and see if the unit starts. If it does, bad thermostat. If you continue to get the error code, you may have a bad board.

Posted on Jan 16, 2010

Add Your Answer

Uploading: 0%

my-video-file.mp4

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

×

Loading...
Loading...

Related Questions:

1 Answer

I have a Big Maxx heater and it won't stop blowing and won't heat. The fan just keeps running! Anyone know what could be wrong?


Your pressure switch may not be activating (ie closing and making contacts) This means you could have a blocked flue, clogged pressure switch tube or a bad pressure switch. The pressure switch is a safety feature to ensure your exhaust is not blocked and operating correctly. Find owners manual. Look at trouble shooting section. Open cabinet and look for error code light. If blinking 3 times, try "jumping" the pressure switch. To jump pressure switch you need to clear code be turning off power. When the unit/thermostat calls for heat the power vent fan starts first, this is when you need to jump the pressure switch. You need to do this in sequence. That is the unit first starts the power vent exhaust thus activating the pressure switch allowing the ignition cycle to the burners and heat. So the power vent fan needs to start first BEFORE you put the jumper on to bypass the pressure switch. Once the jumper is on it will call for ignition after approx 30 seconds. If ignites your problem is one of the 3 stated at the opening of this paragraph

Mar 21, 2013 | Mr. Heater Natural Gas Garage Heater -...

1 Answer

Raypak spa heater pr5 service code message


check pressure switch if no voltage both sides of switch bad switch or plugged copper line or loose wires

Oct 02, 2012 | Raypak Rp2100 Pool & Spa Heater Lonox 407k...

1 Answer

How do you replace a pool heater pressure sensor?


check pressure switch to see if voltage both sides if not see if copper tube is plugged make sure filters are clean

Sep 22, 2012 | Jandy Laars LX Pool Heater / 400,000 BTU /...

1 Answer

What is causing my P-R405AL to not ignite? It shows SPK, CFH and the 'flame' flashes, but no ignition or heat.


check gas pressure see if gas valve on if voltage to gas valve bad valve see if cobwebs in lines or flame sensor if only runs a few seconds if new check wiring

Jan 17, 2012 | Raypak Rp2100 Pool & Spa Heater Lonox 407k...

1 Answer

Raypak 2100 just get SPK then LO codes. won't ignite


if wired 120 volt check wiring and check gas pressure see if lines have cobwebs

Jan 02, 2012 | Raypak Rp2100 Pool & Spa Heater Lonox 407k...

1 Answer

IT TURNS ON THEN SHUTS OFF,DISPLAY FLASHES SERVICE AGS


Per your owner's manual:


AGS

(automatic gas shut-down)


1. Oscillating pump pressure.

1. Clean filter or identify and repair cause of pump oscillation.

2. Low gas supply pressure.

2. Identify and repair incorrect supply pipe size or pipe line blockage.


Refer to qualified service personnel.

3. No flame at burners.

3. No flame at burners. 3. Identify and correct loose wiring connections, or problems with igniter, flame sensor, gas valve, or ignition control.


Refer to qualified service personnel.


For more info the manual is here:
http://www.jandy-downloads.com/pdfs/LXandLT_H02140B.pdf

John

May 29, 2011 | Jandy Laars LX Pool Heater / 400,000 BTU /...

1 Answer

I have the MHU45NG. About 2-3 years old. Will not ignite. Board is flashing green coorectly. After the 3rd try it kicks off like manual says. Gas supply and thermostat are good. Hoping for...


check the flame sencor is clean heater might need a clean try blowing it out with air line check limit is not shutting off to soon , try jumping out thermostat ,

Dec 10, 2010 | Mr. Heater Natural Gas Garage Heater -...

2 Answers

As soon as i hook up the thermostate it flashes the 3 flashes code and i have already tryed a new thermostate .... as soon as i unhook the thermostate it flashes for normal operation with no call for heat...


Try using it without the thermostat, tie the two thermostat wires together or put a jumper between
r and w. If furnace operates, you must have wrong style of thermostat

Jan 28, 2010 | Mr. Heater Natural Gas Garage Heater -...

1 Answer

Turn on green light flashes


Count the flashes before a pause. A steady on is bad ground or loose igniter. 2 flashes is either low gas pressure, bad flame sensor, gas valve wires loose or bad ignitor. 3 flashes is a bad pressure switch, or blocked vent. 4 flashes is a bad roll-out switch or open contact. 5 flashes is bad wiring to gas valve or flame sensor, 6 flashes is either a bad control board or bad thermostat.

Oct 13, 2009 | Sterling RF75 Natural Gas Heater (75,000...

Not finding what you are looking for?
Mr. Heater MHU45NG Logo

154 people viewed this question

Ask a Question

Usually answered in minutes!

Top Mr. Heater Heating & Cooling Experts

paulcarew

Level 3 Expert

2458 Answers

Dan Webster
Dan Webster

Level 3 Expert

8220 Answers

Mack Baxter

Level 3 Expert

381 Answers

Are you a Mr. Heater Heating and Cooling Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...