Mr. Heater Gas Valve Problem

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SpeedThrills

SpeedThrills

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I have a Model No. MH25NG Item No. F272200 Mr. Heater in my garage. https://www.amazon.com/dp/B00006L7UZ/?tag=fabo03-20
I installed it about 10 or 12 years ago, and it's been fine until the last coule of years. The gas valve needs a tap on the side for it to operate.

This link says it's discontinued. VS820A1039 by HONEYWELL - Buy or Repair at Radwell - Radwell.com Searching shows other valves that will possibly interchange? Some cost more than a new heater. ($300 ish)

Can a gas valve be repaired? Is it sticking or? I've never worked on one.

I'm a capable mechanic. I just don't want to blow up my garage. :rolleyes:
 
I would see if there are any qualified repair shops that can rebuild the valve. Personally, I wouldn't want to chance rebuilding it on my own. There is too much at stake.
 
No help here but curious what you do. I have a Mr Heater 45K btu NG. I bought the LP conversion kit at the time. I wonder if a conversion kit for yours would "fix" it? Of course you then run off propane .
 
YOU CAN NOT repair combination gas valves. It is not "code" there are no parts available, and there is no repair information. PERIOD.

Found this

Honeywell VS820A1088 Millivolt Combination Gas Valve

OP what is wrong with the heater/ valve? That is what is known as a "millivolt" or "self powered system

SOME STUFF!!!



HOW THEY WORK A thermopile gas valve does several functions all in one big box
1...There is a pilot tap-off and on most newer valves, the pilot is shut off "safe" in the even of a flame failure which allows the thermopile to cool. In any evet cooling of the thermopile due to loss of flame requires 100% shut off of AT LEAST the main gas supply.......with NO leak

2...The pilot may or may not be a modern "oxygen depletion setup." Regardless the pilot MUST be kept clean or it will not generate enough heat to reliably keep the thermopile engaged. Remove pilot assy and tubing pull it all apart and blow it out with air. "Look" through the pilot orifice and visually confirm it is open before and after you blow it clean. Do not try and clean it with wire--it is too small

3....The thermopile really does 2 jobs---it's heat and generated power holds the safety open so that the valve can operate. In the event of loss of flame the cooling and loss of power at the thermopile causes the valve to close. In addition, the power output opens the main burner valve during normal operation..

4....Thermostat voltage drop (dirty contacts and type of stat, etc) as well as SIZE AND LENGTH of stat wire cause these to be "fussy" "on the edge" or undependable. ALWAYS bypass the stat (if used) right at the valve to see if this is a problem

Also, some appliances have additional series wired "safeties" in the millivolt chain. ANY thermo-switch/ safety in series adds the probability of voltage drop in these "on the edge" systems. Follow the circuit diagram and find out.

5....Thermopile output regardless of internet wisdom is difficult to test. If you have bypassed the control wiring to test, cleaned the pilot, and the thing still will not operate, always replace the thermopile, and make certain it is properly IN the pilot flame

Thermopiles FAIL and are always "on the ragged edge."

You do NOT absolutely have to replace that valve with the same part number. So long as the valve can handle the BTU range of the heater (IE it is not too small for the gas flow), so long as it is a millivolt/ thermopile type valve, and will physically fit in the space in the burner, you can sub other brand valves.

ALSO. If there is no other appliances on the piping to that unit CONFIRM that you have adequate gas pressure TO the appliance. This requires a low pressure measurement such as a U-tube manometer or the electronic equivalent. Pressures are different for nat vs LP gas EG it might be that somehow water has gotten into the system. THIS WOULD BE RARE but has happened. Water might be "in a low spot" in the piping. Gas piping occasionally DOES become plugged, sometimes with foreign material that had ALWAYS been in the pipe, and finally just migrated enough to restrict flow. This problem however is usually indicated by a good pilot....good ignition of main burner........followed by "petering out" of the flame as flow drops off

I spent about a dozen years in the 80's --early 90's servicing HVAC / R
 
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There's a lot of similar problems being reported about those Mr. Heater valves. The Garage Journal has several threads too.
 
I found this is this correct instructions?

http://www.allpartsinc.com/media/attachments/products/18672REVD.pdf

You want to be absolutely sure the wall stat is rated for "millivolt" systems. I have a living room corner heater. When it was installed I used no14 "Romex" as a stat wire because I wanted NO problems with voltage drop.

Don't get me wrong. Before the advent of 12V electronic ignition (in RVs) there were SKILLIONS of millivolt/ self powered systems in use. MANY MANY small houses and apartments that did not have central heat had some form of self powered gas heater Ever seen the tall "wall" heaters? or the more modern wall mount boxy heaters? Or the "corner fireplace" ones? ALL these are self powered systems
 
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I don't know if it will help, but check out Mr. Slim by Mitsubishi. They may have the valves in common with one another. Just a thought for you.
 
67Dart273 said:
YOU CAN NOT repair combination gas valves. It is not "code" there are no parts available, and there is no repair information. PERIOD.

Found this

Honeywell VS820A1088 Millivolt Combination Gas Valve

OP what is wrong with the heater/ valve? That is what is known as a "millivolt" or "self powered system

SOME STUFF!!!



HOW THEY WORK A thermopile gas valve does several functions all in one big box
1...There is a pilot tap-off and on most newer valves, the pilot is shut off "safe" in the even of a flame failure which allows the thermopile to cool. In any evet cooling of the thermopile due to loss of flame requires 100% shut off of AT LEAST the main gas supply.......with NO leak

2...The pilot may or may not be a modern "oxygen depletion setup." Regardless the pilot MUST be kept clean or it will not generate enough heat to reliably keep the thermopile engaged. Remove pilot assy and tubing pull it all apart and blow it out with air. "Look" through the pilot orifice and visually confirm it is open before and after you blow it clean. Do not try and clean it with wire--it is too small

3....The thermopile really does 2 jobs---it's heat and generated power holds the safety open so that the valve can operate. In the event of loss of flame the cooling and loss of power at the thermopile causes the valve to close. In addition, the power output opens the main burner valve during normal operation..

4....Thermostat voltage drop (dirty contacts and type of stat, etc) as well as SIZE AND LENGTH of stat wire cause these to be "fussy" "on the edge" or undependable. ALWAYS bypass the stat (if used) right at the valve to see if this is a problem

Also, some appliances have additional series wired "safeties" in the millivolt chain. ANY thermo-switch/ safety in series adds the probability of voltage drop in these "on the edge" systems. Follow the circuit diagram and find out.

5....Thermopile output regardless of internet wisdom is difficult to test. If you have bypassed the control wiring to test, cleaned the pilot, and the thing still will not operate, always replace the thermopile, and make certain it is properly IN the pilot flame

Thermopiles FAIL and are always "on the ragged edge."

You do NOT absolutely have to replace that valve with the same part number. So long as the valve can handle the BTU range of the heater (IE it is not too small for the gas flow), so long as it is a millivolt/ thermopile type valve, and will physically fit in the space in the burner, you can sub other brand valves.

ALSO. If there is no other appliances on the piping to that unit CONFIRM that you have adequate gas pressure TO the appliance. This requires a low pressure measurement such as a U-tube manometer or the electronic equivalent. Pressures are different for nat vs LP gas EG it might be that somehow water has gotten into the system. THIS WOULD BE RARE but has happened. Water might be "in a low spot" in the piping. Gas piping occasionally DOES become plugged, sometimes with foreign material that had ALWAYS been in the pipe, and finally just migrated enough to restrict flow. This problem however is usually indicated by a good pilot....good ignition of main burner........followed by "petering out" of the flame as flow drops off

I spent about a dozen years in the 80's --early 90's servicing HVAC / R
Click to expand...
Thanks. I can understnd why they're not serviceable.
The problem is it needs a "tap" to get it to open. The heater works fine until the next time it needs to start, same problem, a tap gets it going.

CudaChick1968 said:
There's a lot of similar problems being reported about those Mr. Heater valves. The Garage Journal has several threads too.
Click to expand...
Thanks. Yes, I posted over there, too. Got a link to a cross reference chart that I'll post down further.

67Dart273 said:
I found this is this correct instructions?

http://www.allpartsinc.com/media/attachments/products/18672REVD.pdf

You want to be absolutely sure the wall stat is rated for "millivolt" systems. I have a living room corner heater. When it was installed I used no14 "Romex" as a stat wire because I wanted NO problems with voltage drop.

Don't get me wrong. Before the advent of 12V electronic ignition (in RVs) there were SKILLIONS of millivolt/ self powered systems in use. MANY MANY small houses and apartments that did not have central heat had some form of self powered gas heater Ever seen the tall "wall" heaters? or the more modern wall mount boxy heaters? Or the "corner fireplace" ones? ALL these are self powered systems
Click to expand...
They are the same instructions I have. I also have the instructions for the thermostat and control valve, too. All was included with the heater.
This is a link I got from someone on Garage Journal: https://controlscentral.com/Portals/0/HW Gas Valve Cross Reference.pdf If I understand it, I need a VS820A1088. If so, it's about $300, and so is a new heater.
I'll check connections. I used 14 ga stranded for the stat. Probably about 20'. Thanks for the detailed reply. I appreciate it tremendously.
 
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"A tap" might indicate just what I was getting at....that something is "on the edge." Might be the pilot is dirty and does not get the thermopile hot enough, and it doesn't output enough power, or that the thermopile is getting old and same thing, OR that the stat wire run is too small or too long, or that the stat contacts are getting dirty

So bypass the stat right at the unit and see if it works. If it does you are on the right track. Clean the pilot see if the flame looks good. IT SHOULD NOT BLOW which indicates a partially clogged pilot orifice. It should be soft and quiet, and might have "some yellow" showing at the tip. If that is the case try replacing the thermopile.

I may have worded poorly.

When you light the pilot and hold down the spring knob, you are manually opening the electrical solenoid valve safety. This is what allows gas to flow an "enables" the valve to operate, when the pilot flame blows out, this loses power and goes shut. In normal operation the thermopile heats up via the pilot, it outputs electrical power and holds that open. But on these "self powered" units, part of the t-pile power also has to open the main gas valve--when the stat calls for heat, so it is an extremely low power delicate device. Any of the causes I mentioned above can stop it operating.
 
67dart273 listed about all that can be done but a simple corroded terminal or connector plug or bad ground can cause it to need a tap. Then it gets the contact it needs. Easy to check that.
 
The pilot looks the same as it has the whole time I've owned it.

I checked connections, and bypassed the thermostat. With the stat bypassed, it still needs a tap to ignite. Maybe a new thermocouple is worth a shot? The exact part is $37 to $45. I saw one for $28. I don't believe that one. I also see several others (not the Mr. Heater 09360 exact replacement) between $10 and $15. Is a thermocouple a generic item?
 
It's actually a thermopile. A thermocouple is smaller and puts out less power. Thermocouples are used typically on water tanks and older pilot type furnaces with 24V valves. a thermopile is normally "fatter" about 1/2" dia. and produces more power also known as 750 millivolt

I would CERTAINLY gamble on a thermopile before I spent the money on a gas valve. It is the more likely problem, and you may need one later, if not now. Regardless of the pilot "look" I'd pull it apart and blow it out. Use shop air, IE fairly high pressure, 50psi or more if you can get it, a rubber tipped blow gun.

Typical thermopile. They are called a pile because they contain a number of thermocouples

71auPDjg4jL._AC_SL1500_.jpg


Typical thermocouple, about 3/16 in dia. Not what you want here
81RQiiCjT8L._AC_SL1500_.jpg


Prices are all over the map just try and deal with someone you think you can trust
 
67Dart273 said:
It's actually a thermopile. A thermocouple is smaller and puts out less power. Thermocouples are used typically on water tanks and older pilot type furnaces with 24V valves. a thermopile is normally "fatter" about 1/2" dia. and produces more power also known as 750 millivolt

I would CERTAINLY gamble on a thermopile before I spent the money on a gas valve. It is the more likely problem, and you may need one later, if not now. Regardless of the pilot "look" I'd pull it apart and blow it out. Use shop air, IE fairly high pressure, 50psi or more if you can get it, a rubber tipped blow gun.

Typical thermopile. They are called a pile because they contain a number of thermocouples

View attachment 1715665148

Typical thermocouple, about 3/16 in dia. Not what you want here
View attachment 1715665153

Prices are all over the map just try and deal with someone you think you can trust
Click to expand...
Okay. I'll look into a thermopile. (I've driven some real piles, never knew I was trusting one to heat my garage. ha ha)
I did read about the differences, I only called it a couple because the parts list I have calls it a thermocouple.
Is it generic, or should I stick with the correct replacement? I read this on GJ:

"And, finally, since both a thermocouple and a thermopile simply create a voltage difference between two wires when their ends are heated, different lengths of thermocouples will all generate the same voltage, just as thermopiles of different length. So you can use a longer thermocouple to replace a shorter one, and use a longer thermopile to replace a shorter one. They're like extension cords or garden hoses or battery booster cables in that respect. That's important to know when you're water heater's pilot light goes out and the hardware store doesn't have a thermopile of the right length. (Just buy a longer one.)"

And, I thought I was being lazy regarding checking the pilot. :rolleyes: I'll blow it out tomorrow. I have 115# of shop air.

Again, I appreciate your help. A new heater for $300 or so isn't that bad, but I like to learn and don't really want to scrap the old one if it's repairable.
 
They are generic unless the mounting is enough different that you just can't get it mounted and in that little heater there might not be much fiddle room. Without looking at it hard to say. I used to carry a couple different ones on the truck, and don't remember being "stuck" for lack of. But since you don't have any I'd be tempted to try to find an exact replacement. I don't think, overall, there are many different ones

The power / voltage is supposed to be the same. As long as they are a 750 mv thermopile, "in theory" they should work electrically
 
It has cycled several times and has worked every time!

On Wednesday, I checked connections and looked at the pilot. The connections seemed okay and the pilot "looked" as it has for years. (Falls under; "Don't Assume.")

The repair isn't as clear cut as I'd like it to be, but I'll cover what I did. Yesterday, I removed the thermocouple/pilot assembly to blow out the pilot.

-The flare nut holding the thermocouple in the bracket was loose. I don't think that mattered though. I don't think it's grounded through there. The entire heater is mounted to wood, no ground.

-One of the thermocouple wires was loose. I MOST LIKELY forgot to re-tighten it Wednesday when I was checking connections. (Old fartitus.) None of the connections were loose or dirty, so I don't think it mattered that I missed it.

-I think the problem was: Brown dust came out of the pilot orifice when I blew it out. That was probably limiting the gas flow, not allowing the flame to warm the TC enough to ignite.

So you can see it's not entirely clear cut. My complete lack of experience with heaters doesn't allow me to know for sure. Going by 67Dart273's guidance, I'm pretty sure it was the dirt in the pilot.

Thanks to all who responded, ESPECIALLY 67Dart273! I very much appreciate the help. Y'all saved me an expensive service call. (And they may have sold me a new valve!)
 
Your "fix" sounds exactly like what I've experienced. As I said earlier these systems operate "on the edge." A partially blocked orifice changes the flame characteristics and "I guess" the flame temperature. I've run into this many times. No, the nut mounting the thermopile does nothing, it only needs to be snug. All electrical is done through the 2 wire conductors.

You might examine the stat and see if it has open, exposed contacts. If so, put that in the back of your head, and maybe "next time" replace the stat as well. the stat on mine is "newer" electronic, and uses a small internal relay which I can hear when it cycles. It's been in the system since about 2010

The stat MUST be rated for millivolt systems. In the older days, a typical manual stat for 24V systems had what is called a "heat anticipator" which is essentially an adjustable rheostat in series with the contacts. Millivolt stats have no such
 
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