Micro Minnie 2108DS water heater problem

[IdahoHunter]

I’m away from home visiting family, and we are staying in our trailer at a campground with full services. First time that we aren’t boondocking. The hot water tank isn’t providing hot water regardless of whether I have the electric or gas heater switch turned on. It doesn’t even ignite the gas, but the propane is on (furnace, fridge, and cooktop works).

I’m hoping you guys can point me to a fuse or something else to check because I don’t have time to dive into troubleshooting this like I’d normally do. I don’t want to take away from family time with kids and grandkids.

The system worked fine a few weeks ago in the mountains, and to me, the fact that it won’t even ignite the propane suggests something is preventing the water heater from working in any mode. Could be something simple as I’m not as experienced working on the hot water heater.

Any help would be greatly appreciated!

Thanks, Mike

 

[Morich]

We don't get the best info on the trailer group, so if you can take a look and find the brand and model of heater, we can likely find a manual to guide repair.
But if you have a meter on hand, taking a look at a couple points on the water heater may be a good place to start if going by shotgun method.
Taking a look at the back side, there are likely to be some points for 12Volt and 110 AC to connect. checking for both them may be quick enough to take a look on the odd chance it is an electrical problem keeping it from firing up???
I feel like you might be able to spot where each of those come in and making sure they are both getting to the heater might be step one? The 12VDC may be one that would stop any of the three modes from working as it likely does the controls.
No 12VDC may mean all the rest are dead? If we go with that shotgun idea, it might be as simple as a 12V fuse blown?

 

[IdahoHunter]

We don't get the best info on the trailer group, so if you can take a look and find the brand and model of heater, we can likely find a manual to guide repair.
But if you have a meter on hand, taking a look at a couple points on the water heater may be a good place to start if going by shotgun method.
Taking a look at the back side, there are likely to be some points for 12Volt and 110 AC to connect. checking for both them may be quick enough to take a look on the odd chance it is an electrical problem keeping it from firing up???
I feel like you might be able to spot where each of those come in and making sure they are both getting to the heater might be step one? The 12VDC may be one that would stop any of the three modes from working as it likely does the controls.
No 12VDC may mean all the rest are dead? If we go with that shotgun idea, it might be as simple as a 12V fuse blown?

I can certainly do some investigating when we get back to the campsite. I have the manual for it in the trailer, but was taking a stab at someone on here seeing this problem before. I don’t even know where it’s fused at just yet. I didn’t see a fuse labeled for the hot water on the converter’s fuse panel.

 

[Morich]

Yes, understand not having the good info. You may be able to tell where the 12 and 110 get to the thing , just by looking at wires. They will be different than the ones they add as they built the heater and you may be able to see some things like wires that come in through the heater side or maybe go to a point that has some form of label?
Hard to deal with on the trailers where we don't get the better info but the 12VDC would seem to be a good one to look at as they often use that as a control , not just to use when you set it 110 or propane.
Just thinking of how or what would make the different ways of heating go out at the same time?

 

[Wmlunt-WO]

I would check the t’stat first. If it has failed it will never ‘call for heat’ common to all. Guess it has failed open.
Else no 12v for controls, maybe blown fuse?
Bill

 

[eatSleepWoof]

I had this problem in the summer of 2024 on my 2022 2108FBS. It was the thermal fuse that had blown.

You can temporarily bypass it (it's just installed inline and you can remove it with your hands, re-connect the bit of wiring that's left once the fuse is removed) to test whether the fuse is the problem. You can even use the water heater without the fuse, just be aware of elevated risks.

My trailer is winterized so I don't have a way to take a photo of it, but the fuse is located on the water heater, under the exterior access panel. It'll be on the thermostat line and is easy to find. A pair of pliers may be handy for pulling it off, as space is limited and you'll need good grip on the plug.

I used these replacements to replace mine, and carry them in the trailer now. No issues since replacing.

 

[IdahoHunter]

I had this problem in the summer of 2024 on my 2022 2108FBS. It was the thermal fuse that had blown.

You can temporarily bypass it (it's just installed inline and you can remove it with your hands, re-connect the bit of wiring that's left once the fuse is removed) to test whether the fuse is the problem. You can even use the water heater without the fuse, just be aware of elevated risks.

My trailer is winterized so I don't have a way to take a photo of it, but the fuse is located on the water heater, under the exterior access panel. It'll be on the thermostat line and is easy to find. A pair of pliers may be handy for pulling it off, as space is limited and you'll need good grip on the plug.

I used these replacements to replace mine, and carry them in the trailer now. No issues since replacing.

Bingo!!! Thank you so much! We just got back to the trailer, and I removed the thermal fuse. Then I connected the remaining wire with spade connection, and the heater fired right up on propane. I did a continuity test on the thermal fuse out of curiosity, but I'll need to look up what they should read since I see an internal component in line with the wire.

Thank you so much again! This is what I was hoping to glean from someone on here so I wouldn't need to take precious time away from visiting with family.

In the time it took me to fire up my laptop and write this, we have hot water again. For safety's sake, I don't think I'll leave the electric or gas function of the heater running overnight. I'll order the correct replacement parts + spares.

Mike

 

[bcborn]

Looking at our Mar 2023 water heater externally, the fuse kit linked from eatSleepWoof's reply looks to be in place.

Would this suggest the prior owner would have had the no heat issue and the replacement was performed?

 

[Wmlunt-WO]

Does it test for continuity? Or is it blown?

 

[IdahoHunter]

I read the part numbers off the component that was on my heater, and I found a set of 4 replacements. I don’t know if matching a pn replacement is critical, but it can’t hurt. This is what I ordered for my Dometic heater:

Amazon.com

 

[IdahoHunter]

Does it test for continuity? Or is it blown?

No continuity tested both directions.

 

[Wmlunt-WO]

Continuity is bi directional, not a diode.
Glad you have it repaired. I would check the owners manual when you have a chance, likely 4 different heat/current ranges, good to have the proper one to trip when warranted.
Bill

 

[bcborn]

All good now?

 

[Wmlunt-WO]

I sure hope so… that is not a thermal fuse, but over current fuse, likely a short to ground would pull high current. If not plugged in to shore power the trailer ground is floating, yikes!
Bill

 

[IdahoHunter]

All good now?

Yup. The four pack thermal cutoff kit arrived from Amazon, and I installed the replacement thermal fuse. Working fine, and I put the remaining three thermal fuses in my spare parts bin that I have in the passthrough.

 

[bcborn]

Is the picture I posted earlier OEM and you just replaced the thermal fuse as shown in my picture.

Some of the online pictures I looked at, it seemed this type of thermal fuse replaces the thermal disc type, which requires some of the other parts

Please clarify for all

 

[IdahoHunter]

Is the picture I posted earlier OEM and you just replaced the thermal fuse as shown in my picture.

Some of the online pictures I looked at, it seemed this type of thermal fuse replaces the thermal disc type, which requires some of the other parts

Please clarify for all

I'm guessing yours was replaced because the right angle in the thermal fuse is different than my OE fuse, which was straight (pic below). I only replaced the thermal fuse. It's shown in the 2nd pic with the one end loose before I plugged it into the heater.

 

[Morich]

I think there is some confusion about this thermal fuse and what may make it open.
It is not a fuse for limiting current but for sensing thermal/ temperature at the heater.
The location and name are both clues that it opens when the heater gets too high and location is just above where the heat would be highest if flame rolls out of the combustion chamber!
It might be noted that when you get it to final location it is almost directly above the end of the combustion chamber!
It's made to melt and shut off both electrical and propane heating ie thermal!

 

[bcborn]

Morich, are you suggesting one of the two multi terminal sensors (Eco/T'Stat) behind the foam may also be part to blame for this component ultimately failing.

 

[IdahoHunter]

I think there is some confusion about this thermal fuse and what may make it open.
It is not a fuse for limiting current but for sensing thermal/ temperature at the heater.
The location and name are both clues that it opens when the heater gets too high and location is just above where the heat would be highest if flame rolls out of the combustion chamber!
It might be noted that when you get it to final location it is almost directly above the end of the combustion chamber!
It's made to melt and shut off both electrical and propane heating ie thermal!

That’s exactly what I learned when I looked into the function and parameters of this part when it took my water heater OOC. Most of the replacement thermal fuses I found said they open at 208°F.

I don’t know why mine opened. It seems to work fine, and it’s not very old. Shoot, half the time when I go into the mountains it’s empty from winterizing. But, it will get a lot more use in good weather now that my wife is retired. Hopefully it’s an anomaly.