Maintenance & Restoration

Bob Miller · 09-05-2012, 03:51 PM

I have a Dometic RM-23a that is original to my 1973 Hunter Compact-II, In condition, it almost looks like it just came out of the box.
Here's the problem: It works fine on 120VAC, goes right down to freezing. However, it does not like keeping the LP flame on, even for a few seconds.

I have taken everything apart and checked out everything with the Dometic troubleshooting manual and everything works fine. If I put the burner in, without it's outside shroud, it lights off and the flame safety locks in just fine. It will stay lit for hours like that.

As soon as I put the metal box around the burner all it will do is POP when lighting is attempted. The flue is clear, albeit a bit rusty inside. I'm almost thinking that there is a manufacturing or an installation problem and that it was just never used on gas.

I am tempted to drill a few more vent holes in the side of the burner chamber to let more air in. Any thoughts??

Many Thanks.

Thomas G. · 09-05-2012, 03:59 PM

I don't know the answer, but tiny spiders are probably involved.

Mine drove me crazy until I took an air compressor and blow gun to every orifice.

Raz · 09-05-2012, 04:09 PM

Well there's a puzzle. Perhaps the shroud is interfering with the thermocouple or the ignitor. I would look for frayed wires where each passes through the shroud. Then I would carefully pull out the thermocouple and test it with a propane torch. With the thermocouple hot and the shroud in place, does it light? Also bypass the ignitor. Can you light it with an aim-n-flame? Best I can think of for now. Raz

Darwin Maring · 09-05-2012, 05:11 PM

Tom and The Raz have provided Most Excellent answers. I would try their suggestions B 4 drilling anything.

Bob Miller · 09-05-2012, 06:39 PM

As I mentioned, this is a very old and somewhat simpler system. There are no wires except for the 120VAC heating element and a temp control. And nothing passes through the shroud except the non-electric flame sensor and the jet, and it's in a fitting. As far as an igniter, it uses a gear wheel and flint system, somewhat like a Zippo lighter. If just seems to act like it uses up all of it's oxygen when it fires and 2-3 minutes again will again try to fire. I can see all the way through the flue pipe and it's clear. I'll try blowing out everything tomorrow.
Thanks for all the help.

Raz · 09-05-2012, 06:58 PM

Quote:

Originally Posted by Bob Miller

As I mentioned, this is a very old and somewhat simpler system. There are no wires except for the 120VAC heating element and a temp control. And nothing passes through the shroud except the non-electric flame sensor and the jet, and it's in a fitting. As far as an igniter, it uses a gear wheel and flint system, somewhat like a Zippo lighter. If just seems to act like it uses up all of it's oxygen when it fires and 2-3 minutes again will again try to fire. I can see all the way through the flue pipe and it's clear. I'll try blowing out everything tomorrow.
Thanks for all the help.

Are you sure the flame sensor is not electric, i.e. a thermocouple? The typical system would have a thermocouple powering a gas valve. It might look like a small copper tube. A thermocouple failure matches the symptoms. Best guess. Hope you figure it out. Raz

Darwin Maring · 09-05-2012, 08:54 PM

It has to have a thermocouple. The copper or brass (Fatter on the end tube) sets in the flame and the skinny part of the tube goes to the gas controller. The heat from the pilot lite warms up the thermocouple and that activates the gas regulator to turn on the big portion of the flame. Now all this means you will have a thermostat in the system too.

Some thermocouples produce a minute amount of electricity to the regulator and others simply move a mechanical thing in the regulator (No electricity) on the later.

The reason for gas devices having thermocouples is to shut off the gas flow should the pilot lite go out. This is a safety device to keep you from blowing up your camper.

By the way: Gas fridges on campers are a major cause of camper fires. One other danger is that their pilot light could ignite the gas fumes from you filling up your tow vehicle gas tank should you let the fridge run on propane gas during travel.

Bob Miller · 09-06-2012, 11:10 AM

Progress
I blew out all the dust and dirt below the burner housing and now it burns fine.....
NEXT Problem:
My spark lighter has now sparked it's last. Has anyone replaced the flint in the spark lighters on these refrigerators. If so, is it a standard cigarette lighter flint or is it a Domentic specific part?
Thanks again for the help

David Tilston · 09-06-2012, 11:15 AM

I think it is a pizo spark igniter. Dometic specific part. You could just use a lighter.

Bob Miller · 09-06-2012, 11:39 AM

This is a 1973 Dometic and it's really a spark wheel lighter with a small piece of flint, not to unlike a Zippo lighter. .
There is a little knob inside the refrigerator that you turn while holding the gas valve ON. Unfortunately the entire burner chamber is enclosed with two layers of metal and there is no easy route to stick a BBQ lighter in there. It worked when I started the project, but the little bit of flint that was left crumbled.