Dometic RM46E 3-way RV Refrigerator Over Cooling

[bentSpaceTime]

My friend has a Dometic RM46E 3 way refrigerator in her trailer that over cools. It’s probably from the 70’s.

I cleaned the valve and valve seat per the manual, as it says:

“Dirt on the thermostat gas valve or seat prevents the thermostat valve from completely closing, consequently it lets through some gas when in closed position.?This condition may prevent reducing the flame to the required minimum. It will cause too low cabinet temperature. “

The cleaning didn’t seem to solve the problem though…

I tested the thermostat per the manual and it seems to be working.

“If the thermostat control assembly loses its charge, it will become inactive. To test for a lost charge, while the flame is reduced to minimum and the temperature control is set at a numbered position on its dial: Remove thermostat capillary tube from its clamp in the evaporator and warm capillary end with the hand, If the flame fails to increase in size, the thermostat has lost its charge and the thermostat must be replaced.”

There is definitely a difference between the low flame and the higher on flame.

I also tried moving the thermostat capillary tubes in the box up and down to no avail.

Last weekend as we were camping I tried playing with the gas/electric knob/valve which shuts off the gas. I turned it part way towards electric, which restricts the flow of gas a little, to were the flame became a little smaller and then the fridge seemed to operate perfectly staying between 34-38 degrees. The thermostat knob was set on 1. However by the time we got home the flame on the fridge was off and I’ve been playing with it again to try and find that balance point.

Any ideas what might be the actually problem here?

My guess is the bypass flame is too big causing it to cool when it shouldn’t be.

[Chris_Bryant]

bentSpaceTime wrote:

Chris Bryant wrote:
Thanks Doug- darned autocorrect!

The easiest thing to check is, with the refrigerator down to temperature (cold), does the gas thermostat modulate the flame in the middle of the travel, or just right at the very bottom? If it only makes the flame smaller right at the bottom, it's bad. If it is in the middle of the range, we can work with it.

What do you mean by travel?

The range between full counter clockwise ( warmest), and full clockwise (coldest).
The thermostat will modulate the flame to low at full counter clockwise, even if it has lost its charge, but we want to see if it will modulate at "working" setting, right in the middle of its range.

[bentSpaceTime]

Chris Bryant wrote:
Thanks Doug- darned autocorrect!

The easiest thing to check is, with the refrigerator down to temperature (cold), does the gas thermostat modulate the flame in the middle of the travel, or just right at the very bottom? If it only makes the flame smaller right at the bottom, it's bad. If it is in the middle of the range, we can work with it.

What do you mean by travel?

[Chris_Bryant]

Thanks Doug- darned autocorrect!

The easiest thing to check is, with the refrigerator down to temperature (cold), does the gas thermostat modulate the flame in the middle of the travel, or just right at the very bottom? If it only makes the flame smaller right at the bottom, it's bad. If it is in the middle of the range, we can work with it.

[dougrainer]

bentSpaceTime wrote:

Chris Bryant wrote:
Because the thermostat is modulating the flame, I doubt it has lost its charge, unless it only modulates at the very bottom of its range.
Have you checked the lip pressure? I would sure start with that.
I'm pretty sure I have several of those v35 thermostats, if I can find them.

How do you check the lip pressure?

You connect a Manometer and when it goes to bypass causing the LP pressure to drop. That is how a bypass LP tstat works. Doug

[dougrainer]

bentSpaceTime wrote:
Does moving the capillary tubes up and down on the fresh food evaporator fins do anything, as far as adjusting the temperature in the cabinet?

No. Those metal tubes get VERY brittle over time and you have to be extremely careful when moving them. It does not take much to crack one and then the tstat is useless. Doug

[bentSpaceTime]

Does moving the capillary tubes up and down on the fresh food evaporator fins do anything, as far as adjusting the temperature in the cabinet?

[bentSpaceTime]

I was trying to check the operation on 120 volts, but the knob that switches from gas to electric is missing. It's the kind where you turn it the the right for electric and then push it in and turn it further. Any idea if 120 is all the way turned to the right vs. 12 volts?

[bentSpaceTime]

Chris Bryant wrote:
Because the thermostat is modulating the flame, I doubt it has lost its charge, unless it only modulates at the very bottom of its range.
Have you checked the lip pressure? I would sure start with that.
I'm pretty sure I have several of those v35 thermostats, if I can find them.

How do you check the lip pressure?

[Chris_Bryant]

Because the thermostat is modulating the flame, I doubt it has lost its charge, unless it only modulates at the very bottom of its range.
Have you checked the lip pressure? I would sure start with that.
I'm pretty sure I have several of those v35 thermostats, if I can find them.

[bentSpaceTime]

dougrainer wrote:


Yes, I found a few listings for the Gas Tstat. NONE for the electric tstat. So, if the Gas is defective, maybe one of the suppliers still has the gas tstat (pn 62303). Doug

Awesome! Thank you! Where did you see it listed?

[dougrainer]

bentSpaceTime wrote:
Would replacing the thermostat fix the problem, if the bypass flame is too big?

Yes, I found a few listings for the Gas Tstat. NONE for the electric tstat. So, if the Gas is defective, maybe one of the suppliers still has the gas tstat (pn 62303). Doug

[bentSpaceTime]

Going to test it on 120 and see what happens.

[bentSpaceTime]

It looks like it does have two thermostats, one for the gas and one for the 120 electric. Each has its own capillary tube.

[bentSpaceTime]

Would replacing the thermostat fix the problem, if the bypass flame is too big?