Refrigerator Won't Cool Below 40 Degrees

[HarryB1]

A couple of weeks ago my neighbor purchased an older RV with a Dometic RM1350 refrigerator that holds the refrigerator temperature at 40 degrees as verified by a number of different thermometers. I'm wondering if one of the control boards is defective.

The refrigerator is located in a slide, and the air flow channel is well constructed (although it could be slightly improved at the top). The heaters' resistance is within spec, although the wattage they draw is on the low side of spec. And the thermistor's resistance is also within spec when tested in a cup of ice cold water.

The fins occasionally develop some ice, but they are typically wet.

However, the eyebrow display shows 32 degrees when the actual temperature is 40 degrees. And when the thermistor is placed in a cup of ice cold water, the eyebrow display shows 25 degrees.

Even though the interior temperature is 40 degrees, the heaters are cycling on and off. Is there anything we're missing?

[Old-Biscuit]

1st off........
Display is actual temp of food compartment...not set temp
2nd....
Unplugging the thermistor in THAT model will not cause continuous cooling..it will shut fridge down until thermistor is plugged back in or faulty one replaced
3rd...
Moving thermistor location will NOT have much if any affect on temps because fridge has an 'adjustable thermostat' ----1-5 settings



OP
Are the fans in outside compartment functioning...running/moving air?
How are you measuring temp in food compartment?

Fridge has an 'automatic cooling unit cycling system'
Shuts down heating cycle every 48 hours to 'defrost' fins in food compartment

Air Leaks
Door seals......if not fully sealing air leaks in causing warmer then normal temps
Drip tray drain hose 'check valve' if missing in end of drain hose or if drain hose is cracked.air leaks in causing warmer then normal temps


Upper display panel testing continuity
There are 4 contacts on end of circuit board
Temp set point....continuity between 1 & 4
Auto/Gas..........continuity between 3 & 4
On/Off............continuity between 2 & 4
(see pg. 21 in Service Manual Link)

Service Manual RM1350

[dougrainer]

1. Control Boards NEVER cause cooling performance problems
2. As another poster stated, a 4 door refer in a slide room requires that a extra upper 12 volt fan be installed to force the hot air out the top door.
3. ALL your parameters you tested are to spec. The only thing you have NOT stated is HOW you test the interior temp. The ONLY valid way is a glass of water after 24 hours
4. The FIN temp will be 10 degrees colder than the interior temp----26 degree fins 36 degree interior temp
5. Moving the Thermister does NOTHING for a adjustable refer tstat.
6. 120 volt voltage can make a difference on performance. BELOW 115 volts will impact Heat element performance. ALWAYS use LP for 24 hours to verify performance of the refer if Line voltage is low or suspect. Doug

[Halmfamily]

I installed 4 muffin fans on a thermostat in the top vent that would turn on around 100° and that did did help.

[CarnationSailor]

According to the mobile tech that improved the performance of our slide-mounted refer, airflow in a slide-mounted refer is quite often the problem. Our installation allowed the hot air to circulate around the "box" instead of going from the lower vents, past the heat exchanger, and out the top vents. He installed card board baffles that kept the hot air away from the top and sides of the "box". Made a big improvement.

[Ivylog]

Unplug the thermistor...should go into continuous cooling...no cycling. If this gets your temps cold enough then find a location for the thermistor (near the fins, not on) that gets you the temp you want with it plugged in.

[donn0128]

Adjust the temp sensor bulb located on the far right fin inside the refer near the top. There are instructions all over the place about how to move it. BTW, the display shows set temp not actual temp.