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 > Freezer works, fridge does not.

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Scovndrel

Washington

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Joined: 09/30/2019

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Posted: 09/30/19 12:17pm Link  |  Quote  |  Print  |  Notify Moderator

Hello!

I have a 2017 Travel Lite 625SL truck camper that I bought new.
The fridge/freezer unit which is a Dometic RM2354, mfg 2016, worked OK when I bought it, but never as well as the larger units in two other rigs I've owned. It got intermittent for a while, and now it is consistently bad.

I have a digital thermometer with an external probe that I jammed into the fridge through the thermistor hole, so I can check the temp without opening the door. It agrees within a few degrees with the analog one that is inside the fridge.

The problem is that while the freezer can freeze things and keep them frozen, the refrigerator portion does not get very cold, depending on the outside temp. For example, this morning we got a little frost on the roof of our house, and the RV fridge was at 35 degrees. On warmer days (65 to 75 degrees), the fridge gets to about 55 or 65 degrees, only a few degrees below the ambient air temp outside. But the ice packs in the freezer are still frozen solid. The cold just is not making its way into the fridge section well.

I am testing in my driveway. The fridge is perfectly level according to the bullseye level inside the fridge.

I have moved the thermistor clip to different areas on the fins, though my understanding is that this is a maximum of 5 degrees variance, not enough to cover what I am seeing.
The thermistor, when dunked in a glass of cold water with crushed ice, reads 9370 Ohms - right in "the zone". After reading a bit, I have now left the thermistor unplugged and we'll see what happens - it has been about an hour since I unplugged it.

There has never been an ammonia smell nor any yellow residue.

I have very little stuff in the fridge, so there is no air circulation blockage.

I have a little solar fan blowing on the condensor. It doesn't seem to make any difference. I have tried a battery powered fan inside the fridge. No difference.

It doesn't seem to matter whether it's on shore power or propane; in either case the chimney gets hot, the freezer stays frozen, and the fridge is tepid.

I have inspected the door seal. It is tight all the way around.

While I did not measure clearances exactly, I looked at the diagrams in the manual, and the fridge compartment looks pretty much the same as every RV fridge compartment I have looked at.

So, anyone have ideas what the heck is going on?
How, exactly, is the cold supposed to enter the main refrigerator compartment? Does it trickle down from the freezer, or is it a separate mechanism, attached to the cooling unit independently from the freezer?

the bear II

Torrance CA.

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Posted: 09/30/19 12:42pm Link  |  Quote  |  Print  |  Notify Moderator

If sun hits the side where the fridge is try shading that side to block the sun.

Our Dometic will heat up during the afternoon when the sun is hitting that side of the RV. When the sun goes down it gets back to 35 - 37 degrees.

bgum

South Louisiana

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Posted: 09/30/19 12:53pm Link  |  Quote  |  Print  |  Notify Moderator

The manuf. has gotten the tolerances so close that they don't cool. These refrigerators can work well for many years. The problem is that the manuf. has considered only making money. Go to a compressor retrofit.

ksg5000

Oregon

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Posted: 09/30/19 04:27pm Link  |  Quote  |  Print  |  Notify Moderator

Make sure the humidity switch located in the door jam isn't turned on - that provides power to heat tape which may eventually impact cooling capacity - also make sure your fridge light bulb is turning off when you close the door. Make sure there is adequate air flow behind the fridge. Also suggest you use YouTube and check burner orifice and baffle. If all that doesn't fix issue then it's possible you have partial blockage of the cooling unit - that usually is the beginning of the end but there are temp fix (google).


Kevin

Old-Biscuit

Verde Valley

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Posted: 09/30/19 04:38pm Link  |  Quote  |  Print  |  Notify Moderator

Insufficient cooling on both heat sources is one of three things
*Ventilation ----- draft/airflow is obstructed across backside of fridge (insultaion fallen down, top vent obsctructed/birds nests, etc)
*Thermistor ------ even when ohms are within range they still can be bad
(Unplug and run firdge for 12 hrs minimum then check temps)
*Cooling Unit ---- obstruction/blockage between freezer coil and food compartment coil. Freezer gets ALL of the cooling effect and food compartment is minimal.
(Unplug electric heat element leads from lower circuit board. Plug the leads DIRECTLY into the 120VAC Outlet and run fridge for 12 hrs minimum. This is 'forced' cooling....bypassing ALL controls. If cooling unit functions both compartments will get COLD. If cooling unit obstructed only freezer will continue to get cold.

Hopefully...bad thermistor.
Replace with a 'Snip-The-Tip'

Otherwise...cooling unit DEAD



AS for MOVING thermistor on FIN.
YOUR Model has Temp Settings (1-5)
Put the themistor BACK where it was (OEM Position--middle of fin)
Make sure the tip is just protruding above top of clip and it is secure against the Fin

Moving the thermistor UP/DOWN is for those Models that use an 'AUTO TEMP CONTROL' (no temp setting adjustments)
NOT your Model


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
On the Road Debt Free April '07
Off the road still Debt Free Jan. '14

Old-Biscuit

Verde Valley

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Posted: 09/30/19 04:42pm Link  |  Quote  |  Print  |  Notify Moderator

ksg5000 wrote:

Make sure the humidity switch located in the door jam isn't turned on - that provides power to heat tape which may eventually impact cooling capacity - also make sure your fridge light bulb is turning off when you close the door. Make sure there is adequate air flow behind the fridge. Also suggest you use YouTube and check burner orifice and baffle. If all that doesn't fix issue then it's possible you have partial blockage of the cooling unit - that usually is the beginning of the end but there are temp fix (google).


OPs Model does NOT have that feature.

wa8yxm

Wherever I happen to park

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Posted: 09/30/19 04:44pm Link  |  Quote  |  Print  |  Notify Moderator

On my Fridge (Also Dometic) I added two fans outside blowing up (4" computer fans they run all the time) and two more (Also 4") on the top shelf blowing towards the rear to circulate air.. ONE of them blows harder than the other and actually does a fair job of keepign the fins on the thermistor end frost free!!!

There is a kit you can get (about 100Bucks) includes both fans and lights mounts to the top of the fridge compartment.. CW among others sell it. I'm thinking of getting one because of the nuisance factor of what I use now.

Will decide tomorrow when I go shopping.

My Fridge currently is non-op awaiting repair next week. Thankfully I have a stand-alone ice maker, a second freezer and a coleman ice chest. Cooler.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377


Scovndrel

Washington

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Posted: 09/30/19 05:25pm Link  |  Quote  |  Print  |  Notify Moderator

Old-Biscuit wrote:

ksg5000 wrote:

Make sure the humidity switch located in the door jam isn't turned on - that provides power to heat tape which may eventually impact cooling capacity - also make sure your fridge light bulb is turning off when you close the door. Make sure there is adequate air flow behind the fridge. Also suggest you use YouTube and check burner orifice and baffle. If all that doesn't fix issue then it's possible you have partial blockage of the cooling unit - that usually is the beginning of the end but there are temp fix (google).


OPs Model does NOT have that feature.


Thank you for saving me the time I would have spent searching for that. Pretty sure I don't have a light bulb either. Will double check next time I go out there.

Scovndrel

Washington

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Posted: 09/30/19 05:27pm Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

On my Fridge (Also Dometic) I added two fans outside blowing up (4" computer fans they run all the time) and two more (Also 4") on the top shelf blowing towards the rear to circulate air.. ONE of them blows harder than the other and actually does a fair job of keepign the fins on the thermistor end frost free!!!

There is a kit you can get (about 100Bucks) includes both fans and lights mounts to the top of the fridge compartment.. CW among others sell it. I'm thinking of getting one because of the nuisance factor of what I use now.

Will decide tomorrow when I go shopping.

My Fridge currently is non-op awaiting repair next week. Thankfully I have a stand-alone ice maker, a second freezer and a coleman ice chest. Cooler.


Thank you for the ideas. I may hook up a fan on the fins on the inside connected to a little solar panel on the roof at some point, once basic functionality is restored, so I can pack more into the fridge. But I'll wait on that until I know whether I'm replacing it or not.

Scovndrel

Washington

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Joined: 09/30/2019

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Posted: 09/30/19 05:38pm Link  |  Quote  |  Print  |  Notify Moderator

Old-Biscuit wrote:

Insufficient cooling on both heat sources is one of three things
*Ventilation ----- draft/airflow is obstructed across backside of fridge (insultaion fallen down, top vent obsctructed/birds nests, etc)
*Thermistor ------ even when ohms are within range they still can be bad
(Unplug and run firdge for 12 hrs minimum then check temps)
*Cooling Unit ---- obstruction/blockage between freezer coil and food compartment coil. Freezer gets ALL of the cooling effect and food compartment is minimal.
(Unplug electric heat element leads from lower circuit board. Plug the leads DIRECTLY into the 120VAC Outlet and run fridge for 12 hrs minimum. This is 'forced' cooling....bypassing ALL controls. If cooling unit functions both compartments will get COLD. If cooling unit obstructed only freezer will continue to get cold.

Hopefully...bad thermistor.
Replace with a 'Snip-The-Tip'

Otherwise...cooling unit DEAD



AS for MOVING thermistor on FIN.
YOUR Model has Temp Settings (1-5)
Put the themistor BACK where it was (OEM Position--middle of fin)
Make sure the tip is just protruding above top of clip and it is secure against the Fin

Moving the thermistor UP/DOWN is for those Models that use an 'AUTO TEMP CONTROL' (no temp setting adjustments)
NOT your Model


I forgot to mention, I verified that the chimney did not have any obstructions a long time ago when I first started troubleshooting this. I have been lazy and this has been a problem for a while now. Beyond that, the area behind the fridge is quite clean and unobstructed. Insulation is where it should be, no bird nests [emoticon], the screen on the top vent is intact, checked when I installed the fan back there running to a solar panel on top of the vent cover, so nothing has gotten in there to chew things up. So I am pretty sure I do not have an external obstruction.

I'm having trouble with the concept that the thermistor could provide the correct resistance and still be bad. Its function is to provide a certain number of ohms of resistance back to the board. If I plugged my multimeter into the ends of the wires where they plug into the board and the ohms check out, how can the thermistor still be bad? Believe me, I WANT it to be a bad thermistor. But I don't see how. Further detail on that: When I first hooked up my meter the fridge temp was about 40 (had been 35 until I opened the door), and the thermistor was reading about 6500 ohms roughly. I wrapped my hand around the tip of the thermistor for about 30 seconds to warm it up and checked the reading again and it had dropped to about 5000-ish. Then I dunked it in the ice water and watched the numbers on the meter start to rise. After about 10 minutes it had settled at 9370, with the occasional twitch of about 10 ohms either direction.

I will check the fridge tonight after the thermistor has been unplugged for 12 hours.
If the fridge has not responded as expected for a bad thermistor I will see about plugging those leads directly into 120V (I will remove shore power first, plug them in there carefully, and then re-apply power.) and give it another 18 hours. Would just do 12 but ambient temps are pretty low this time of year here so I want to see if it stays cold when the sun comes up. Should have gotten around to this testing sooner.

Thank you for the additional testing steps to try. And I'll put my thermistor and clip back where it belongs, thanks.

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