110V fridge draw ?

[Lanark Camper]

My Dometic fridge has always worked well. I just got the trailer out of storage yesterday. Today it’s quite warm and it’s struggling to get the fridge below 40°. Usually it’s been 34° to 36°. It’s is a warm day here, 90°. I have two small fans mounted inside to circulate air inside.

The fridge came from Escape with the fan in the outside cavity, I’ve heard it run before on hot days but not now ?

I’m only seeing one amp coming into the trailer on my shore power, that seems low but I don’t recall what it was in the past with just the fridge running.

I moved the temp sensor down to just below the bottom of the heat exchanger, too soon to tell if that will help.

I have frozen food in the freezer that seems ok.

So the freezer works. The pipes at the back of the fridge get very hot on both electric and propane.

The refrigerator is only 46 to 53°. I adjusted the temperature setting on the control panel to max. No difference. I moved the temperature sensor to the top of the aluminum heat exchanger, closest to the freezer compartment. I suspect it is this temperature sensor that is the problem.

Bob

 

[Lanark Camper]

I replaced the thermistor in the refrigerator but no change.

Freezer runs at 4°F while fridge is at 55°. Same on propane or electric. The electric heater draws 1.1 Amps.

Not sure what I can check next ?

Bob

 

[7Gentex]

I replaced the thermistor in the refrigerator but no change.

Freezer runs at 4°F while fridge is at 55°. Same on propane or electric. The electric heater draws 1.1 Amps.

Not sure what I can check next ?

Bob

What does your freezer section usually run?

Do you have anything in the fridge portion for "thermal mass"?

My fridge portion takes forever to cool off on "startup"......

My fridge portion also struggles when empty so I keep at least a gallon of water in there, and numerous "canned drinks" :whistling: in the door.

I believe that the cooling system is really a "one piece" deal, and if your freezer section is doing the job, the fridge should be as well?

Recovery time after opening a door is atrocious with an absorption unit as well...........

The outside fan may be a culprit - there doesn't seem to be a rhyme or reason when mine runs........thermostatic I guess.



?

 

[Mike Lewis]

My Dometic three-way fridge (since replaced with a compressor fridge) drew a whopping 14 amps when using shore power. FYI

 

[Lanark Camper]

What does your freezer section usually run?

Do you have anything in the fridge portion for "thermal mass"?

My fridge portion takes forever to cool off on "startup"......

My fridge portion also struggles when empty so I keep at least a gallon of water in there, and numerous "canned drinks" :whistling: in the door.

I believe that the cooling system is really a "one piece" deal, and if your freezer section is doing the job, the fridge should be as well?

Recovery time after opening a door is atrocious with an absorption unit as well...........

The outside fan may be a culprit - there doesn't seem to be a rhyme or reason when mine runs........thermostatic I guess.



?

Thanks so much for your help.

The refrigerator has always run well for us since new in 2019. Generally start it up in the driveway a day or two before heading out, after 24 hrs fill it with cold, frozen food and it’s all good. Typically the fridge runs around 38° and the freezer 0°. The fridge does come up when adding a few new drinks that were not chilled but it settles quickly.

The trailer is perfectly level.

Two years ago I added two small fans to the refrigerator just in front of the aluminum heat exchanger and that seemed to improve the recovery time of the refrigerator and more even temperature distribution.

Right now the freezer is running 4° and refrigerator 55°. It’s quite warm here, 80’s+. I added 24 ice cold bottles of water and it made no difference.

We do have the factory installed fan in rear compartment to improve air flow there. It’s on a thermostat and so far hasn’t run. It has in the past when temps exceeded 90°. As a test I removed the top and bottom grills on the outside of the trailer and placed a 24” box fan on high tight to the bottom opening. It made no difference at all.

I also assumed if the freezer was functional the fridge should be as well. The thermistor seems to be the temperature control to balance the freezer temp to fridge temp. I assumed replacing it would fix the problem but no joy from that.

All the electrical connections seem good. I measured the current draw on the AC heater with a clamp-on ammeter at 1.1 A, the manual says 1.5 A. Probably close enough ?

I’m leaving for two weeks tomorrow morning so I won’t work on it again until we get back. Fortunately I have a small 12V fridge I can bring and I can use the freezer in the Dometic,

I’m looking at buying a new control board next. Any experience with the Dinosaur Boards ?

Thanks again, Bob

 

[SRS]

Thanks so much for your help.

The refrigerator has always run well for us since new in 2019. Generally start it up in the driveway a day or two before heading out, after 24 hrs fill it with cold, frozen food and it’s all good. Typically the fridge runs around 38° and the freezer 0°. The fridge does come up when adding a few new drinks that were not chilled but it settles quickly.

The trailer is perfectly level.

Two years ago I added two small fans to the refrigerator just in front of the aluminum heat exchanger and that seemed to improve the recovery time of the refrigerator and more even temperature distribution.

Right now the freezer is running 4° and refrigerator 55°. It’s quite warm here, 80’s+. I added 24 ice cold bottles of water and it made no difference.

We do have the factory installed fan in rear compartment to improve air flow there. It’s on a thermostat and so far hasn’t run. It has in the past when temps exceeded 90°. As a test I removed the top and bottom grills on the outside of the trailer and placed a 24” box fan on high tight to the bottom opening. It made no difference at all.

I also assumed if the freezer was functional the fridge should be as well. The thermistor seems to be the temperature control to balance the freezer temp to fridge temp. I assumed replacing it would fix the problem but no joy from that.

All the electrical connections seem good. I measured the current draw on the AC heater with a clamp-on ammeter at 1.1 A, the manual says 1.5 A. Probably close enough ?

I’m leaving for two weeks tomorrow morning so I won’t work on it again until we get back. Fortunately I have a small 12V fridge I can bring and I can use the freezer in the Dometic,

I’m looking at buying a new control board next. Any experience with the Dinosaur Boards ?

Thanks again, Bob

I put a dinosaur board in may RM2454 and it works great. They also now have a replacement eyebrow board. I wonder if that might be the problem your having. Just a though FWIW. Possibly the settings on the eyebrow board are not being communicated to the control board and the frig is running on a lower setting. Not an electrician so I'm only guessing. Good luck.

 

[Lanark Camper]

Thanks for the information on the Dinosaur board.
Ours is also the 2454 model.
What were your symptoms of a bad board ?
Thanks

 

[SRS]

Thanks for the information on the Dinosaur board.
Ours is also the 2454 model.
What were your symptoms of a bad board ?
Thanks

Soon after getting my trailer, I began having problems with the frig staying lit in gas mode. One of my first mods I did was replacing the Escape installed gas regulator with a Marshal-Excelsior regulator. When the problem started, I took it to a Dometic authorized RV repair place which took 6 weeks for an open appointment and after $200 and no failure (sometimes it would run for 4-5 days and sometimes only a few hours) I decided that was a wast (Dometic doesn't pay for diagnostics under warranty). They also never checked the gas pressure which really is the first thing they should have done, I figured I was on my own. Being new to the trailer and frig I thought it was the control board and it was less expensive than going back to the RV shop. When that didn't solve the issue, I decided to get the tools, mainly an manometer, to measure the gas pressure. That turned out to be the problem because the gas pressure was 14" of WC. Adjusted the gas regulator down to about 12" WC and all has been fine since. I just left the dinosaur board in and I'm keeping the Dometic board as a spare.

 

[Chamberman]

I also assumed if the freezer was functional the fridge should be as well. The thermistor seems to be the temperature control to balance the freezer temp to fridge temp. I assumed replacing it would fix the problem but no joy from that.

All the electrical connections seem good. I measured the current draw on the AC heater with a clamp-on ammeter at 1.1 A, the manual says 1.5 A. Probably close enough ?

I’m leaving for two weeks tomorrow morning so I won’t work on it again until we get back. Fortunately I have a small 12V fridge I can bring and I can use the freezer in the Dometic,

I’m looking at buying a new control board next. Any experience with the Dinosaur Boards ?

Thanks again, Bob

1.1A seems too low if 1.5A is expected. Whats your incoming AC voltage level? Because these are purely resistive elements, the incoming AC voltage as delivered to the fridge will drive your ultimate AC heater current level. Also, If the AC heater element resistance has started to go up then the current will drop and the heating will not be sufficient.

Does your manual list the wattage rating for the heater elements in your fridge?

I'm assuming you have one of the smaller 3 - 5cu/ft Dometic models? Our 19 has the larger 2663 Dometic and I'd expect that Dometic uses a lower wattage heater element in the smaller models. The DC element part # in our fridge is listed as 275W in the manual. The AC element is listed as a 325W for our fridge. 325W @ 120VAC equates to 2.7A, and I haven't measured our fridge's AC current but I'd expect it to be within +/- 10% of that 2.7A number. Last week I was using the DC heater element to drain the 100aH LiFePo4 battery I installed this spring. I calculated the power for the DC heater element @ 293W with 13.1V being delivered from the battery. This is very close to expected for the wattage of the heater element versus the delivered DC voltage. More than 10% low and I'd be getting worried of a failing AC heater element or a relay contact failing.

Just FYI, The control board will not affect the heater current, only a bad relay contact (which very well may be mounted on the control board) or a high resistance in the heater element itself will cause a low current condition. Of course the ACV delivered to the trailer will also affect this current, if its extremely low then the current through the fridge heater will also be low. However, if you have the Progressive EMS any voltage below approx 107VAC will drop out the EMS contactor.

 

[Lanark Camper]

Well done !

So far I have not had any gas issues. I did buy a digital manometer right after buying the trailer, our first, and made up the standard flow test rig. Looked at the pressure and tweaked it a bit.

I only had a vague idea of how this refrigerator maintains the temperature, so actually enjoying the education. I’ve downloaded all the manuals I could from the Dometic website. Watched a few dozen YouTube videos. No answers but at least I know a bit more.

I do enjoy noodling my way through a puzzle but wish it was after a trip than just before

Bob

 

[Chamberman]

I would say that if the temp remains the same on ACV/DCV/Propane heating then your issue is elsewhere. Those are all 3 distinctly different heat sources.


The biggest thing to check is to see if the heater (whichever one you're using) is cycling off at the temp you're currently getting to. If the heater is cycling off, then that implies it is controlling at that temp. This says that possibly the control board is failing, especially since you replaced the thermistor. If the heater is remaining on constantly, especially at night, the the fridge isn't cooling down to the setpoint properly.

 

[Lanark Camper]

I would say that if the temp remains the same on ACV/DCV/Propane heating then your issue is elsewhere. Those are all 3 distinctly different heat sources.


The biggest thing to check is to see if the heater (whichever one you're using) is cycling off at the temp you're currently getting to. If the heater is cycling off, then that implies it is controlling at that temp. This says that possibly the control board is failing, especially since you replaced the thermistor. If the heater is remaining on constantly the the fridge isn't cooling down to the setpoint properly.

Thanks, excellent analysis ! I like the way you think.

I’ll see if I can rig up a way to see if the AC heater is on continuously or cycling.

Bob

 

[Chamberman]

I should elaborate on that last point,

If the fridge heater power or gas is staying on constantly, even at night, and not cycling off then its possible that the evaporative cooling system is not capable of reaching the setpoint temp because the cooling unit has failed. This can happen if the trailer has spent periods of time with the fridge powered ON but the trailer being off level by several degrees. In example, parked at a roadside rest stop, gas station, restaurant parking lot, etc. Parking the trailer seriously off level for more than 5 - 10 min at a time can cause the evaporative system to boil off all of the ammonia mixture, this causes a hard build-up to begin forming in the evaporative system. Eventually the build-up will choke off the evaporative plumbing and reduced cooling capacity is the result. There's lots of info & pictures online about this condition. There's even a system available to shut down your fridge when this condition begins to occur.


I've gotten in the habit of checking my bubble levels and shutting the fridge off when parked anywhere unlevel even for short periods because sometimes short periods turn into long periods.

 

[Chamberman]

Here's a link to that fridge protection system.

 

[Lanark Camper]

I’ve hooked up my clampon ammeter and watched it for 10 minutes, steady 1.27 to 1.29 current draw, no cycling.
The line voltage coming in is 115 V.

The heater is listed at 175 W, and 1.5 Amps.

The clampon meter is a bit variable depending on the position.

Right now the fridge is sitting at 44°, we have not opened the door since yesterday when it was loaded with some cold water bottles.

So it may be the refrigeration system is not functioning.

Bob

 

[Lanark Camper]

Here is what I’m seeing,

 

[Chamberman]

I'm not sure where your temp reading is coming from. Where is your temp probe located, right under the cooling fins in the fridge, the door or somewhere lower?

Yeah, 44 deg after sitting all night without opening the door and no significant load on it is very poor performance. Especially if your temp probe is right underneath the cooling fins. Our fridge will hit mid-30's overnight even in mid-summer heat here in Texas with outside temps only getting down to 80F overnight, 100F or more during the day.

 

[Chamberman]

Here is what I’m seeing,

Even with the somewhat low AC current readings, if you switch to propane and there's no appreciable difference in base fridge temps this says a problem exists. The propane setting on these fridges is generally considered to have the highest cooling capacity. If the propane burner also runs continuously but lower temps are not achieved inside the fridge then something is wrong elsewhere from the heaters themselves.

I'd begin to question the evaporative cooling unit itself.

 

[Lanark Camper]

It’s sitting on the second shelf, about middle of the fridge. I do have two small fans mounted in front of the heat exchanger.

Normally the fridge runs at 37-38° no problem under any conditions, so something died.

The problem with the cooling system clogging up from being run off level …..would this show up as reduced efficiency over time or a sudden failure that I’m seeing ?

We always level the trailer in each campsite.

Bob

 

[Lanark Camper]

Even with the somewhat low AC current readings, if you switch to propane and there's no appreciable difference in base fridge temps this says a problem exists. The propane setting on these fridges is generally considered to have the highest cooling capacity. If the propane burner also runs continuously but lower temps are not achieved inside the fridge then something is wrong elsewhere from the heaters themselves.

I'd begin to question the evaporative cooling unit itself.

Thanks, yes I switched to propane after your previous post, I’ll see if it makes any difference.

Bob