Dometic Fridge Problems

[fordgrl99]

Hey, all! My first post here, so take it easy on me, ok? ;) I have read through so many threads and posts and watched so many videos that my eyes are crossed at this point. Seems like a common problem, but...
We have a 2016 Sprinter with a basic dometic fridge. We bought it new in early 2017. It’s permanently parked at a campground and is auto-leveling. We had zero problems summer of 17 or summer of 18. Halfway through summer of 19, we had a higher than normal electric bill. DH narrowed it down to the fridge, shut it off and electric went to slightly lower than normal usage. We finished last season using a cooler for the weekends we were there. Now that 2020 season has started, I really want to figure out what’s wrong. We turned it on on a Wed and went back on Fri for the weekend. Freezer was froze and fridge felt cool. We had some non perishables in it the entire weekend but by Sun it wasn’t even as cool as it felt on Fri, so we shut it off again. We have an appt for someone to come look at it, they charge $55 for service call, and then $140 per hour obviously not including parts. What troubleshooting steps would you take, in what order? DH checked thermistor and that didn’t seem to be the problem. He also attempted to switch over to propane and it didn’t seem to switch over, but I think that’s an entirely separate issue. I’ve been advised that something may be blocking the air flow and that we may need to install a fan. DH is a handy guy and a good mechanic, if we can determine the problem, he should be able to fix it. The appt is not until end of July and if we can fix before then, even better! Any help is much appreciated! We live an hour away, so I’m hoping to work on it next weekend. Thanks!
Edit to add when the fridge is cycling, there is a loud hum that I don’t remember it having those first couple of summers.

[flybouy]

The "hum" you are hearing is most likely the converter fan. It supplies 12vdc and charges the battery and the more load it's under the faster and loader the fan gets. The fridge uses 12vdc for the controls and for the gas valve solenoid and ignitor.

This is just a guess, but given your unit is 4+ years old I'd check the battery first. If the battery has a bad cell it will not take a charge and the converter will be working hard trying to charge it. At 4 years old the original battery has most likely given up.

[fordgrl99]

The "hum" you are hearing is most likely the converter fan. It supplies 12vdc and charges the battery and the more load it's under the faster and loader the fan gets. The fridge uses 12vdc for the controls and for the gas valve solenoid and ignitor.

This is just a guess, but given your unit is 4+ years old I'd check the battery first. If the battery has a bad cell it will not take a charge and the converter will be working hard trying to charge it. At 4 years old the original battery has most likely given up.

Hmm. So we did start having intermittent problems with the jacks about that same time...but help me understand how that works...if we are connected to electric, is the fridge still pulling from the battery? So the battery runs the controls and if the controls aren’t functioning the fridge isn’t getting its signals?
Thanks!!

[flybouy]

When you are plugged into shore power the converter (typically located behind the breaker panel) will charge the battery and thus both the battery and the converter supply the 12 vdc for the lights, fans (bathroom), slides, jacks, fridge controls, water heater controls, and outside antenna booster.

The battery is crucial when operating jacks and slides as the converter will not handle a heavy load (heavy amperage) of those motors. If the battery is shorted out, the converter can shut itself off or get damaged and destroyed.

Take the battery to a auto parts store and have it load tested or if you know how to use a mul;timeter disconnect the battery, let it set with no load for about an hour and check the voltage. It should be over 12 volts.

[ChuckS]

If your converter looks like the one in this link it is barely adequate for the job intended. It is low grade ... lousy heat sink and a noisy fan that runs almost anytime there is any load on the DC Bus...

I’d upgrade it after you test and verify that battery....

https://www.trekwood.com/products/1124974/Converter-Main-Board-Assembly-Complete-8955-ANP

I’d also DL the service manual for the DM2852 series and take a look at the heating elements for the 120 VAC side ... if one isn’t working it will increase your power bill..

The Propane side is also easy to troubleshoot. I’d be cleaning the igniter and flue considering it’s age and use

[chuckster57]

Is your fridge in a slide? If so the hum is probably the fan(s) mounted to the fridge to move air when the temp reaches a certain point at the top of the cooling unit. Does the fridge operate on both AC and LP? How did he test the thermistor?

[Bill-2020]

If your converter looks like the one in this link it is barely adequate for the job intended. It is low grade ... lousy heat sink and a noisy fan that runs almost anytime there is any load on the DC Bus...

If so, what should the OP upgrade to?

[ChuckS]

Much better converter than stock WFCO 8955 7nit


https://www.progressivedyn.com/rv/power-converters/inteli-power-4600-series/#features-and-downloads

[Bill-2020]

Much better converter than stock WFCO 8955 7nit


https://www.progressivedyn.com/rv/power-converters/inteli-power-4600-series/#features-and-downloads

Thanks, I'll keep this handy.