Refrigerator fuse issue

[GeoZ]

I'm asking this question for a friend that is not computer savvy. I hope you all don't mind but his issue is very frustrating and maybe a safety issue. He owns a 2019 Cougar 362RKS (since new) with a Dometic 2 way Model: RM1350SLMX refrigerator. He has had issues with the fuse (circled) on the attached photo. This fuse will get so hot that you cannot touch it. It melts the solder in the fuse and heats up the circuit board turning it brown where the fuse holders are. The fuse holders will loose the spring tension from getting hot. The fuse doesn't always blow but 115 volt power is lost at times and frig switches to gas. He finds that it is usually operating on gas. Fuse is a 5 amp. To eliminate the trailer wiring being an issue, frig has been operated on a separate cord connected to outside power source. Issue still present. This condition has existed since new. Circuit board and element have been changed with new and known good used parts by dealer. Still does it. I'm really concerned for my friend. Dealer is running out of options but has not mentioned replacement on entire unit. Any ideas??

[ChuckS]

RM1350 fridge in my Alpine for 9 years... Zero issues..

The 5A glass fuse is there for one thing only... to blow if there is a higher current draw across the 120 VAC heating elements or a direct short.

You stated dealer used known good components... Also there are TWO HEATING ELEMENTS in that stack for 120 VAC operation..

Has anyone bothered to actually use a meter and check the overall resistance of the two heating elements?

Since the source 120 power has been eliminated as an issue by using a different power cord to plug into then either the heating element terminal connections at J7 and J8 are loose or bad or J5 and J6 connections for 120 VAC are loose or bad... OR the connections on the PCB for the 120 VAC circuit have cold solder joints thus allowing excess current to draw without blowing the 5 amp fuse... I also hope the correct style 5A glass fuse was installed..

Personally ... I would NEVER install a used part in an RV fridge.. Who knows how long that part has been in service, its been subjected to heat and cold as well as a lot of vibration and shock while towing down these stellar roads we have...

[chuckster57]

Originally Posted by ChuckS

Personally ... I would NEVER install a used part in an RV fridge.. Who knows how long that part has been in service, its been subjected to heat and cold as well as a lot of vibration and shock while towing down these stellar roads we have...

I’m not sure his dealer is doing, but some of the shops I worked at had “test boards” that we would use to rule it out. There is test equipment available but most shops won’t spend the money and I dare say most techs doesn’t know how to use it even with the instructions.

[skids]

Is it possible that supplied AC voltage drops due to other appliances (like the air conditioner, microwave) through the same shore cable? I really don't know how the fridge works ... does it have a compressor motor (or is it absorption only)? I raise this question because of a recent statement that motors will draw more current when the voltage drops. This is just something that I am throwing out there for comment as I am not an electrician!

[chuckster57]

Originally Posted by skids

Is it possible that supplied AC voltage drops due to other appliances (like the air conditioner, microwave) through the same shore cable? I really don't know how the fridge works ... does it have a compressor motor (or is it absorption only)? I raise this question because of a recent statement that motors will draw more current when the voltage drops. This is just something that I am throwing out there for comment as I am not an electrician!

RV absorption fridges use heat to make cold. There is a heating element (or 2) or an LP burner. In Auto mode the control board will send 110VAC to the element(s) to boil the ammonia if shore power is present. If it isn’t the control board senses no AC voltage and opens the gas valve and ignites the burner.

That’s it in a nutshell.

[Kuimonster]

I am getting my board replaced by dometic because of a short of some kind in the board.
Same issue, fuse kept blowing on electric power but runs fine on propane. Waiting on the part to come in but this is good to know incase ours still has the issue. We had to wait 2 months to get it seen by the dealer and our warranty was 3 days overdue.... The dealer tried to get Dometic to replace the whole fridge but they won't and only approved the board change... Ill update once we get the board fixed in 3-4 weeks....

[chuckster57]

I’m not a fan of Dometics boards, high failure rate on the WH. Dinasour brand has an extremely low failure rate.

[Kuimonster]

Sucks is it wont be fixed before we go camping. So we need to pack coolers. Not a huge deal but sucks nonetheless.

[skids]

Originally Posted by chuckster57

RV absorption fridges use heat to make cold. There is a heating element (or 2) or an LP burner. In Auto mode the control board will send 110VAC to the element(s) to boil the ammonia if shore power is present. If it isn’t the control board senses no AC voltage and opens the gas valve and ignites the burner.

That’s it in a nutshell.

Thanks for the clarification Chuckster. With "residential" refrigerators out there, I wasn't sure.

[chuckster57]

Originally Posted by skids

Thanks for the clarification Chuckster. With "residential" refrigerators out there, I wasn't sure.

Your welcome, to make it even more fun for us fools that still work on RVs, there is “residential” like what’s in a S&B house and 12V compressor style ( like the residential but operates on 12VDC not 110VAC

[GeoZ]

It is my understanding that the used parts were only installed for test purposes and not a permanent fix. Unfortunately, the used board shows signs of failure now also. It is in the photo.

Thank you for all of the input and valuable info. Maybe I have enough to be dangerous!!

[mikec557]

Originally Posted by Kuimonster

I am getting my board replaced by dometic because of a short of some kind in the board.
Same issue, fuse kept blowing on electric power but runs fine on propane. Waiting on the part to come in but this is good to know incase ours still has the issue. We had to wait 2 months to get it seen by the dealer and our warranty was 3 days overdue.... The dealer tried to get Dometic to replace the whole fridge but they won't and only approved the board change... Ill update once we get the board fixed in 3-4 weeks....

I waited for dometic to replace our circuit board the first time it went out. It (and the entire RV) was less than a year old. That board then died in Just less than another year.

Next time you need one, buy one made by this company. I ordered mine through Amazon rather than directly from them because I could get it faster. We were full timing and getting it quickly was important.

Edited to remove info about coming with a cover. That was the circuit board for the water heater...

http://www.dinosaurelectronics.com/

[GeoZ]

Are there any test procedures or ohm reading specs for testing the elements that someone could furnish? I'm heading to u-tube. May find there??

[ChuckS]

Yes.. THERE are two heating elements on the Dometic RM1350

Attached image shows chart for overall resistance value to see on a good element


Link to service manual for RM1350

https://bryantrv.com/docs2/docs/Serv...,%20RM1350.pdf

[GeoZ]

Thank you ChuckS. Exactly what I was looking for.