Reefer not working on AC

[SPARKLE19]

Shortly after initial purchase of new 2019 we experienced a failure of the reefer, I.e., it would not work on AC and we really did not test to see if it would operate on propane. Took trip to dealer and was amazed that the “technician “ went directly to the reefer control board and changed the fuse (I believe it is a 3 amp), did not test by connecting to AC power but pronounced it was good. I insisted that we test with power connected and , sure enough, it worked. Obviously a common occurrence. Now just in the last few days it has blown the fuse again. I am anticipating replacing with a slo-blo just to see if I can get some longevity. Reefer operates fine on propane. Anyone had similar experience?

[BayouBiker]

I have seen a few threads where the 120 fuse blows. Sometimes the input voltage is low, other times the daisy chain of GFI protected outlets have a weak connection in the loop. Other times addition of a high load appliance and less than perfect connections causes current to spike. I would look for these issues before changing the fuse.

[SPARKLE19]

Plot thickens! Did a bit more probing and removed the bad fuse, seems it is a 5 amp and now I understand that when the dealer tech changed the fuse out the first time he had removed a blown 1 amp and was confident the problem was solved. Turns out that it was until now and I’ll find a slo-blo and try again. Until then it’s running on gas and I think it uses very little so I should be alright. I also noticed the schematic on the bulkhead “duh” and it seems there is two 5 amp fuses on the board the other is a modern two prong plug in. I’m hoping the cause was a power fluctuation at the last campsite and all will be well.

[BayouBiker]

Yeah strange the original was not 5 amp. I suppose you could get a couple extra fuses and if it blows a couple more times then look for a connection issue.

[Bcc75]

I am having the same issue with my brand new Int. 25’. I replaced the blown fuse twice with the same fuse(3 amp glass). Then I isolated the refer from the trailer by unplugging the AC cord from the receptacle in the refrigerator compartment and plugged into a drop cord connected to a known reliable receptacle from my storage barn where I keep the trailer. It blew again after working briefly. The back panel of the refer seemed to get abnormally hot before the fuse blew. I took it to the dealer to fix this and other issues and they diagnosed as a bad heating element and control board. I’m not buying the control board because if the control board was bad then it shouldn’t work on LP right? But if works fine on LP.
The parts are on back order from Dometic due to COVID so we will have to wait and see if this fixes it but I have my doubts. I have checked all connections that I can visibly see.

[BayouBiker]

What model is your refrigerator? There are some sites online that provide some of the service bulletins and troubleshooting bulletins. The tech likely just followed the troubleshooting flowsheet. It would be best to confirm the diagnosis before proceeding. A bad heating element sounds right, I too wonder about the board. Part of the board is common to both modes and part of the board is specific to each so it is possible the board is also bad, but yet I still wonder how they came t this conclusion.

Also describe more clearly what part of the refrigerator was hot.

[Bcc75]

I’ll have to get the model # and get back to you on that. Probably tomorrow. The ‘chimney’ as I call it was hot. Hotter than normal I would say but the fan was running. I noticed the 2 wires going to the element were unplugged when I got back from the dealer so I assume they tested something. I have the trailer back now as there was no eta on the parts as they are on infinite back order. I didn’t want my trailer just sitting on their lot waiting on that. They already left my batteries on use mode and drained them during the 2 weeks that they had it.

[BayouBiker]

Ah well the chimney being excessively hot would match with an element that draws too much current and overheats so that's consistent. I'll watch for a follow-up tomorrow.

[GCinSC2]

Clamp on ammeter time and measure actual current draw for heating element only. Or use meter and measure element resistance.

Ohms law coming into play?

[Bcc75]

Originally Posted by BayouBiker

Ah well the chimney being excessively hot would match with an element that draws too much current and overheats so that's consistent. I'll watch for a follow-up tomorrow.

Brian
The refrigerator is dometic RM3762LBFX
So if I turn on in auto mode and test the prongs that go to the element in the control board and I get 120v hot to neutral, then the board should be ok correct?

[BayouBiker]

Here is a link to the service manual: https://myrvworks.com/wp-content/upl...ice-Manual.pdf. You can confirm the shop's diagnosis of the heating element by testing resistance. Page 10 indicates the element resistance should be 39-49 ohms, that would make operating current between 2 and 3.2 amps so the 5 amp fuse seems like the best choice. The 3 amp fuse is for the 12VDC control and gas operation. Check the heater element resistance to see if the shop got that part right.

To your question, 120 on the outputs would indicate the controller is doing what it is supposed to functionally. Page 13-15 describes how to test the board and says if you get 120 on the heater output, the board is fine. I am with you. The board is fine.

[Bcc75]

Originally Posted by BayouBiker

Here is a link to the service manual: https://myrvworks.com/wp-content/upl...ice-Manual.pdf. You can confirm the shop's diagnosis of the heating element by testing resistance. Page 10 indicates the element resistance should be 39-49 ohms, that would make operating current between 2 and 3.2 amps so the 5 amp fuse seems like the best choice. The 3 amp fuse is for the 12VDC control and gas operation. Check the heater element resistance to see if the shop got that part right.

To your question, 120 on the outputs would indicate the controller is doing what it is supposed to functionally. Page 13-15 describes how to test the board and says if you get 120 on the heater output, the board is fine. I am with you. The board is fine.

Thanks Brian. You are a wealth of information on these forums and I greatly appreciate it. Will do some testing and report back.

[NickWP]

I'm watching this thread. We have a 2021 27' flying cloud FBT with the same refrigerator and same problem. Just replaced the 5 amp fuse and it's working so far. Very interested in the progress and resolution.

[SVMC fc25]

Regarding whether or not the control board is bad, I do not have direct experience with refrigerator problem. However we have a 2019 FC 25 RBQ. The first time out with it, the hot water heater would work on electric but not on propane. I was able to determine that it was getting propane but would not ignite. Our dealer ordered and overnighted me a new control board. Once I installed it, the water heater worked on propane and electric. My point is that it is possible for either the electric or the propane section of the control board to be bad without the other section also being bad.
Steve

[SPARKLE19]

When I had the original problem with the reefer, I had just taken delivery on the unit a few weeks before so I took it back to dealer and did not attempt to troubleshoot. If I had done it myself I probably would have found the bad fuse, read the size on the body and replaced with a like item. I think I would have researched th label but..... when the cover is raised to see the fuse, you can’t see the label.

[SPARKLE19]

Update. Received new fuses (5 A slo-blo) and installed 48 hours ago, unit cooled to my standard operating temperature and is still on AUTO, that is, operating on AC. Have fingers crossed that problem was transient voltage fluctuation and all will be well!

[BayouBiker]

Nice! Good to know. Did you happen to check heater element resistance?

[SPARKLE19]

I did not, but will do that when I get back from upcoming short trip off grid. Also DW reminded me that a check of the water heater element for build up is in order.
Thanks all for input.