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Topic: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out (Read 334 times) previous topic - next topic
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Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Hi everyone,

Last week we had our alternator replaced in our 2006 MB.  Afterwards there were several issues:

-- No power at thermostat (resolved - replaced 7.5A thermostat fuse in the converter)
-- No power at Radio (resolved - replaced 10A fuse in the engine bay)
-- Generator has no indicator lights (I'll handle this later - there's 12V at the solenoid but that's as far as I've gotten so far, a control board is on order just in case)
-- Refer has no indicator lights or power.  After confirming 12V at the terminal located on the back next to the control board, I removed the control board cover and checked both fuses:  the 5A was fine, the 3A fuse was burnt and when replaced it burns out immediately.

I have several questions.  I know it's a lot, so please only address what you think may be relevant:

-- Is the alternator in our LD a special LD or RV version?  Or is it just the stock E-450 part?  Does that even matter?
How do house batteries get charged when driving? Is it:  Alternator -->  Converter --> Batteries?

-- Could there be a system-wide short that only affects lower-amp fuses?  The only fuse (so far) that keeps burning out is the 3A one.

-- Should there be 12V at the refer power terminal even if the house batteries are disconnected?

Additional notes:

-- The replacement 3A fuses I am using are from an auto parts and are the same girth but slightly longer than the original.  The clamps on the board only grab about half of the metal tips.  Although the fuse is longer it doesn't interfere with other components on the board.

-- The house batteries are relatively new and were adequately charged, I think there was about 13 Volts when I tested them.

-- I disconnected the house batteries (before the alternator repair) using the plastic red key on the switch above the batteries.

-- The shop I had it done at is trustworthy but not an RV repair shop.

-- The generator was working prior to the alternator replacement.

-- I am not sure if the refer was working immediately before the repair.  It was working on our last outing a couple of months ago.

-- The thermostat was working before the repair.  I ran the generator and AC while we were at the shop waiting for the tech to check the alternator.

Any information you can provide will be greatly appreciated.  I'm trying to resolve this before we leave on a short road trip.

Thanks in advance,
Danny

PS - In case anyone needs them, I've compiled the following part numbers:

Dometic Refrigerator Model# RM2662 Product# 921-14-41-34

Control Board:
    -- Original part #:  3850712013
    -- Replaced by part #:  3316348.900
Control Board 3A fuse:  3308897.010
Control Bord 5A fuse:  3308897.002
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #1 –
"How do house batteries get charged when driving? Is it:  Alternator -->  Converter --> Batteries?"

In that situation, the converter isn't involved. Its job is to convert 120 VAC to 12 VDC when you're plugged in or running the generator. When driving, the house batteries are charged thusly: Alternator --> Isolator --> Batteries

Andy
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #2 –
I also had trouble with my RM 2662. From a review of this site I figured it was the electrode since I could run on electric for awhile and then it would run on gas. Here is the part.  Dometic Refrigerator Electrode with 17" Wire Lead - Refrigerator Parts -... Actually bought on Amazon (well, bought two. Whenever I have an issue with a part I buy two. Fool me once, shame on you. Fool me twice ...... 😂).

Replacement was super easy. Fired up the fridge and it fired right up. Tried again a couple days later and fired right up.

I love this site!!!!!!!

Grateful Dave
Ruby, the red 2004 26' RK hauling Dave and Kristine hither and yon
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #3 –
The AES controller on Dometic RM 3601 required a 13.5 + volt signal from the key to allow 12 volt operation.
Rodney
1988 Mid Bath
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #4 –
Motors are constant power devices, as the voltage drops the amps increase to maintain the power level.  Most items are resistive device pointing to an over voltage situation  
Rodney
1988 Mid Bath
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #5 –
Quote from: dane2001  - 
Last week we had our alternator replaced in our 2006 MB.  Afterwards there were several issues:

-- No power at thermostat (resolved - replaced 7.5A thermostat fuse in the converter)
-- No power at Radio (resolved - replaced 10A fuse in the engine bay)
-- Generator has no indicator lights (I'll handle this later - there's 12V at the solenoid but that's as far as I've gotten so far, a control board is on order just in case)
-- Refer has no indicator lights or power.  After confirming 12V at the terminal located on the back next to the control board, I removed the control board cover and checked both fuses:  the 5A was fine, the 3A fuse was burnt and when replaced it burns out immediately.
-- Is the alternator in our LD a special LD or RV version?  Or is it just the stock E-450 part?  Does that even matter?
--How do house batteries get charged when driving? Is it:  Alternator -->  Converter --> Batteries?
--Could there be a system-wide short that only affects lower-amp fuses?  The only fuse (so far) that keeps burning out is the 3A one.
-- Should there be 12V at the refer power terminal even if the house batteries are disconnected?
-- I disconnected the house batteries (before the alternator repair) using the plastic red key on the switch above the batteries.
-- The generator was working prior to the alternator replacement.
-- I am not sure if the refer was working immediately before the repair.  It was working on our last outing a couple of months ago.
-- The thermostat was working before the repair.  I ran the generator and AC while we were at the shop waiting for the tech to check the alternator.
Dometic Refrigerator Model# RM2662 Product# 921-14-41-34

Were any of the above electrical issues present before the alternator was replaced?
Why was the alternator replaced?
What symptoms lead you to replace the alternator.

Not at all sure why you have so many burned fuses unless there was another electrical problem that allow the voltage to get too high.
Depending on the wiring, 12-volts can till be present at the Power Center when the coach battery is disconnected, with the power coming from the Converter, solar panels or possibly the battery isolator.
If something caused the alternator to stop regulating, and were t go into full output, it can produce a 100-volts or better, more than enough to burn fuses and circuit boards. When connected, the battery acts as a big voltage regulator, moderating voltage surges.
If the battery is turned off, during a surge, it cannot protect the 12-volt circuits from over-voltage.
Something might have happened during the alternator change, maybe. Without more information, were are just guessing.

On your model, power from the alternator is sent to the coach battery via the isolator, located under the hood.
The converter provides battery charging when the rig is connected to shore power or when the generator is running.
The solar is connected to the Power Center and its voltage is present whenever the sun is shining, unless its fuse is pulled.
The 160-amp alternator is the standard model, used in E450s.

The 3-amp fuse, in your Dometic RM2662, provides power to the interior light and the heating strip, around the perimeter of the main door.
Neither of them are required to run the refrigerator and the fuse can be left disconnected until the cause is found.

If you do need to change the refrigerator's board, get a Dinosaur board, it is built to a much higher standard than the stock Dometic board.
I believe  the RM2662 used board #3850415.01
Amazon.com: Dinosaur Electronics (3850415.01 REPLACEMENT) Replacement Board...

Larry
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #6 –
Larry,
Thank you.  I forgot how complicated something like a refrigerator is.
It also reminded me of my Grandfathers trick, Remove the battery cable while the engine is running to check the Alternnator output!!!! It worked well in the days of relay voltage requlators,  but maybe not in the day of modern sensitive electronics.

Also the Ford manual for externally  regulated charging sysems, back in the day (before 1991 atleast),  jumper B to F  on the regulator connector with a wire jumper with two male spades atached, to verify if the problem is the Alternator or the regulator.  That would allow full voltage to the field and maximize alternator output.  It is applicable to my '88MB, would that be the case on the newer F450?
Rodney
1988 Mid Bath
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #7 –
Thank you Larry, Rodney and everyone else that responded,

I'm sorry for not updating sooner, I was able to resolve both issues but I haven't figured out what caused it.

Regarding some of your questions, none of the issues were present prior to the alternator problem.

It all began when the engine wouldn't start after filling up at Costco gas station.  The volt gauge on the dash was really low and I needed to jump start it with a portable battery pack.

I immediately called the mechanic and started driving, it's about 2 miles away from where I was.  On the way I lost all power to windows and even the gauge cluster, but the engine never shut off even though I noticed intermittent periods of decreased power.

After changing the control board in the fridge (on Thursday) and generator (Friday) everything is functioning normally.  I used this article for instructions on accessing and replacing the generator control board:

The Lazy Daze Companion: Generator - Replacing Onan 4000 Microquiet Fuel...


 
Re: Dometic Refrigerator Model RM2662 - 3A Fuse in Control Board keeps burning out
Reply #8 –
Glad everything is working again.
Sure wish I had a clue why the fuses blew and the generator's control board died.
A dead or dying alternator does not normally cause symptoms like this.

Larry

Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze