Dometic Fridge Fault - Weird Buzzing Noise on 12v

[darokika]

Hi everyone, new to the motorhome venture and this is my first post to you all. I have a 2006 Ducato Bessacarr E795, it has a Dometic RN7401L manual fridge installed and up until very recently it has been working absolutely fine. Yesterday I started my motorhome up and a loud buzzing sound came from the fridge, I opened the door and the sound seems to be coming from behind the control panel. The fridge was set to 12v so I turned it to 240v and the sound stopped, turned it back again to 12v and the noise returned. The fridge otherwise seems to be working fine on all 3 way options (12v, 240v and Gas) it just have this very annoying and loud buzzing noise on 12v. All 3 LEDs light up. I have checked all fuses and relays and they seem to be fine - (obviously as the fridge is operational). The best description of the noise is that it sounds like an electrical shorting noise but yet there seems to be no sign of any electrical short. Could this possibly be the control panel, dodgy relay or something else?

I have tried to upload a video file showing the noise but it seems that I can't

Any advice would be great.

 

[pappajohn]

Sounds like a faulty relay.
Especially if it has electromechanical/automotive type relays.

 

[darokika]

Thought that it might be, what would be the best way to check - there are 3 relays in all and they all seem physically fine

 

[Spawn_e_git]

Mine did this. Was a crap connection of the main 12v feed to thr fridge from the Elektrobloc thingy.

Find the large 12v power cable to the fridge and check its connection

 

[darokika]

Hi, thanks for that. It doesn't have an Elektrobloc as such (as far as I am aware) its more of a box with 4 fuses and 3 relays in the engine compartment. It actually stopped working completely on the 12v for a while (No LED or anything) and after I checked the fuses and relays it came back on but still with the annoying noise. So I'm thinking that it must be a relay breaking down somewhere there or even a dodgy feed wire/connection.

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[Spawn_e_git]

I felt the buzzer was part of the design to say "You've requested 12v and there is less than 12v"

get a meter and check the voltage at the fridge when it's switched on and engine running.

Mine only buzzed when the engine was running as this was when the Vcc signal was given to the fridge to start using thex12v.

 

[darokika]

I have made a quick YouTube video showing the noise - this may help

 

[Jimbohorlicks]

There was another thread on this with exactly the same noise, just do a search and see if it helps.

 

[Landy Andy]

At least it will be easy to locate when the fridge is out

 

[Jimbohorlicks]

In the other thread on this topic the OP said it was a shorting terminal in the main control block ,so just check that out. He had it sorted by Kenmore caravans if that helps.

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[pappajohn]

That is seriously loud and can't be a relay or short circuit....wrong kind of noise.
If it was a compressor fridge I'd say the motor was knackered but an absorption fridge has no moving parts.
Got me beat.

 

[GeoffnDee]

There is a wiring diagrams in the Resources section (top line of this page) on page4 of Motorhome technical articles for the 2003 Autotrails (Autotrail wiring 2014-07-28) which seems to be the same as 2006 and show the 3 x relays (on some models) and fuses that you have under the bonnet which may help explain their operation.
As suggested , check the connections on the control panel and also on the rear of the fridge.

 

[Riverbankannie]

This thread, exactly same noise

Dometic fridge/freezer

Anyone have any ideas what could be the probelm with our dometic fridge/freezer. When on 12volt while driving there is a buzzing noise coming from it. Changed the control panel but no difference does not do it all the time. Fridge works fine on gas and electric

www.motorhomefun.co.uk

 

[Spawn_e_git]

I have made a quick YouTube video showing the noise - this may help

Exactly the noise mine made.

Check the 12v high power supply. Put a meter across it and check it is 12v and remains at 12v. My guess is the voltage will drop down. There will be a 50amp or so fuse some where.

Pretty sure I posted in here when mine went

 

[Spawn_e_git]

Here is my thread and link to video.

Dometoc RM7655L Buzzer on 12v

Hi. Fridge model above. When selecting 12v the front panel emits a buzzing sound. To be honest it sounds like a very tired warning buzzer rather than a relay although I have known relays to make strange noises. Only started yesterday . makes the noise when engine running or not. Van is...

www.motorhomefun.co.uk

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[GeoffnDee]

darokika If you do check out the wiring diagrams in Resources make sure you check the one I pointed out not the other Sargent system Autotrail wiring for later models as they are very different.
There is also information, including a wiring diagram, for your fridge on page 3 of Manuals for Motorhome stuff in resources

 

[darokika]

Hi GeoffnDee, thank you for pointing me towards the wiring diagrams, they do seem to be pretty much the same. I'm going to do a quick video of my set up and hopefully some one could advise.

 

[darokika]

This is my set up.

1. This is the only area that I can find separate fuses and relays that are not connected to the main part of the motorhome. The wiring that goes to these fuses/relays come from the same wiring loom leading from the alternator to the engine battery.
2. There are no relays or fuses at the very rear of the fridge
3. There is a 12v DC relay in with the ones I found - wondering it that is the culprit?
4. I have checked all fuses/relays and they are all clean (no burning, corrosion etc) All fuses tested with a multi meter and all good.
5. The wiring behind the fridge is completely sheathed, no connecting blocks etc making it very difficult to test.
6. I am assuming that the wiring which I hold in my hand is the 12v wiring?
7. Have tested the charging rate for the alternator and that sits at 14.6v

 

[GeoffnDee]

One of those relays is the fridge 12v heating element one, you could remove each one at a time (engine running) to find it and see if the noise stops, I think it may be the single one ,.
Are the fuse holders ok, the second inwards fuse looks like it may have been overheating?