# dometic fridge melting fuse on 12 v



## ozwhit (Feb 29, 2008)

hi all , my dometic 3 way is playing up on 12 v , its melted 2 fuses on our recent trip , so im now just using it on gas or 240 , the model is rm6501. in a 03 rapido , fuse was a 20 amp ,thanlks in advance gary


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## cabby (May 14, 2005)

Hi there Gary,This sounds more like a professional electrician is needed to check the wiring and see if there is a short along the line. Does the fuse blow quickly or over a period of time.
If we knew your location, as in town, we may have an idea of who could help you.
Unless of course the vehicle is under warranty.

cabby


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## Pudsey_Bear (Sep 25, 2008)

Hi Gary, we had this fridge in the last van, best we ever had, and miss it, but it was very reliable.

It does seem like a short, so take off the lower vent and see if you can see anything obvious, trace as much of the wiring as possible, the 12v wiring should end up at a split charge relay somewhere, usually near the VB.

A wiring diagram would help you a lot, one other thing, have a you had the van a while or just got it, I'm just thinking previous owner may have put too small size fuse in, but that's a long shot, don't be tempted to fit larger than required though.


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## BrianJP (Sep 17, 2010)

You need to measure the current being drawn by the Fridge if you have manual for it it should say.probably around 10 amps in your case. Ideally you will need a clamp meter ( you can get one from Maplin for around £40).
You may find that the current drawn is correct.Problem is that if you run the fridge on12v for long periods the fuse will get quite warm.
I had same problem. The fuse/dis board is under the bed with a cover over it.When driving for long periods 4 hours at least the fuse got so hot that it started to melt the surrounding plastic case.
The Fridge is drawing the correct current,in my case 16amps and fused at 30amps. With a temperature probe I found that the fuse warms up to 30°c above ambient temerature.
I proved this was normal conditions by bypassing the fuse board to the fridge with an in line fuse which heated up just the same.
I resolved the issue by extending the fuse position out of the board with an in line fuse .This allows for better ventilation and at least stops the plastic board case from melting.
On a recent return trip to Spain in air temp of 35°c + it worked well with problems.
Hope this info helps.I wouldn't waste your money on mh/caravan tech I doubt they will be much help.


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## gaspode (May 9, 2005)

I'm confused by the term "melted".

So is it blowing the fuse or is it melting the plastic fuse carrier?

If it blows the fuse then you have a short or the 12v heating element is breaking down.
If the plastic carrier is melting then you have a high resistance connection on the fuse board terminals - quite a common problem.


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## Pudsey_Bear (Sep 25, 2008)

BrianJP said:


> You need to measure the current being drawn by the Fridge if you have manual for it it should say.probably around 10 amps in your case. Ideally you will need a clamp meter ( you can get one from Maplin for around £40).
> You may find that the current drawn is correct.Problem is that if you run the fridge on12v for long periods the fuse will get quite warm.
> I had same problem. The fuse/dis board is under the bed with a cover over it.When driving for long periods 4 hours at least the fuse got so hot that it started to melt the surrounding plastic case.
> The Fridge is drawing the correct current,in my case 16amps and fused at 30amps. With a temperature probe I found that the fuse warms up to 30°c above ambient temerature.
> ...


I think your 10amps is pretty much on the mark.

*Link to my manual which is almost identical.*

Just refreshed my memory and cable should be 10mm2, fuse should be 20 amp, so the fuse you have is correct I think.

Out of curiosity where is the fuse sited, it should be as close to the supply as possible.

.


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## BrianJP (Sep 17, 2010)

One thing I forgot of course is there should be a label inside he fridge with he current rating on it.


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## BrianJP (Sep 17, 2010)

ozwhit said:


> hi all , my dometic 3 way is playing up on 12 v , its melted 2 fuses on our recent trip , so im now just using it on gas or 240 , the model is rm6501. in a 03 rapido , fuse was a 20 amp ,thanlks in advance gary


I thought at first your fridge was s smaller model but I realise it's similar to my rm7501.
I just looked up tech data for your rm6501 and it draws 175w which is roughly 14.5amps.
I would say it is under fused at 20a and should have 30a fuse. For example my fridge draws the same current and Rapid state 30a fuse .???


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## ozwhit (Feb 29, 2008)

hi all thanks for the replies .the fuse itself melted and is situated on the scheiber fuse board , i put the second fuse in, the relay was chattering , but this was on tickover ,i wiggled the fuse and it stopped ,we carried on , but the fuse had done the same . the earth connections to the fridge , are very rusty , il lcheck for shorting as well .thanks again gary


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## gaspode (May 9, 2005)

Very much sounds like a high resistance connection at the fuse board to me. You're getting an intermittent connection between the fuse and its holder which is generating heat which in turn melts the plastic fuse body. Clean the connections carefully where the fuse fits into the fuse board by using one of the wife's fine grade nail emery boards, then try again. Possibility is that you may need to replace the fuse board contacts or indeed the fuse board itself.


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## Pudsey_Bear (Sep 25, 2008)

ozwhit said:


> hi all thanks for the replies .the fuse itself melted and is situated on the scheiber fuse board , i put the second fuse in, the relay was chattering , but this was on tickover ,i wiggled the fuse and it stopped ,we carried on , but the fuse had done the same . the earth connections to the fridge , are very rusty , il lcheck for shorting as well .thanks again gary


I would if possible make a substitute earth lead, maybe an old jump lead or similar, direct to either the chassis or the LB -ve terminal and see if it still blows.


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## BrianJP (Sep 17, 2010)

Sorry to repeat myself but you actually need to measure the current being drawn by the Fridge to determine if there is a fault before you start replacing wiring .Get a clamp meter to do this .Your fridge should draw 14.5amps .


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## ozwhit (Feb 29, 2008)

hi all some pics of fuses , not sure about the furry one , looks like the fridge fuse has got really hot .


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## gaspode (May 9, 2005)

ozwhit said:


> hi all some pics of fuses , not sure about the furry one , looks like the fridge fuse has got really hot .


It certainly has - and the solder has melted through from the U/S of the PCB.

So - the fridge is either drawing a huge current (but if it was the fuse would blow not melt) or there is a high resistance at the soldered joint to the PCB.You need to remove the PCB and re-solder the joint with the fuse holder on the rear. There was probably a dry joint there from new. Hopefully that should clear the problem. While you're at it, re-solder all the joints on the board, if one was bad then others will probably be the same, it only takes a few minutes to do them once you get the hang of it.


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## mike800966 (May 1, 2005)

Fully agree with the advice given having just had similar problems with elderly Land Rover wiring, in this case with headlamp fuse holders which drove me nuts for a couple of hours. 
Just to explain, especially at these kind of currents, the resistance of the contacts in the fuse carrier will then generate heat. This usually softens the carrier plastic and worsens the connection thereby generating more heat until it burns out the connection altogether.
I wouldn't rush to change the fuseboard if it can be avoided but you will need to be sure of the current taken and I would reorganise that circuit, with the correct size of cable via a good quality separate fuse holder. Road pro did them or a marine type supplier would do them you need good contacts and a stable base 
The good ones tend to advertise as being gold plated to prevent oxidation of the contact surface .
Best of luck


Mike


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## Pudsey_Bear (Sep 25, 2008)

There's deffo something very wrong somewhere.


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## ozwhit (Feb 29, 2008)

hi all ,great replies as usual ,im going to investigate further ,will let you know the cause and the cure , regrds gary


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## Jezport (Jun 19, 2008)

You need to remember that you can set your van on fire with a 12V fault. So find it dont just increase the fuse value. Start at the fuse end and work towards the fridge then if you cant trace the wiring further then head back from the heating element on the fridge back checking all plugs and connections. Having said that I would suspect the fuse board first then the 12V element connector or element itself.


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## BrianJP (Sep 17, 2010)

This is the last time I will repeat the main point in my original post (speaking as an electrical/telecoms engineer for over 30years) . You need to check what current the fridge is drawing (preferably with a clamp meter) before you can establish what and where any fault may be. I checked and your fridge should draw around 14.6amps


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## Penquin (Oct 15, 2007)

IMO you have been given VERY sound expert advice, check the current is NOT excessive and locate where the fault may be - Gaspode's suggestion may well be correct as the fuse does not appear to have blown, simply melted.

You have been given advice from members who can be regarded as having a professional qualification and a vast amount of knowledge and experience in exactly the problem that you have encountered, only a fool would disregard such sage advice and that category is not suited to your personality.

Check then correct, not the other way round.

Dave


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## ozwhit (Feb 29, 2008)

hi all , clampmeter arriving tomo, ill check the draw and ,thanks brianjp for checking current draw , the scheiber relay is non serviceable ,so when ive found the cause , itll need renewing , ive been on the scheiber site and found the relevant replacement part , 
hopefully my findings may help someone else , many thanks gary


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## ozwhit (Feb 29, 2008)

hi all , just a quick update , auto electrician out today , he checked everything ,draw on fuse was 14.7 on meter , the fuse was a 15 and not 20 as i said , which he said was underrated ,replaced with 20 , the scheiber fuse block was also checked and found to be working correctly, the cause he could possibly underrated fuse , bad contact in fuse holder causing fuse to heat up , the ambient temp on our last travels was in excess of 30c , so fridge would have been working hard on 12v . so watch this space , thanks for everbodys input , , im sure itll needed again , regards gary


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