Dometic RMDT8505 fridge freezer - not cooling on Mains Electric

Abacist

Abacist

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N & B Arto 88F Tag
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This works fine on both gas and 12 volts but is not working on 240 mains voltage, or if it is, it is not noticeably performing any cooling or freezing function.

The unit does not display any of the handbook error lights or beeps but seems happy to apparently operate on the mains button.

The history of the vehicle is that we bought it in August 2018 after little use by the 2 previous registered keepers and shortly thereafter the mains side stopped working. When in Germany visiting the N + B factory they arranged for a Dometic engineer to service the fridge/freezer and he replaced both mains heating elements. The fridge/freezer then worked for some time but stopped working again when we came to use it in 2019. Since then we have either been in lockdown or have used it on 12 volts or gas only.

I have today checked it over again. It is definitely running on mains but not producing any error flashing lights or beeps but is certainly not cooling or freezing.

We would like to get it fixed but 2 dealers have now turned us down for either not feeling capable or are too busy. I have just sent an enquiry to another Dometic Service agent.

I am wondering if anyone on here has any ide what might be wrong.
 
If it cools on the two other power sources then either the a.c. heating element(s?) have failed or they are not being provided with a.c. power.

Are you able/competent to use a meter to check for 240V at the heating element terminal block?

Ian
 
bigtwin said:
If it cools on the two other power sources then either the a.c. heating element(s?) have failed or they are not being provided with a.c. power.

Are you able/competent to use a meter to check for 240V at the heating element terminal block?

Ian
Click to expand...
Hi Ian
Having read the Dometic manual for the fridge it is supposed to have flashing lights and beeps if the elements have failed which it is not doing so I wondered if it could be something else, especially as the heating elements have not long been changed. The german guy who changed the elements did it with his hands up the back of the fridge, blind, through the bottom vent. I have looked with a mirror and am having trouble seeing where the ends of the elements are!
 
I would expect the elements to be terminated in, unsurprisingly, a terminal block that ought to be accessible behind the lower fridge vent. The elements may not have failed it may simply be that something else has failed. Establishing whether or not a supply is present at the element/terminal block will help diagnose the problem.

However, if you are unfamiliar with electrics perhaps it‘s best to leave investigation to someone better qualified.

Ian
 
Does the fridge have a light? Is it working?

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bigtwin said:
I would expect the elements to be terminated in, unsurprisingly, a terminal block that ought to be accessible behind the lower fridge vent. The elements may not have failed it may simply be that something else has failed. Establishing whether or not a supply is present at the element/terminal block will help diagnose the problem.

However, if you are unfamiliar with electrics perhaps it‘s best to leave investigation to someone better qualified.

Ian
Click to expand...
OK I will check for power behind the fridge.
 
Must have been fixed by a top quality engineer, how did he manage to change 2 elements the 8505 only has one.

If its not the element its most lightly the black unit on the back of the fridge it controls the power switching & gas ignition. Common fault on the 8505 not cheap around £200 not repairable as all the electronics inside are potted.

peterc10 had the same problem.
 
Lenny HB said:
Must have been fixed by a top quality engineer, how did he manage to change 2 elements the 8505 only has one.

If its not the element its most lightly the black unit on the back of the fridge it controls the power switching & gas ignition. Common fault on the 8505 not cheap around £200 not repairable as all the electronics inside are potted.

peterc10 had the same problem.
Click to expand...
Thanks Lenny
 
Lenny HB said:
Must have been fixed by a top quality engineer, how did he manage to change 2 elements the 8505 only has one.

If its not the element its most lightly the black unit on the back of the fridge it controls the power switching & gas ignition. Common fault on the 8505 not cheap around £200 not repairable as all the electronics inside are potted.

peterc10 had the same problem.
Click to expand...
With my problem the warning lights were flashing, which the Domestic manual suggested was a failed 240v element. Eventually found one with the help of Lenny HB but decided to get it fitted at a dealer. Turned out my dealer (Becks, now sadly closed) knew more about the fridge than Dometic did and quickly diagnosed that the black block had failed, simply by testing the output from it, or lack of it. This was such a common fault that they had one in stock.

£200 later it was fixed. The good news is that if it is the element on yours I have one I can sell you :LOL:

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I had a 230vac element failure on my 8 series on the Flair. No warning light, no nothing, just not cooling on 230vac. It was in warranty and we were in Portugal. I called local Dometic agent and mobile engineer came, he had zillions of different powered elements to cover the panoply of options Dometic produce. He checked the 230vac in to the fridge and at the element wire connections to prove continuity then the resistance across the element +ve and -ve and declared the element dead. He replaced it under warranty save for the call out charge of €25.
 
Right I've checked that there is AC voltage going into the black box but having trouble checking if there is anything coming out as I've not worked out how to get the white connector off that takes the power up to the element but its progress!

Also I had left it on overnight on EHU and it was in error mode this morning with red light flashing next to the on/off blue light and also the triangle with the exclamation mark.

I am trying Caradoc in Ivybridge who are supposed to be Dometic Service Approved.
 
I have same issue with my dometic RMD 8505 , no cooling on EHU or 12v with engine running . Lights on the panel are showing its cooling but in effect the fridge internal is ambient - I did once have the red flashing triangle fault light but not seen it for a while now.

Spoke to a local mobile eng, he's hoping to get element and electrical boxes one sale or return basis and check it out / replace as necessary ...

I did wonder if I should replace the heat sink paste at same time ..
 
Abacist said:
This works fine on both gas and 12 volts but is not working on 240 mains voltage, or if it is, it is not noticeably performing any cooling or freezing function.

The unit does not display any of the handbook error lights or beeps but seems happy to apparently operate on the mains button.

The history of the vehicle is that we bought it in August 2018 after little use by the 2 previous registered keepers and shortly thereafter the mains side stopped working. When in Germany visiting the N + B factory they arranged for a Dometic engineer to service the fridge/freezer and he replaced both mains heating elements. The fridge/freezer then worked for some time but stopped working again when we came to use it in 2019. Since then we have either been in lockdown or have used it on 12 volts or gas only.

I have today checked it over again. It is definitely running on mains but not producing any error flashing lights or beeps but is certainly not cooling or freezing.

We would like to get it fixed but 2 dealers have now turned us down for either not feeling capable or are too busy. I have just sent an enquiry to another Dometic Service agent.

I am wondering if anyone on here has any ide what might be wrong.
Click to expand...
The resistor is faulty happened to us
 
Oh I do hope that this is the answer to my fridge problem. Please excuse my ignorance but what and where is the resistor?

I had a the fridge checked out by DMS after Stoneleigh but showed me it was working and cooling on mains by checking both the black block box brick on the back and the heating element. So its an intermittent problem by the seem of it but I can’t get it to work whenever I try!

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I had a similar problem with mine, intermittent operation on 230v. I found a poor connection between the 230v element and the power supply. If you have a clamp meter it's possible to check if the element is drawing power by using the clamp meter around the live cable to the element, approximately 0.79 amps at 240 volts when working correctly.
 
Put the fridge on 240V. Take the outer fridge vent off. After an hour feel the base of the metal flue. If its NOT HOT your 240V element is bad.
Another test is to test the ampage drawn when the fridge is OFF then re-tested on 240V.
Another test is if the 240V element is removed from the fridge and a 240V plug is fitted just to the element then if the 240V element becomes HOT the element is ok and it's something else.
 
Campervan_man said:
Put the fridge on 240V. Take the outer fridge vent off. After an hour feel the base of the metal flue. If its NOT HOT your 240V element is bad.
Click to expand...
Not necessarily. I made that mistake, see my post #10 above, and I still have the new element in my garage at home to prove it

My advice would be to always check the 240v output from the black electronic brick first before buying a new element and struggling to change it. According to the guy in the dealers the electronic brick breaks down much more than the element.

PS anybody want to buy an unused new element for a Dometic RMDT 8505 ...................................... ;) :ROFLMAO:

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bigtwin said:
Couldn’t agree more; i’d be very surprised if there is a ‘resistor’ anywhere that would affect both the a.c. and the d.c. elements.
Click to expand...
bigtwin said:
Couldn’t agree more; i’d be very surprised if there is a ‘resistor’ anywhere that would affect both the a.c. and the d.c. elements.

Ian
Click to expand...
It’s a cable thing near the bottom of fridge freezer Autostar mechanic has ordered one and at present we are on gas till week tomorrow I’m in Spain. Works fine on 12 volt too he called it mains resistor cost 70 euro
 
lucylocketz said:
It’s a cable thing near the bottom of fridge freezer Autostar mechanic has ordered one and at present we are on gas till week tomorrow I’m in Spain. Works fine on 12 volt too he called it mains resistor cost 70 euro
Click to expand...
Can you post a photo please.
 
did you resolve this issue?

I have very similar issue with mine. Got the van home, all seemed fine. Flashing red light on fridge (Dometic 8505) . turned off and on discussions with Nikki was it working or not. Agreed it was. Went on 2 week break, worked fine as far as we can tell including 5 nights in hot heat on electric.

come home, washed the van and then the same. Warning light of the blue flashing light suggesting the door isn't shut but it is. Eventually after several resets got that to stop, but then it's not cooling on electric again? works on gas 12v no problem.
 
Well, looks like I'm talking to myself. But today an engineer came out and said the 240 element is working fine and tested it. He thinks it might be the rcb (black box) but can't guarantee it, neither could dometic who he spoke with who seemed clueless.
 
The black box is an electronics module the does the gas ignition and switches 12v and 240v power.

They are prone to failure particularly the eairler ones pre 2017.
The later ones have a label on them saying Polyfuses or something similar.
 
Lenny HB said:
The black box is an electronics module the does the gas ignition and switches 12v and 240v power.

They are prone to failure particularly the eairler ones pre 2017.
The later ones have a label on them saying Polyfuses or something similar.
Click to expand...

Would failure prevent the fridge from cooling on 240?
 
haganap said:
Would failure prevent the fridge from cooling on 240?
Click to expand...
There is a post eairler on the thread when it did that, should be easy enough to check with a meter.

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