Dometic fridge freezer 240v not working. (1 Viewer)

[knokinonabit]

Morning all.

As you can see by the thread title I have a problem.
I have had a quick scan around the forum and found loads of useful info (as usual) so have come up with a possible answer.
Hopefully someone will keep me right and agree/disagree with me and offer more useful advice.

The fridge is a Dometic AES type and until recently has worked very well.
The problem seems to me to be the 240v side as it works perfectly on gas.
At the moment I am not too sure about 12v as we only notice the problem when on hook up, when it is too late.
The freezer allows all of the contents to thaw and the fridge isn't as cold as it should be. ie it allows milk to go off and beer and wine to warm up.
Switching manually to gas has everything working as it should.

I have checked the MCB for the fridge and that is ok.
The fridge controls give no indication that something is wrong, that is, there are no warnings and everything is illuminated that should be.

The conclusion that I have arrived at is that the heater element has failed.

All advice and suggestions gratefully received, even the p**s taking ones.

 

[Techno]

You need to disconnect the element and do a continuity test across it. If it's duff it will be open circuit. If it was short circuited it would trip the circuit breaker. It should have some resistance if ok I don't know the exact figure.
If the element tests OK then it must be the control board

 

[knokinonabit]

@Techno do think that it is the element that is the problem ?

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[Techno]

It's a possibility and easy to check.

 

[knokinonabit]

It's a possibility and easy to check.

Only if you know where to look

I can only find one marked as 12v

 

[Techno]

Have a look at the back of the fridge. There will be two pairs of wires coming from the flue stack. One pair is the 12 volt the other the 230 volt. Trace them back to their connections

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[Techno]

Without having any details about your fridge it's not easy to do any more. There are a lot of models you know

 

[Techno]

See on mine for example. The 230 volt element wires are in that fat thin wall grey sleeve on the left with 2 thin brown wires and an earth. It connects on that board next to the main supply connection and will be switched by a relay on that pcb.
The 12 volt element wires have the same sleeving but the wires are much thicker.
IGNORE the foreground board

 

[knokinonabit]

@Techno thank you very much.
I will test that tomorrow as today is spoken for already.

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[jezport]

The plug from the fridge to the element can go dodgy, check the voltage at both sides of the plug to see if it is the problem. You can cut the plug off and connect directly. TURN MAINS OFF FIRST

 

[Techno]

You can cut the plug off and connect directly. TURN MAINS OFF FIRST

That's assuming you know which fridge we are dealing with. Not a good idea with some plugs

 

[knokinonabit]

Just to clarify a bit, it is the RMD 8555 AES model with separate fridge and freezer.
The 240v heater is rated at 190w and the 12v at 170w.
I have been searching the web and can't find any diagrams or even spare parts for sale for this model.

I will look into it properly tomorrow when I have had a poke around and tested it.
I have switched the mains electric off at the socket hidden in the cupboard underneath it and it switches to gas ok. Switch it back on and it switches back to 240v.
Unfortunately it isn't cooling on 240.

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[autorouter]

At the moment I am not too sure about 12v as we only notice the problem when on hook up, when it is too late.

On my AES fridge, if I set it to 12V (not AUTO) it runs on 12V, even if the mains is connected. I use it for example on ferry crossings. Or the gas has run out and the gas supplier is having one of those Spanish lunch breaks.... Be careful, it drains the battery in a few hours.

 

[Techno]

The 12 volt won't get to the element unless the fridge gets the D+ signal from the alternator that operates the relay on the PCB and on the 8555 an audible alarm will start if the 12 volt isn't there. i.e. engine not running

 

[autorouter]

Yet another case of something being too clever for its own good, I think. Mine has a controller like the one in Techno's picture - if I set it to 12V it runs on 12V, engine running or not.

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[Techno]

Yet another case of something being too clever for its own good, I think. Mine has a controller like the one in Techno's picture - if I set it to 12V it runs on 12V, engine running or not.

It's not installed correctly then. I don't know what model you have but where the fridge doesn't have its own relay the converter should fit a split charge relay to do the same.

 

[autorouter]

It's an RM7655 AES. There's a relay in the 12V habitation controller (EBL 101). It uses the D+ to switch the fridge 12V supply between the alternator and leisure batteries. The starter battery never gets used for the fridge.

 

[Techno]

It's an RM7655 AES. There's a relay in the 12V habitation controller (EBL 101). It uses the D+ to switch the fridge 12V supply between the alternator and leisure batteries. The starter battery never gets used for the fridge.

I think that facility on the electrobloc is only meant for use with compressor fridges not 3 way
@Jean-luc ?

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[knokinonabit]

@Techno I have set my multimeter to the 20k setting and tested the resistance across the heater element and I am getting a reading of 278.
Is this pointing the finger at the circuit board ?

 

[Techno]

@Techno I have set my multimeter to the 20k setting and tested the resistance across the heater element and I am getting a reading of 278.
Is this pointing the finger at the circuit board ?

Yes its not open circuit and 278 ohms sounds about right.
Assuming that 230 volts is reaching the pcb and the 12 volt control circuit is on

 

[knokinonabit]

Yes its not open circuit and 278 ohms sounds about right.
Assuming that 230 volts is reaching the pcb and the 12 volt control circuit is on

More testing

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[knokinonabit]

@Techno I have connected the heater plug back to the circuit board and turned the fridge on. It selected 230v and I tested at the heater plug using the two test openings in the plug.
It was showing 243v, so power is there.
Looks like the fridge will have to come out to get at the heater element.

 

[Techno]

Do you mean you have the voltage at the element terminals too?
The manual says that the front panel will report faulty elements with either
HE1 or HE2 illuminated

 

[knokinonabit]

The front panel isn't giving any indication of a fault at all.
That has me perplexed.
Yes, there is voltage at the element terminals.

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[Techno]

The front panel isn't giving any indication of a fault at all.
That has me perplexed.
Yes, there is voltage at the element terminals.

The PCB is OK then as it has switched the relay to feed to element.
Perhaps it is "on it's way out" I don't know what the specific resistance should be.
To get the element out you have to open the tin jacket around the flue and wiggle the element upwards out of it's tube.

The current draw being 0.83 amps @190watts should equate to 277 ohms so I don't understand. Are you sure the bottom of the cooler doesn't get hot?

 

[knokinonabit]

The red sleeve is the one that goes to the element from the PCB.
As you can see, it disappears up into the bodywork, so to get at the element the fridge has to be removed.
I think.

 

[knokinonabit]

@Techno I have contacted Dometic and explained the problem to them.
They are asking have I checked the amp draw of the heating element, but I haven't a clue how I should be doing that.
Can you tell me in lay mans terms what I need to do, and with what please.

They also asked if I could feel any warmth coming from it.
As it is buried in the MH body, the answer is no.

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[Techno]

You would need an ammeter preferably a clip on one.(for AC)
If you put your hand on the cooler to the left of the gas burner the pipes should be quite warm

 

[Techno]

This is my ammeter measuring DC on the 12 volt element

 

[knokinonabit]

@Techno thanks very much for that.
I think I know a man who has one of those and he is visiting tomorrow.
A quick phone call I think.

I will have a go at feeling for heat, but I'm not holding out much hope.
I will try in the morning.

Thanks very much for being so patient and helpful.

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