problem with auto select mode on dometic fridge

[le canichot depang]

We have just taken delivery of our 2008 Autocruise Startrail and have noticed a fault with the auto select mode with the fridge. It works fine when being operated manually on all three settings, however if we have it on the auto select mode, it will run on 240 when plugged into mains, switching to gas when we unplug the 240 supply, however when we start the engine it does not switch over to 12v but remains on gas.

We have tried it having the fridge switched to off mode, then starting the engine and selecting the auto mode but it immediately selects and ignites the gas which is obviously wrong, also tried turning the setting to auto select before starting the engine and it still results in the gas being ignited, it would seem that there is something that is not wired correctly between the 12v and engine possibly, however we have no wiring diagram supplied and cannot check it, no fuses have blown in the main fuse panel, has anyone with electrical experience any ideas - any help would be appreciated - thanks (?)

[davenewellhome]

Maybe a silly suggestion but try turning the gas off? If there's no gas it can't ignite and will then turn to 12Volt.

 

D.

[Patricia]

I have been informed by a fireman that if a motohome is involved in an accident the first thing the fire team have to do is to ascertain whether the gas is on - if it is they inform the insurers and it voids the insurance. I don't know whether anyone else can support this but anyway I always turn off the gas before moving the vehicle just in case.

[le canichot depang]

Thanks, yes that does sort of solve it but it still doesn't answer why it won't switch automatically, the idea behind the auto select mode is so that it automatically detects the correct power to use withour having to manually select, also for occasions where you might be away from your vehicle when there is a power cut so the gas will be switched on to keep the fridge cold then if the power resulmes it will go back to 240, also for instance in a service station there is an automatic 15 minute delay before the gas is ignited because the engine has been switched off as it is dangerous/forbidden to light gas in a fuel station, it seems pretty useless to fit such a system unless there are fail safe devices which are activated for certain situations - when on the road the gas supply should be automatically isolated so that it cannot ignite - surely such a system must have been passed by whatever safety council is responsible and insurance groups would have been advised before it was passed.

 

 

 

 

 

 

[Patricia]

My Dometic fridge/freezer is automatic with no manual opperation. It is programmed to search for electric in preference to gas but switches automatically to 12V when moving. So the automatic order of preference is 12V, 240 then gas. I find mine is difficult to light on gas if it has not been used for some time. With regards to isolating the gas supply I have to do this by turning off the bottle.

 

I must admit that this is confusing as my heater states quite clearly that it can be used while travelling!

[le canichot depang]

Our fridge freezer definately has the option of manualy selecting the power source or putting it on auto select - reading in the manual I suspect that the 12v supply should be wired through the battery and alternator so that when the engine is started it detects this (creates a ring) and switches to the 12v mode, however if only wired to the battery it would not detect this and think that it is just the 240 supply that has been disabled and automatically operate on gas. Anyway too late to think about it now, we will use the manual mode for the time being and when the van has its first service advise them to look at it - night night and thanks for the chat

 

 

 

[davenewellhome]

I don't have an operating manual for the AES fridges but I was under the impression that the priority for energy selection was 240V first, then gas and then 12 volt. Therefore if gas is available it would choose that power source even if the engine were running. This makes sense to me as you don't really want the fridge to switch from gas to 12 volts if you've just started the engine to charge up your batteries for example, or to reposition your van on your pitch perhaps.

 

Before you leave your pitch to move on you should turn off your gas at the cylinder unless you have something like Truma's Secu motion system fitted to allow for safe operation of a heater.

 

Surely, therefore, there is no need to use "manual" energy selection mode 'cos if you turn the gas off at the cylinder then the fridge will switch to 12 volt operation.

 

D.

[Derek Uzzell]

The 'energy source' priority order for the latest Dometic AES fridges (when switched to Auto mode) is

 

1. Solar (12V DC)

2. 230V AC

3. 12V DC

4. LPG

 

So (assuming the motorhome has no solar system installed), if the vehicle is hooked up to a mains-supply (needs to be 200V minimum), the fridge should choose that as the first option. If no >200V mains supply is available and the vehicle's motor is NOT running, then the fridge should seek to run on LPG. When the motorhome's engine is started then the fridge should automatically switch from LPG to 12V. It should be apparent which energy source has been selected by checking which control-knob LED is illuminated and there is a 12V-to-LPG 'safety delay' as has already been mentioned.

 

According to my Dometic manual there is a variation between the wiring of AES and non-AES fridges. This involves an extra connection for the AES-type linking the fridge to the 'D+' alternator signal. It seems reasonable to assume that, if this connection has not been correctly made (or is not being recognised by the fridge's electronics) then the fridge will not automatically select 12V DC operation when the motorhome's motor is started. As the remaining wiring connections are the same for AES and non-AES fridges, it also seems reasonable that an AES fridge will work exactly like a non-AES appliance when operated 'manually' (which apparently is what's happening in this instance).

 

(Purely as an aside, there's a thread on the MHF forum about Dometic non-AES fridge-freezers being wrongly wired on Hobby motorhomes and problems resulting. This is absolutely correct - the Hobby fridge-wiring differs from Dometic's instructions and it's difficult to see why the fridge/freezers in Hobbys should work at all. Nevertheless they do, as mine is wired in the Hobby manner, doesn't seem to mind and, as long as it keeps going, I'm not going to alter the original wiring even though it would take only a few minutes to do so. Funny things motorhomes...)

 

Patricia:

 

I'm wary of what you were told by a fireman regarding the insurance aspect. I can perhaps understand an insurer becoming peevish if, say, a motorhome involved in an accident went up in flames because the gas bottles had not been turned off, but I can't see why this factor should have any bearing otherwise.

 

Some years ago I researched for my own education the implications of using a motorhome's gas appliances while driving in the UK and was advised that there were no general rules prohibiting this. Specific rules Yes - not in tunnels, not at petrol stations, not on ferries - but no general UK prohibitions. It does need emphasising that other countries have different rules to ours.

 

I turn off my gas cylinders during ferry crossings, but other than that normally don't bother. As our motorcaravanning involves travelling around a lot, I'd otherwise be forever turning the bottles on and off. Plainly, if one has a 'smart' fridge, the gas bottle needs to be turned on continuously for the fridge to work as it was designed to do.

[davenewellhome]

Thank you Derek for a most enlightening post, I stand corrected on the operating modes of AES fridges and agree with Derek, the most likely explanation for your fridge's failure to function from 12 Volts is that the D+ signal is missing, possibly a fuse under the bonnet somewhere.

 

D.

[Patricia]

Derek thank you for your reply and advice - as always you are extremely helpful. I must admit that I used to leave the gas on before the conversation with the fireman ( and on occasions since when I inadvertently left it on during a ferry crossing) and was always confused by the Truma instructions. I have never tried travelling with the fire on, as I suspect the flame would blow out anyway, but taking your advice it would certainly save a cold, and usually wet and windy, visit to the outside gas box every time I stop.

[libby]

I'm very surprised that Derek suggests he drives around with his gas cylinder turned ON. Are you really suggesting the insurer would only be peeved if the vehicle was lost due to a fire when otherwise the problem might only have been a large dent in the gas locker door?

 

Definitely not a good idea. (if I've read him correctly).

 

This surely can suggest to new users there is 'no danger', and, being new users how's about if they drive into a garage for fuel with the gas alight, just because they forgot!

 

Patricia

 

Are you really suggesting your life is too unimportant to bother to turn off the gas just because its cold and windy, Oh dear young lady!

 

My life and survival is most important and I would NEVER travel even 1/4 mile with the gas on. Most cyclinder lockers than I've seen are very conveniently sited exactly at a sideways collision height.

 

Bill

[Mel B]

Whether you travel with the gas turned on at the bottle is up to each owner to decide. I must admit I used to be very insistent that all gas should be turned off at the bottle, having seen first hand what it is like to have a gas leak (and blowtorch!) in a motorhome (while stationary) I can tell you it is extremely frightening. However, the fault was not with the bottle, it was with a badly fitted (by dealer) gas BBQ point connection where it joined the original gas piping inside the motorhome ... back to the point ....

 

For those with AES fridges if the gas isn't turned on then what's the point of the fridge in the first place? It's very purpose is to choose the appropriate energy source. It will NOT go to gas whilst travelling (ie with the engine running) so should always only use 12v, assuming it is working correctly and that the battery has sufficient juice in it to run the fridge.

 

IMO you should NEVER attempt to travel with a gas appliance turned ON, such as a heater, no matter how safe you think it is, you cannot possibly know if the flue is working correctly (ie the fumes being blown back inside as you travel) and the danger of the flame being blown out.

 

I can also understand Patricia's comments about not having to keep turning the gas on and off at the bottle, especially when you travel around and are stop/starting, or have an AES fridge.

 

As for insurance, I have just read my policy and no-where is there any mention of gas bottles, never mind whether the gas is on or off. The only reference to gas bottles I have ever seen in previous insurances was whether or not they were included in the 'insured items', ie in case of theft etc. If the policy doesn't state they must be turned off, or it is against the last to travel with them turned on, then I don't believe that the insurance could refused to pay out if the time came ... I hope it never does! Perhaps some forum member from the insurance industry could comment?

 

 

 

[bob b]

As an ex-Fire Officer, we rarely had dealings with insurance companies following a fire. If the fire was large and represented a large loss to the insurance company, they may request an interview or a copy of the fire report, but wouldn't bother for a motorhome fire.

We also wouldn't inform the insurance company if the gas was turned on... as a matter of course.

The only time an insurance company would be aware of the gas being turned on, is if the gas was a contributary factor to the fire damage, and only then if they requested a copy of the fire report.

I always travel with the gas turned on and isolate the cylinder on my return home.

[Brian Kirby]

On why the fridge won't run on 12V, I'm with Derek.  It might be worth checking whether the habitation battery charging is working from the alternator, since a duff relay seems a possibility, and also checking for a missing, blown or incorrectly inserted 12V fuse.  However, as this is apparently a new, albeit late, van, why not take it back to the dealer and let them sort it out?

Re gas, again, so far as I am aware, Derek is right and there is no UK law requiring the gas to be isolated while driving.  However, I believe there is such a law in France.  I have seen numerous references to it, and we were specifically instructed to do this - without fail - when we hired in France. 

The exception is where the Truma "Drive Safe" (UK) or "Secumotion" (Europe) system is fitted.  This comprises pressure sensitive cut-off valves at the cylinder connection, and at the regulator.  If pressure is lost on the low pressure van system the regulator cut-off operates, and if a high pressure flexible is severed the cylinder cut-off operates.  It is intended to allow use of gas appliances while driving.  Oddly this practise seems to have been legal in Germany for years, so far as heating systems are concerned, despite which, so far as I know, there is no time delay on the Truma heaters to prevent their operation on filling stations, reflecting the way the Dometic fridges are controlled.

[le canichot depang]

A big thank you to everyone who replied, we will check the wiring to the alternator and see if there is a fuse and report back. We cannot go back to the dealer until on holiday next June due to living in Jersey - it is too expensive to go over just for that, but we have informed the dealer who has a note of it and will look at it when we are over in June. At least if we cannot sort it before then we can safely use it in the manual select mode which we know does work. - Once again thank you - such a knowledgable crowd you are :-D

[mirage]

I was going to post a rambling reply but "over complication" comes to mind

[Derek Uzzell]

Judy,

 

Suggest you begin your investigation by checking the wiring connections on the fridge itself to confirm they match the information given in Dometic's manual. As your fridge operates properly when switched manually to 12V, it's fair to assume that there's an 'alternator signal' reaching it to indicate that the motorhome's motor is running. If that's the case, then the problem may just be due to a loose wire at the fridge's terminal-blocks, or failure to lead a wire to the D+ connection on the terminal-block. (Perhaps the Autocruise technician wired up your fridge as if it were a non-AES model?)

 

Inspecting the fridge wiring connections usually only involves removing the lower exterior ventilation grille, but be careful when doing so as the larger grilles don't take kindly to rough treatment and the plastic can crack across the corners.

 

 

 

General:

 

The personal research I mentioned in my earlier posting's penultimate paragraph involved attempting to confirm the legality of using a gas-heater while driving when the heater (eg. a Truma C-Series appliance) had been specifically designed with that purpose in mind. I didn't concern myself with safety implications (which are plainly self-evident), I just wanted to determine whether or not, should I decide to do this, I would be committing an offence.

 

Truma (Germany) told me that (in the then EC group of countries) only two countries had laws that forbade the practice. The other countries either had laws that permitted it or had no laws prohibiting it. I know that one of the countries that legally forbade the practice was France but I can't recall the other (Denmark I think). I also asked the Caravan Club what the position was in the UK and was eventually advised that this country had no general prohibiting regulations, just specific ones (ferries, tunnels, etc.). The CC emphasised the risks of using gas-fuelled appliances en route and I wouldn't argue with that.

 

Like Brian, I've been occasionally told in France that it was a legal requirement there to turn off a leisure-vehicle's gas-bottles before driving, but I've never been convinced this was correct. While I've been perfectly comfortable accepting that running gas appliances in a moving vehicle was prohibited by French law, I've always considered that a 'gas-bottles must be turned off' regulation would be extremely hard to define satisfactorily. I've felt that gas-bottles-must-be-off was French urban received wisdom in that - like their 'must carry a set of spare bulbs' rule - it was widely believed to be true and made good sense, but wasn't actually a legal offence if you didn't do it. (I also pondered why, if gas-bottles-must-be-off was genuinely a French law, I'd never noticed French motorcaravanners doing it!)

 

The marketing in France of Truma's SecuMotion system also seems to give the lie to the idea that France has a gas-bottles-must-be-off regulation for leisure vehicles. Truma claims that SecuMotion complies with EC Directives 2001/56 CE and 2004/78 CE relating to motor-vehicle heating systems and thus permits Pan-European use of a gas heater while driving. I'm reasonably happy to accept that, because of these EC-wide motor vehicle Directives, a motorhome with SecuMotion can use its gas-heater legally while the vehicle is being driven in France, but I'm less sure this would be the case if France had a blanket gas-bottles-must-be-off law.

 

Anyway, the only way I'm going to be convinced that I'm legally obliged to have my motorhome's gas-bottles turned off while driving in France would be by reading the legislation that said this.