12v Fridge problems - any suggestions?

Discussion in 'Tech/Mech General' started by magicsurfbus, Mar 25, 2012.

  1. magicsurfbus

    magicsurfbus Funster

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    I have an ongoing problem with my CI Carioca 656's fridge in 12v mode - so far three different MH technicians and an auto electrician have looked into it and the problem remains. I would welcome any suggestions from the community as it's frankly getting on my nerves now.

    The fridge will only operate on 12v when the engine is running, and (typically) is linked to a control panel that monitors engine and leisure battery state. When I start the engine and monitor the voltage in the circuit there is a clear increase in voltage as the battery charger starts up. However, when the fridge is switched to 12v there is a steady drain on the voltage until it drops below the level where the control panel cuts off the fridge in order to preserve engine battery voltage. The fridge then repeatedly switches on and off as the voltage fluctuates around this cut off point.

    The engine battery is an 80Ah Bosch Silver battery bought new and fitted last July. The fridge is 7 years old. The charger is definitely putting power into the circuit when the engine runs. All the fuses have been checked and are OK. It seems to me there are three options here:

    1. I have a duff engine battery. The fridge problem pre-dates the new battery, which is why I had the original 2005 vintage battery replaced last summer. The voltage on the engine battery at rest is below 13v - that doesn't seem healthy to me. It's still under warranty so I might be able to get it replaced.

    2. The fridge is drawing more 12v current than normal - any thoughts on if/why that might be happening? It works fine on 230v and gas.

    3. There's something up with the charger. The new engine battery is a higher rating (80Ah) than the original. Could the charger simply not be up to the task of topping it up?

    The leisure battery is topped up by a charge-controlled 85W solar panel but I can't see any evidence that this is messing with the fridge or control panel.

    Any thoughts/opinions etc most welcome - we're off to France soon and we're not supposed to drive around with our fridge on gas over there. Plus I'm getting fed up with paying people to not find the solution.
     
  2. Terry

    Terry Funster

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    Hi I have not read all your post but the 12v fridge operation is only supposed to work when the engine is running :thumb: IT GOES THROUGH A RELAY THAT KICKS IN WHEN IT SENSORS THE VOLTAGE FROM ALTERNATOR
    terry
    edit- right 13v is ok for battery at rest and around 14v ish when engine is running -Your onboard charger should be good -just takes a little longer to charge a bigger battery-only works on hook up -
    Your solar could possibly be feeding back to the fridge relay causing probs if you understand what I mean ?Bear in mind as I said before it only works on 12v off engine/alternator-Chances are you will have a twin/dual relay allowing engine to charge leisure battery as well as fridge.If it is pulling from the L/B when engine is not running you will soon kill the batt so get it rewired
     
    Last edited: Mar 25, 2012
  3. kickstart

    kickstart Funster

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    When its warm and in southern/France/Spain we always find it coldest and best to run on gas,never had any probs,but on 12v it never keeps cold enough.:RollEyes:
     
  4. TheBig1

    TheBig1 Funster Life Member

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    1 its not your battery and 12.8 volts no load is typical. It only goes above this when a charge is being applied to the battery. below this shows a discharged bettery

    2. This sounds spot on and I would go so far as to say your 12v heating element is faulty and drawing too much current being almost short circuit when warm. Will then cycle on and off as it heats up and cools down

    3 the charger is irrelevant as the 12v only opperates when the engine is running by design. The alternator must be working if the battery is not going flat after starting the engine a few times. power for the 12v opperation is from the vehicle battery not leisure battery
     
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  5. magicsurfbus

    magicsurfbus Funster

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    Thanks for the suggestions so far folks.

    I should clarify that the fridge simply will not run on 12v if the engine is off, even if the solar panel is belting out its full voltage/ampage into the leisure battery. The solar panel's charge controller cuts off below 14v, whereas the alternator puts at least 14v into the circuit. There's no way the fridge is going to drain the leisure battery and it never has in the past. Whether the control panel simply detects any current of 14v or over, or whether it specifically detects ignition and alternator I don't know.

    As a sideline, one potential drain on the leisure battery in our van is if the blown air heating fan is left on by accident - this is not controlled by the control panel and appears to be connected direct to the leisure battery. I have recently had an isolator switch fitted to the leisure battery for when it's in storage, just as a precaution. Worth noting that one though.

    The multimeter reading on the engine battery at rest is about 12.8v so based on answers so far that seems to rule out a battery problem. The voltage in the circuit when the engine's running is around 14v, falling rapidly away to 12v and a bit when the fridge is switched onto 12v.

    I'm inclining towards the fridge fault suggestion outlined by TheBig1 at present. Whether that can be fixed before next Friday is another question..
     
  6. pappajohn

    pappajohn Funster Life Member

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    The fridge will only operate on 12v when the engine is running, and (typically) is linked to a control panel that monitors engine and leisure battery state. When I start the engine and monitor the voltage in the circuit there is a clear increase in voltage as the battery charger starts up. However, when the fridge is switched to 12v there is a steady drain on the voltage until it drops below the level where the control panel cuts off the fridge in order to preserve engine battery voltage. The fridge then repeatedly switches on and off as the voltage fluctuates around this cut off point.

    firstly, we need to know what type of fridge is fitted ?
    is it a 3 way 12v/230v/gas or is it just 12v ?


    just 12v is a compressor fridge, it wont work on gas or 230v......12v/230v/gas is an absorption fridge.
    without going back through the posts i think you said it works ok on gas and 230v so its an absorption fridge !

    your onboard battery charger serve no function whatsoever whether the engine is running or not, unless its plugged in to 230v hookup.
    it only works on 230v.
    the engines charging system supplies the 12v power to the fridge and charges the leisure battery when 'on the move'

    the fridge should be wired directly to the engine battery via a fuse and an alternator sensing relay, a device which can tell when the engine is running and switches on the fridge 12v supply.....

    typically the fridge will draw around 10amps on 12v from the engine battery when the engine is running...which is why it doesnt run all the time on 12v as your 80amp battery would only last around 3 or 4hrs with the engine turned off.
    turn off the engine and you also turn off the fridge 12v supply and it must then be run on gas or mains.

    after all that.....it sounds like the fridge heating coil has a fault and as it gets hot (sounds odd but thats how it works) it is failing and stops working, then as it cools it 'repairs' itself temporarily until it gets hot again...time and time again.





    note to self...read all the posts....sorry TB1
     
  7. DP_JAY

    DP_JAY Funster Life Member

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    The fault is either the fridge 12v heater circuit is drawing too much (should be about 10A) or the alternator is not putting out enough.
     
  8. Wildman

    Wildman Read Only Funster

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    The installation is not designed to run a fridge on 12v when the engine is off. End of story.
     
  9. DP_JAY

    DP_JAY Funster Life Member

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    I think you may have missed this

    "When I start the engine and monitor the voltage in the circuit there is a clear increase in voltage as the battery charger starts up. However, when the fridge is switched to 12v there is a steady drain on the voltage until it drops below the level where the control panel cuts off the fridge in order to preserve engine battery voltage. The fridge then repeatedly switches on and off as the voltage fluctuates around this cut off point"

    12v heater circuit or charging circuit/alternator fault.
     
  10. TheBig1

    TheBig1 Funster Life Member

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    If it was an alternator fault, the problem would exist when the fridge was off as well, so not charge the vehicle battery. That is why I believe it is a fridge specific fault. Even the wiring before the fridge sounds to be ok, as the relay will still energise when the alternator is pushing out its voltage. If the wiring or relay were faulty, again this would show with the fridge being off.

    It really is as simple as a 12v heating element being faulty when hot causing the voltage to cycle.:thumb:


    like this one
    http://www.ebay.co.uk/itm/Thetford-...ervan_Caravan_Accessories&hash=item588fec22b6
     
  11. DP_JAY

    DP_JAY Funster Life Member

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    I agree, the most likely/obvious thing is the a fault on the the 12v fridge circuit/heater element, but it is also possible that the in/out "cycling" is caused by LOW alternator output/faulty relay/bad connection.
     
  12. aba

    aba

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    just as a tester to all the above pointing to a fault with the fridge.

    start the engine turn on the cab heater fan to full and switch all headlamps on then check the battery, if the voltage stays at around 14 volts then its not your alternator. which points to fridge being the problem.

    however if the voltage drops to 12 again then it is a problem with your alternator.

    any half decent auto electrician will be able to test the alternator
     
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  13. magicsurfbus

    magicsurfbus Funster

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    Thanks for that tip aba, I'll give it a go.

    Also - apologies to others for the confusion caused by my equating 'alternator' with 'charger'. It should have read 'alternator'. The charger is largely irrelevant in this case as we rarely (if ever) hook up to a 230v supply.

    No chance of the fridge's 12v circuit being fixed before we travel now, so we'll use a 12v cool box for the essentials en route then switch the fridge to gas on arrival. No major bother (apart from the additional cost of the cool box).

    Advice appreciated as always folks - well worth the annual £10 membership fee.
     
  14. pappajohn

    pappajohn Funster Life Member

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    once your fridge is down to temp on gas it will retain the temp for quite a few hours if the door isnt opened.

    cool it down on gas or mains at home then start it again on gas at your destination.

    cuts out the cost of crappy coolboxes which, unless you spend some serious money, will never get quite cold enough.
     
  15. magicsurfbus

    magicsurfbus Funster

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    As a follow up to this thread, this long-running problem has now been sorted.

    On investigation by (yet) another servicing company it was found that the Earth connection from the cab battery had deteriorated to the point where it was messing with the fuseboard's ability to monitor the engine battery state. Consequently the fuseboard was denying 12v current to the fridge and leisure battery in a mistaken effort to prioritise the engine battery and preserve its charge.

    I've had to fork out around £200 for a new fuseboard, and the the Earth connection has been fixed. All is now as it should be. I plan to send the old fuseboard back to its makers in Italy for a diagnostic check and an estimate for repair, and if the estimate is reasonable I might have the job done so I have a spare one. It's only a matter of time before the item becomes obsolete, and the new one took ages to get hold of.
     
  16. Microchip

    Microchip Funster

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    First find where the volts are dropped, this could be heat on certain components as the fridge is drawing approx 10 amps...= 120watt heating element.
    Check the relay contacts as they may be carbonised also burnt feed wires etc..
    careful use of a multimeter should find the fault fairly easy by measureing across these components....:thumb:

    Keith
     
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