Only Getting 5 Volts To The Fridge While Driving...

[Wyaye wires]

When the fridge is switched to automatic I am getting an alarm from it. On checking the wiring at the back of the fridge it's only showing 5 volts.
I know I should check the wiring from the battery through to the fridge and determine where the voltage is going, but could it be the engine battery starting to fail that is the cause?

I switched on the ignition the other day, without starting it immediately, within ten seconds I got a battery low voltage alarm.

As an electrical numpty any help appreciated thanks.

 

[ES Cumbrian]

Does the engine start?

 

[pappajohn]

The fridge shouldnt recieve any volts from the engine battery until the engine is started.

Assuming it is started and still only 5v i suspect a faulty fridge relay.....dirty or badly burnt contacts.

If your starter battery was only 5v under load it isnt failing....its already failed big time.

 

[Wyaye wires]

Does the engine start?

Yes.

 

[Wyaye wires]

The fridge shouldnt recieve any volts from the engine battery until the engine is started.

Assuming it is started and still only 5v i suspect a faulty fridge relay.....dirty or badly burnt contacts.

If your starter battery was only 5v under load it isnt failing....its already failed big time.

Thanks PJ,

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[scotjimland]

or there is an earth on the 12v fridge element .. it may have 'blown'

disconnect supply to fridge and re measure the voltage when the engine is running

 

[ES Cumbrian]

I suspect that the fridge relay contacts have become damaged and are now high resistance and its dropping the voltage, of course anything else in the circuit that's high resistance would also cause this. I always go for a "moving" contact first then explore more if that fails to cure it.

 

[ES Cumbrian]

Dont forget that measuring the voltage with the load removed with a digital voltmeter may give a misleading reading as there will not be any voltage drop through a high resistance contact. Using a 12volt bulb to test with removes this problem as a current will flow and show any fault in the circuit.

 

[Wyaye wires]

Thank you to everyone who replied...

I will report back if and when I solve problem...

 

[ES Cumbrian]

In an ideal situation you would disconnect your fridge at the rear then connect a new element and switch on. Measure the voltage at the element terminals and see what you get. Measure the engine battery voltage. If the element terminals goes down to 5 volts and the engine stays at over 12 volts you have a problem with either the relay or the wiring. If the volts at the new element stays around the same as the engine battery and the element gets hot your old element is faulty. Now you will not have a spare element but rigging up a 12volt headlight bulb will draw current and you can then do the above measurements and know where the fault is..

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[Jaws]

Thank you to everyone who replied...

I will report back if and when I solve problem...

At least the bloody thing does not flop outside the van at random moments !! LOL !!