Fridge not running on 12volt (1 Viewer)

RobGriff

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Aug 2, 2010
240
208
TONYPANDY Rhondda Wales
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Hi my fridge will not work on 12volt only makes a buzzing noise. Runs great on 240 and gas any idea’ s please thanks Robert
 

MikeD

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Dec 21, 2011
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As above. 12v usually only works with the engine running

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pappajohn

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Aug 26, 2007
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Engine running and fridge will not work only a buzzing noise from fridge
How do you know it's not working.
In 12v operation there is very little heat from the vent, if any, and no noise at all.
12v will not cool the fridge, it will only maintain a temperature already present from gas or 230v.
 
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RobGriff

RobGriff

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Aug 2, 2010
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TONYPANDY Rhondda Wales
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Fridge works well on other services 240/gas but will not work on 12v when engine is running

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Jan 28, 2008
10,104
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Dovercourt, Harwich, UK
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7 years campers before that
you need to find out if theres a 12v supply to the fridge when the engine is running if theres not it could be the relay
 
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RobGriff

RobGriff

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Aug 2, 2010
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Hi Steve thought it might be the relay ,going to have a look tomorrow after work . Hope you and Diane are keeping well . Rob and Deb
 
Nov 7, 2015
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since 2015 previously caravaning 25 years
Can't help with the noise but when our Thetford fridge stopped working on 12 volts it was due to a bad electrical connection at the plug and socket found at the rear of the fridge at floor level in our case easily accessible from the lower vent cover, pull the connector apart and look for a burnt connection.

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Jan 28, 2008
10,104
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Dovercourt, Harwich, UK
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actually the buzzing does point towards a relay not holding follow the buzzing noise to locate it mine is behind the fridge
 
Dec 12, 2010
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I've just recently deleted the couple of pics on my phone that I took of the 12 volt electrical connections on the rear of my Dometic and I seem to remember seeing an automotive relay in amongst it all. If that's playing up, it will make a buzzing noise. Usual reasons for it to buzz are low voltage supply to the coil or a bad connection. I've had to replace a couple of corroded Lucar connectors on mine.
 
Apr 27, 2016
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There are two 12V supplies to the fridge. One is a low-current supply to power the control board. The other is a high-current supply (about 14 amps) that powers the heater element that works the cooling.

The low-current one is on all the time. The high-current one is selected by the manual or auto selection. On most British MHs you can not run on 12 volts unless the engine is running, and this is done using a relay.

Has this problem suddenly started after working OK for some time? I ask this because if it's always been like this, or the wiring has been changed or is incorrect, the relay could be wired wrong, so that it switches itself on and off rapidly, making a loud buzzing sound.

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Taff Thomas

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Apr 7, 2018
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Don't own one yet
Funnily enough I have this problem on the motorhome I have just bought (second hand.) I will post more detail when I pick it up.
 

Gladys

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Jul 29, 2018
2
0
Funster No
55,233
We have had our second hand Motorhome for the last 2 and a half years and the fridge has always worked fine whilst we’re travelling on 12v. But the last 2 times we switched over to 12v when setting off, the fridge has made a really bad noise. If we turn it off, the noise stops. Can’t understand why suddenly it has started this really bad noise
 

pappajohn

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Aug 26, 2007
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Can you elaborate on a 'really bad noise'

By the way, you only get 5 free posts then to continue you must subscribe.

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Gladys

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Jul 29, 2018
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Hi pappajohn

It’s like a really high pitched screech. It doesn’t make the noise on electric or gas mode, only after we have have switched it to 12v. Pretty sure the noise starts when we start the engine when it’s in 12v mode.

Thanks for your reply.
 

oppy

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Nov 8, 2014
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56
Glossop, North Derbyshire
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Coach built Lunar
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At the FFF meet last weekend we had an expert tell us that the fridge would not work on 12v (whilst the engine was running) because the relay was faulty. I found the relay, or rather two relays jammed behind the battery. I now have them in front of me, one is a Hella rated at 20/30V and the other is a Tyco but with no rating on it. Both are 5 pin and both have the same numbers allocated to the pins. So, do you think that both are related to the fridge? Can anyone help this poor numpty ?

Peter

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pappajohn

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Aug 26, 2007
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Since 2005
At the FFF meet last weekend we had an expert tell us that the fridge would not work on 12v (whilst the engine was running) because the relay was faulty. I found the relay, or rather two relays jammed behind the battery. I now have them in front of me, one is a Hella rated at 20/30V and the other is a Tyco but with no rating on it. Both are 5 pin and both have the same numbers allocated to the pins. So, do you think that both are related to the fridge? Can anyone help this poor numpty ?

Peter
No, one is the fridge, one is the split charge to the leisure battery.
Which one is which can only be determined by tracing the wires or using a multimeter.
 

pappajohn

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Aug 26, 2007
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Since 2005
Hi pappajohn

It’s like a really high pitched screech. It doesn’t make the noise on electric or gas mode, only after we have have switched it to 12v. Pretty sure the noise starts when we start the engine when it’s in 12v mode.

Thanks for your reply.
Sorry Gladys, that's beat me.
Only thing I can think will make a high pitch screech is a slack/worn fan belt under load.
Can't think of anything fridge related.... There are no moving parts on the 12v side of the fridge.
 

oppy

Free Member
Nov 8, 2014
87
56
Glossop, North Derbyshire
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Coach built Lunar
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No, one is the fridge, one is the split charge to the leisure battery.
Which one is which can only be determined by tracing the wires or using a multimeter.
Thanks young fella. I pulled them both out and took them to the dreaded Glossop Caravans and asked the electrician about them, he said that they were both the same, so for £3.50 each I have replaced them both and now have a working fridge. So many thanks

Peter

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pappajohn

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Aug 26, 2007
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Sorry Peter, should have said they are both the same.... 30amp automotive relays as fitted to millions of cars, vans and trucks.
Only difference being where the output goes... Fridge or battery
 

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