Fitting A Fridge Relay ?

Oct 1, 2013
6,029
9,827
Lanzarote
Funster No
28,377
MH
Conversion
Exp
2010
At the moment my Dometic fridge is wired straight to the vehicle battery as per the manual.

Unfortunately I can be a plonker sometimes and left the fridge on when the engine is stopped resulting in flat battery. The vehicle no starty. Boo !

So I wanna fit summat inline that will only let the fridge draw from vehicle battery when the engine is running.

Firstly what do I need ?

And is it a case of just fitting it to the postive wire from battery to fridge ?


Please keep answers simple as I am a numpty with leccy :mask:
 

DBK

Jan 9, 2013
13,644
22,475
Plympton, Devon
Funster No
24,219
MH
PVC, Murvi Morocco
Exp
2013
If you have a dashboard cigarette lighter check to see if it only works with the engine running - ours is like this. If it is this would be a better place to take the feed for the fridge from. Alternatively, use it to trigger a relay with the fridge wired to the battery through the relay.
 
OP
Yorick
Oct 1, 2013
6,029
9,827
Lanzarote
Funster No
28,377
MH
Conversion
Exp
2010
If you have a dashboard cigarette lighter check to see if it only works with the engine running - ours is like this. If it is this would be a better place to take the feed for the fridge from. .
The manual says it must be wired directly to battery.
Alternatively, use it to trigger a relay with the fridge wired to the battery through the relay.
What does that mean in simple terms ?::bigsmile:
 

DBK

Jan 9, 2013
13,644
22,475
Plympton, Devon
Funster No
24,219
MH
PVC, Murvi Morocco
Exp
2013
A relay is usually a coil of wire which when energised closes some contacts. Sometimes they also open contacts at the same time but that won't be needed in this case. A typical use of a relay is to use a small current to switch on something taking a higher current.

So the feed to your fridge would be connected to the relay contacts and the coil energised by a wire coming off somewhere where there is only a voltage when the engine is running.

The problem is finding a suitable relay and a socket to plug it into. Here is a possible one: http://www.halfords.com/motoring/garage-equipment/auto-electrical-supplies/halfords-hef555-relay-12v-40a-4-pin
If you look at the second image it shows which pins to use. 35 & 36 are the coil and the others the contacts. You would need to find a suitable socket although I guess you could use spade connectors. I would also add 10 amp fuses.
 

Saltings

Free Member
Sep 12, 2016
227
26
Buckinghamshire, U.K.
Funster No
45,087
MH
Chasson C626 Flash
Exp
since 2115
Hi

Have been in touch with Lenny re problem with running our Thetford 3000 fridge. It works on EHU and gas but no joy with 12V.

The PV cells do not seem to be charging the hab. battery either, although we are getting a current from them. Lenny writes:

"The solar not charging your batteries is probably due to the regulator being overloaded and shutting down.

The fridge not working on 12v could be the 12v element on the fridge blown should be easy to replace or a fault with the relay that feeds the fridge.

My problem is where is the 12v element in the fridge ("easy to replace??") - possibly in the enginwe compartment or in the electrics next to the charger? How do I know if there is a fault in the relay and how can this be replaced?

Cheers
Saltings
 
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