my fridge on 12 volts

[scottbott]

many moons ago my fridge light came on when driving on 12 volts,as it was supposed to do but I replaced a few things such as indicator arm,ignition switch and one day my wife noticed that the light was not on,if I put my lights on the fridge light lit up,I have been living with this but it has been bugging me.today I was looking at the fridge relay(for another reason) and was just checking the colour of the wires on it and suddenly wondered about the two red wires on pins number 87 and 30,could these be the wrong way around??,I did have the relay out and disconnected years ago and was thinking maybe I put them back wrong,was not sure what would happen if I swapped them around to check this out,would it be ok to try?

[CJH]

I doubt that's your problem. If you look at the diagram for the split charger system in the wiki (which will be the same for the fridge - just replace the Leisure Battery in that diagram with your fridge), you'll see that the relay is switched by the circuit across pins 85 and 86 (thin wires, 86 is probably connected to your blue alternator wire, 85 to earth, or vice versa), but all that the relay does is join 87 to 30. The diagram shows 30 connected to the starter battery and 87 to the Leisure Battery (or your fridge), but the circuit would work if they were switched over (although that's not the case if your fridge relay is also your split charge relay, so check whether that's the case).



My guess is that something's wrong with the switching circuit (pins 85 and 86). With a meter you should be able to confirm that one is connected to earth all the time, and the other is dead until the engine's running and then provides 12VDC. If the relay only works when you switch the lights on this could be an earth problem I guess - it depends how the earth is routed from the relay (pin 85 in the above figure). So maybe with your meter, once you know whether it's 85 or 86 that is the earth, you could check the resistance to earth, and see if that's high initially, reducing when the lights come on.

I would expect the battery feed (pin 30 in the diagram) to be on it's own fused supply, but I suppose that may not be the case, and maybe you've affected that supply. Again - easy to check with a meter - either pin 30 or pin 87 should be live all the time... hmm, maybe not I suppose, since it could have been wired with an ignition controlled live, in which case it should be live with the key in the first accessory position without the engine running.

[scottbott]

thanks for the reply,I have the Autosleeper "basic wiring diagram" in my hands at the moment and it shows that the wire from pin 85 goes to the vans ignition switch,which was replaced about three years ago but they are only a plug and play type of thing,pin 86 is for the earth

[CJH]

OK, so you should be able to run the fridge with the ignition key in the accessory position, without the engine running. Not quite as 'safe' (from the point of view of flattening your battery) as using the alternator blue wire, but unlikely to be a problem unless you deliberately run the fridge with the key in and without the engine running.

Anyway, if that's the case, I can't explain what might have gone wrong. But it should be easy enough to check with a meter:
- Pin 85 should be dead with the ignition off, and live (battery voltage) with it on. If turning the lights on affects the operation, that'll be a clue.
- Pin 86 should have very low resistance to earth. Again, if turning the lights on affects the resistance, that's a clue.
- Either Pin 30 or Pin 87 should have battery voltage at all times, even without the ignition on (but check the wiring diagram in case that feed also comes from an ignition controlled live).
- The other pin (87 or 30) should go to the fridge, but that's not so easy to check with a meter unless you can get to the wiring at the back.

[CJH]

Are we looking at this diagram?



The feed to pin 30 doesn't appear to be ignition controlled, so should be live all the time. My money's on pin 85 (the feed from the ignition switch) being the culprit. See if you can find that at the switch, and make sure it's not wired in such a way that it's only live when the lights are on.

[scottbott]

yes that is the diagram I have I will have a look at the weekend,thanks for the reply

[scottbott]

I had a poke around today and found these things,the red cable with the black tracer from the ignition switch has been cut and a thin black wire has been added to it,do not know who,the black cable with the yellow tracer has got hot at some time and has melted the plastic housing,I have a spare of this,who sells cable like this I have looked at the people I buy my electrical bits from but they do not stock these colour cables,both are 4.0 cable,I will replace the red/black cable completely from switch to fuse box and probably do the same with the black/yellow