12v Fridge with ignition

[Ant-t]

My kitchen refurbishment is nearly completed and I want to connect my 3 way fridge to the 12v ignition feed. All wiring is in place but a po had disconnected it at some point. The fridge works on 12v and the ignition feed is good with the engine running. I have an illuminated rocker switch that I want to wire in to give the option to use the fridge or not on journeys but I have no instructions on how to install the switch. Does anyone have any pointers on installing this switch? All input appreciated.

[Mark S]

If I understand the question, you have got a supply for the fridge that is live with 12V when the engine is running (and presumably is dead the rest of the time). This implies that there is a relay upstream activated by the field signal from the alternator, closing the relay when the engine runs. You want to put a switch in series between the load output of this relay and the fridge itself to give an extra manual level of control. This will enable you to turn off the fridge when the engine is running (but not to turn it on when the engine is not running).

I would suggest finding the relay and putting your switch into the control circuit of that rather than directly in the line to the fridge, otherwise you will need a hefty switch to handle the current. This allows the relay to continue the job for which it was designed: switching current to the fridge. The relay is probably located in the sink console close to the fridge.

I imagine your load passes through pins 87 and 30 on the relay and pins 85 & 86 are the control circuit to close it. One of these is probably earthed to ground (brown wire) and the other goes to the alternator line. I would tend to splice my switch into the alternator line, earthing the indicator lamp to the low (ground) side of the coil. If you put the switch solely into the ground side, the switch would work but the illumination would not.

A bit of play with a test bulb/voltmeter under conditions of engine on and off should help you work out what's what.

[Oldiebut goodie]

Hasn't the fridge got an on/off switch already? Sledgehammer to crack a nut scenario springs to mind.

[Ant-t]

Good input, thank you, yes your summary is correct. I'll trace the wiring and find the relay, the original setup was removed before i bought my van so I've nothing to go on. I found the 12v ignition feed with my multimeter and I found the fridge 12v wire once I had removed the fridge. There is no 12v on/off switch on the fridge only gas controls.

[bigherb]

Autohomes didn't use a relay, the fridge power was switched on directly by the ignition switch to a DIN socket in the cupboard next to the fridge which you plugged the fridge into when you wanted it powered. You can substitute a switch instead of the plug and socket and it would be better to fit a relay also.
RM122 fridges are not fitted with a switch hence the inline plug and socket.

[Jeff J]

Autosleeper did fit a relay which is itself switched. While it gives different options it also gives more potential for faults. Personally I have only had the switch that controls the water pump fail, this is not via a relay, so probably proves the value of having one.

[Mocki]

Simply put ,switch the trigger wire , not the high amperage output

[Ant-t]

I'm going to have do some research on switches and relays, thanks for the input all