# 12 volt fans on fridge wiring



## gm6vxb (Nov 3, 2007)

Looking at fitting some cooling fans to the Thetford N180 fridge to assist cooling in really warm weather.
Rather than just wire direct to 12 volts, does anyone know if there is a supply that only switches on when the fridge is switched on, i.e a 12 volt output from the fridge when on with gas, mains or 12 volts.
I have not looked into it yet as busy doing other things.

Martin, GM6VXB


----------



## trevorf (May 16, 2005)

Possibly, but you may have to take the fridge apart and tap into the control PCB - not recommended.
It is usual to wire in a 12V computer fan via a separate switch for manual control. You only need to switch it on when the external temperature is above about 28degC ie during the hottest part of the day in summer.
You can also buy fan units that automatically switch on at about 28degC then off again when cooler. I think they are about £30.

Trevor

edit - found one here at £23.57, switches at 30C

fridge fan click here


----------



## PeterandLinda (Feb 21, 2009)

Hi

We have two fans fitted by Dave Newall and they have the option of thermostatic control or manual and they are fed from the 12v supply on the back of the fridge.

P&L


----------



## pippin (Nov 15, 2007)

I investigated the exact same thing a while ago.

There is a mass of unidentified white wires between the rear of the fridge and the front control panel.

I chickened out of trying to identify a switched 12V control line.

I tapped into the constant 12V supply and built a little thermostat control so the fans come on only when it is really hot at the rear of the fridge.

Do remember not to place the sensor anywhere near the hot flue gas output end.


----------



## gm6vxb (Nov 3, 2007)

Thanks both for replies.
In between rain showers I have had a look at wiring to the fridge. There is a supply that switches on from the main 12 volt supply, and of course the feed when the engine is running. I was hoping to find a supply that switched when the fridge power switch was turned on, but that looks like major surgery on the control panel which I am not going to do.
So plan is to wire up the fans with both a temperature controlled switch and temperature sensor so the fans will run slow if the temperature is not too high, and run full on if the temperature goes above a pre determined level. All off below (maybe) 20 degree, so mimimal power drain. One less thing to remember to switch on or off. Will make something up myself to do this.
Not sure what the temperatures should be but would imagine a start off point around 25-30 degree should be about right. Looks like a bit of fun designing and building something to do the job !.
Thanks,
Martin, GM6VXB


----------



## emjaiuk (Jun 3, 2005)

I know very little about fridge operation, but the consistent 12v supply whether on gas or electric would be the interior light. Where the feed would be and whether or not it would have a low rated internal fuse I've no idea. Having said that instinct would tell me to pay the extra for a switched or temperature controlled supply, increased airflow at lower external temperatures MAy have an adverse effect. 

Malcolm


----------



## pippin (Nov 15, 2007)

Martin - I used one of these:

http://cpc.farnell.com/_/mk138/mk138-thermostat-mini-kit/dp/HK00813

I modified it because in the "off" state the relay is energised and thus takes current.

The fans are off far more than they are on.

I changed the driver transistor from NPN to PNP (or vice-versa) so that the relay was on when the fans needed to be on.

I may alter one of the resistors to widen the hysteresis curve.

I used two computer fans in series as they run much quieter, in fact the relay clicking on and off was obtrusive at night until I mounted the unit on some rubber grommets.


----------

