want a fridge in my truck

Hi everyone,

Just wondering if anyone can help me.  Having thought about some options (Thermoelectric cooling, 12volt compressor fridge) and ruled them out, I am resigned to simply using ice packs in my coolbox style insulated container.  

However, I have done some experiments, and, find that from start up at say 35 degrees C, putting several ice packs (filling up about 10% of the space) takes around three hours to get the space cooled to even 12 degreesC.  At this point the packs are softening but still virtually frozen.  My objective is to get the cooled space down to temperature quicker (I know putting pre-cooled food/drink in will help).  In other words, I want the ice packs to give up and exchange their energy faster.  The way to do this is by making an enclosure to fit inside the 'fridge' to house the ice packs, complete with an air outlet, and a 12v fan to circulate through.  Typically a small computer fan is pretty much ideal except that it runs too fast. 

I read the post and replies to the guy wanting to reduce the speed of his fuel pump, and noted that Pulse width modulation was the way forward.  Does this still apply to my idea, even though there is hardly any load on my little motor?  Also, can anyone give me a diagram, or suggest an adaption to provide a 12v timer (to operate a relay).  Timer might be the usual (domestic) adjustable range of 1 or 2 periods on/off throughout the day?

ps. Any tips on building the enclosure mentioned above would help too.

Thanks guys.   PS, buying bits is not so easy in Cyprus, we don't have Tandy, RS or Maplin. 

Here is something to consider. Get a powered insulated cooler of some sort (like a larger car fridge) and make it waterproof on the inside (if it isn't already done). Get your food and drinks in there and keep the food in waterproof containers. Then put water, ice and salt into the container as well. This should get your food to about 4-6 degrees C within a few minutes (less than 10 minutes by my calculations) and then maintained for several hours by the powered cooler (I'm estimating around 6-8 hours depending on ambient temperatures... or at least that is what my thermal calculations say) 4-6 hours for unpowered coolers

But if you cannot introduce water, consider getting a hold of a motorcycle AC unit (found on higher model cruiser bikes) and have it retrofitted into the truck. Lots of fabrication work here, but I know it will work. The small confines of the cooler will make the AC system hit it hard and maintain the cold temperatures. (Most bike systems should get it to at least 10-13 degrees C in a couple of minutes)

Ganbatte ne!