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Keep Cool During Surveillance

Whenever you have to have extended surveillance in one spot, you may have a need to cool your vehicle without running the engine.  I know all about hot cars in South Texas.   They can become ovens.  A relatively inexpensive way you can keep your car cool, is to make your own Cooler-Top.   There are commercial alternatives out there, but making your own Cooler-Top is relatively easy and inexpensive.

The advantage to making your own Cooler-Top is you can modify this easily to fit whatever ice chest you may already have.  I had an old one that I have had for probably more than 25 years.  Ice chests that the lid can be removed can be used in more different places than one with a hinged lid – but either will work.  Sometimes it just becomes a pain keeping the lid propped open.

What you will need:
Some Insulation Foam Board (it is lightweight, insulated and easy to cut)

An Ice Chest 
A 12 V Fan (Radio Shack 273-238 – Low amp draw  $19.99)
Cigarette Lighter Plug (Radio Shack 270-049 3 Meter cord $9.99)
4 x 1¾” 8x32 screws with nuts and lock washers (to attach the fan)
If you plan on running this a long time, and some extra fans – you may want to add an extra marine battery and battery box (This would cost more than all of the other parts together above).

I recommend that you have the following tools:

Tape Measure
A sharp knife or drywall saw
A soldering Gun (not necessary, but makes better connections)
Pencil/pen (something to mark with)


Open the ice chest and measure the inside of the chest just above the lip (if it has one) You will need to cut a piece of the foam board to snugly fit in there.  If there is a lip, cut a second piece of the foam board to snugly fit (not so snug you have to fight to get it in and out).  After the two pieces are cut, carefully glue them together.   Check the fit in the ice chest before going any further.


Next, you need to cut a 4.5” Square Hole 2” from one end.  You can just trace the fan.  This will be for the fan.  Center the hole from side to side.  This is a hole for the fan.  If you use a different sized fan, you will need a different sized hole.   On the opposite end of the foam board, cut a 1.5” Hole 2” from the end.  This is the exhaust.  You can put a 1.5” PVC 90 degree Elbow in here if you wish to direct the airflow a certain direction.

Attach the wires from the cigarette lighter plug to the fan.  You need to do this first to know which way the fan blows air.  You can solder the wires or use small wire nuts to attach the wires.  Plug in the lighter plug to test the fan.  Be sure to note which way the fan blows.  Put the fan into the larger hole.  I used "plumbers tape" at the corners to help hold the fan in place.  You want to attach the fan where it blows down into the ice chest.  This is very important, as pushing air is easier than pulling air.

Once you attach the fan – the Cooler top is ready to go.  Just put Ice in the Ice chest, put the cooler-top in place and plug in the cigarette lighter plug.  After a few seconds cool air should be flowing out of the smaller hole.  

To keep humidity lower – use frozen water bottles of keep the ice in the ice bag.  This should give you air about 50 degrees or so – It will not cool down a really hot car very well, but if the vehicle was already cool from running the A/C before turning it off, it should be able to keep it quite nice for several hours.

The fan only draws about 0.3 amps so you can run it a while without draining your car battery.  To run it even longer, you can attach a separate battery so your car battery isn’t too low to start your car when you need to tail the subject in question.  How long it cools depends on how much ice, type of ice (cube or block and of course the ambient temperature.

I tried this out for 3 hours in my driveway.  I had sunscreens in the windshield and it was 98 degrees according to my Suburban’s thermometer.  After 3 hours, the car was cooler inside than the outside.  This is not normal without the use of the Cooler-Top.  I didn't have a way to measure the temperature inside, but I would guess around 82ish.  Not that great, but definitely bearable.  The Suburban had no problem starting.  A few operational points to make:

The system works better (cooler air) with bag ice out of the bag and the cooler being nearly full.  This causes more surface area of ice for the cooling of the air.  I think I will do this with possibly some frozen water bottles thrown in so I can drink the water when needed.

I had fun with this project – spent just over $30 including the small bag of Ice at Bucees.   I think it is a viable solution.  What is even more funny, after I started this project I found that you can buy something like this ready-made for $40.  It works with specific ice chests, and they will sell you a foam ice chest that works with it .  So make your own, or buy one.  I recommend using this for those long hot surveillance jobs.  I get nothing from the company that makes them.

Whatever you do, stay safe!

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