11 May 2011

Auxiliary Fans

For those of us who drive our classics regularly, reliability means more than just starting easily and stopping well. One major part of this reliability is a robust cooling system. The good news is that for many cars, just having things right will keep temperatures where they need to be. However, there are times when adding an electric fan may help keep the system cool under pressure.

Before deciding your car needs an electric fan, you may want to do some basic troubleshooting. If you suspect problems, first determine is whether your car is truly overheating, or just running hot. Our definition of overheating is when the cooling system boils over or the temperature of the coolant goes above 240 degrees F.  You should be concerned if temperatures frequently go over 200 on the street (race cars are a different story), but worrying every time the gauge goes above 180 isn’t worth it.

Here are some steps to ensure the fan will solve a problem and not  just treating symptoms caused by another problem.  First, check that there are no leaks in the system and that it is full of the proper coolant mixture. Next, make sure that the radiator has a uniform distribution of heat. This can done by moving a hand (or better yet, an infrared thermometer) slowly across the front of the radiator at a safe distance so as not to be burned or caught in any moving parts. If there are spots more than about 10-15 degrees cooler than other spots, it's probably time for a radiator repair or a new unit. Then, ensure the thermostat is working as expected (again, an infrared thermometer helps) and the proper cap is on the system. After these cooling system tests are done, look at the tuning of the engine. A poor state of tune can affect operating temperatures. Overly retarded or advanced timing may be the culprit, as can improper carburetor mixtures or stuck chokes.

If the car is still running hot or actually overheating, the last consideration is what conditions cause the problem. If the engine is hot when the car isn't moving very fast (or standing), it's likely a fan-related airflow issue. If the car is hot at speed, it still may be an airflow issue, but another fan may not solve it — it could be that ducting needs to be changed on the inlet side or that the air cannot adequately exit. 

One last factor for decision making may be packaging on a modified car. If an engine-driven fan just won't fit, an electric is the only choice.

When buying an electric fan, find the largest and most powerful unit from a reputable source. There are a lot of cheap units available that just won't move enough air to make them worthwhile. 

Mounting an electric fan is usually straightforward. If possible, it should mount behind the radiator instead of in front so it blocks less incoming airflow. Most fans come with a tie-wrap mounting system, threading the ties through the radiator fins. More sophisticated metal mounts can be fabricated or sometimes purchased as well. Most fans also use a thermostatically controlled switch to run the fan only when it’s needed.

Wiring the fan is as important as mounting it. Be sure to follow the manufacturer’s recommendations and have wiring and switching that can handle the amperage requirements of the fan. Failure to properly wire the fan so may not only result in overheating, but an electrical fire.

Hopefully, these tips will give you the information you need to keep your classic’s temperature where you can stop worrying about overheating and enjoy the ride.

Resources:

Spal USA
Fan manufacturer
www.spalusa.com
(800) 345-0327

Flex-a-lite
Fan manufacturer
www.flex-a-lite.com
866-447-5967

Summit Racing
Fan kits from many manufacturers
www.summitracing.com
800.230.3030

Speedway Motors
Fan kits from many manufacturers
www.speedwaymotors.com
800.979.0122

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