i installed an electric fan with the thermostat on my cutty, and i need help on finding a ignition controlled power source. i tapped into my electric fuel pump,but that is a constant 12v source and it runs constantly. any suggestion. mike

 

That does not sound right. Your fuel pump should not be running all the time, only during ignition. Unless there are two sources for the pump, one being constant 12 volts (higher amperage from a relay) and the other being ignition (to actually activate the pump) and when both occur the pump runs, but still......that just doesn't sound right. Also, if the fan is triggered through a thermostat the fan wouldn't run constantly unless the engine was really hot when you installed it and by saying constantly you meant for as long as you had it on and the engine had not cooled down yet so you shut it off. Where is your thermostat? are you using a relay? Was this a kit and did it have directions? Some people use ignition from the distributor.

 

You need to wire the electric fan so it runs for a time after you shut off the engine. That is how I've always seen electric fans wired.

 

@ oldsguy the fuel pump only runs during ignition but there is two sources. the fan came with kit my thermostat is located by the inlet hose. i would like for the fan to come on only when needed and not run constantly and tapping in to the fuel pump allows the fan to run constantly because it also has the 12v source. is there a particular wire coming from the distributor that i could use. mike

 

well I don't know about that,Unless your speaking of people installing that them self's an doing it that way.Any new car with an electric fan only comes on when the car is on or when the key is in ac position....or I can be wrong

 

My wife's 2003 VW Beetle will run the fan for about 5 minutes once you shut the car off and the engine is particularly hot. I believe the 93 Buick LeSaber I had did the same thing. I though it was standard fare for electric fans. If it isn't then it wouldn't be that hard to do if you have a temperature switch and 12V hot wired to the fan.

 

Hi there, most new vehicles actually have an electronic controller box and two thermo switchs to control the fans. They can run up to 15 min. after the car is shut off. Anyway, what you need is thermo switch that switches to ground when it reaches a certain temp. You also need a relay. Find a power wire that is switched (usually there is a switched terminal in the cabin fuse panel) This wire should go to the control side of the relay. Ground the other side anywhere. Next, run a wire from a fused constant power source to the switched side of the relay. After that, run a wire from the ground side of relay to the thermo switch. The thermo switch should be a one wire switch, install it on the intake or radiator. I hope this helps.

 

This is true, but the fan doesn't always run after the ignition is shut off. It's just possible that it could, depending on conditions.

In fact, if you look carefully around the fan area in most any car with an electric fan made in the last decade or so, there will be a warning sticker stating that the fan could turn on at any time, not just when the ignition is in the on position or the engine is running.

 

Why would the fan run after the eng is turned off?The coolant is no longer cirulating unless you have an electric water pump I don't see the point of it.As for wiring why not run constant live [fused ] wire to fan and run the fan ground to to the temp sender,the sender should be marker n/o normaly open ,if it has 2 wire terminals run ground from fan to one terminal and run a wire from other terminal to a good ground,if it has 1 terminal then it is grounded through the sender.when coolant reachs temp that the sender is rated at, the sender will close making a path to ground and the fan will come on.I say run the ground to the sender because if the wire was to rub on anything and short out it would just cause the fan to come on and not burn anything and it is much easier to secure the live wire going to the fan,it don't move like your eng does.Also if you use constanst power the fan will stay on untill on coolant cools and the sender opens ,removing the path to ground, if you want the fan to turn off when ignitoin is off then take the power from a ignition source.If you have A/C then then you must take the a/c fan enable ground wire and connect it to the sender terminal with the ground coming from the fan.

 

It's a good question, but there must be a reason as the auto manufacturers wouldn't design such a system if there wasn't a purpose.

The moment the engine switched off is when it is the hottest as it is still at operating temperature but the coolant is no longer circulating. This has always been true, not just with more modern cars. The residual heat raises the engine's temperature above normal operating temperature. By having the fan turn on or stay on for a few minutes after it is switched off, the engine is cooled a little more quickly, even though the cooling is just from blowing air over it.