Fans draining battery w/ pettit fan switch
 

I have a Pettit fan switch, stock radiator, new oem thermostat. The fans cycle on and off as needed and stay on for some time after I shut off the car, probably for about 10 minutes. According to my VDO gauge the fans are coming on a little before 180 deg however I've asked Pettit and they say it's likely the gauge or the location of my temp probe (it's in the throttle body coolant line) that is not accurate. If I make a stop and shut off the car the fans stay on and I can barely start the car to leave. The fans tend to run on low constantly in the city. My battery is new and I re-charge every time I drive so it's ready next time. If I don't the car won't start or will barely start. Today when I had this problem I was not using the a/c or a/c fan, no lights, no radio, only a radar detector. It's 50 outside, not hot at all and I was driving fairly easy. Just little bursts through 1st and 2nd. It was nearly all city driving. I am sure if I was on a highway trip the fans would not run at all and I would not have this problem. It just seems strange because it's not hot outside.

My car does have the old school fan switch mod but I have not been using it since I installed the pettit switch.

Does the pettit switch cause the fans to stay on longer after shutdown? Anybody else have this problem? I'm thinking of getting an FC fan switch but I don't want to go to the trouble if it's not going to be any different. Does it sound like I have some other cooling problem or is this pretty normal?

when i installed my pettit fan switch it did cause my fans to stay on longer after shutdown and cause my battery to die. after i drove a couple thousand miles with it, the fans dont stay on as long. i figured since the switch is new its still pretty sensitive in your case? i got a new battery as well since my old one was bad.

It just seems like the fans run all the time during city driving. Maybe this is normal? I guess at 185 deg. it would be normal for the fans to run on low and maintain that temp. Maybe a radiator upgrade would keep the fans off a little more.

if you had a pfc, some one with a data loggit could of just lowered when the fans come on...

also how are your fans on after the car is off? i have to have the key on "on" position to have it run.

I thought it was normal for the fans to run for a bit with the car switched off. It may have something to do with the fan switch mod though although I have not been using the switch. Here is how to do it and what it does... http://www.fd3s.net/fan_mod.html

Do anyone elses fans run after you turn off the engine and remove the key? I can say that it does help cool off the engine bay.

Quick question, what battery are you running?

yes my fans to say on for a lil while after the engine is off. and i forgot to mention i have a koyo n flow on my car.

I called Cam when I was having this issue too. There are two jumper harnesses, one in the engine bay attached to the four relays under the hood on the passenger side, then another on the engine harness near the ECU. They are not necessary and can be removed to get your car running normal again without any ill effects. This is what was told to me by Cam and have had no problems since spring after I did this.

The fan mod switch (not the pettit switch) will kill your battery if not used properly. You must remember to turn off the switch when you leave the car. If you don't turn it off, it will continue to drain your battery until it is turned off ....... or until your battery is dead.

I have a new oem size battery from advance auto parts.

I have not been using the fan mod switch since I've installed the pettit fan switch. I literally don't flip the switch ever so it stays off all the time so I don't think the fan mod is causing any trouble.

Can you tell me in a little more detail what you did? When you say that you had no more problems, what was the difference? Did your fans not come on as early, runs as long, or not run after shutoff? I just want to know what to look for.