Just read the post today about electric fans & the alternator. I didn't get the answer I wanted.... I just installed an electric fan-wired it directly to the positive on the battery- to an in-line fuse-to a switch on my dash (Ground is good) so I can run it without the car on. When I hit the switch - the in-line fuse blows (15amp). How many amps should it draw?What gauge wire & what gauge switch do I need to make it work? I am using 14 gauge right now. I guess it draws more amps than what I figured. ......67 Chevelle 396
Thanks

Should be on the fan motor somewhere. The surge when first turned on can be double the running current. Try a 30 amp slow blow fuse. Switch needs to be a good 30 amp as well or it will burn out quickly.

Should be on the fan motor somewhere. The surge when first turned on can be double the running current. Try a 30 amp slow blow fuse. Switch needs to be a good 30 amp as well or it will burn out quickly.

I agree... This is a good place to also run a relay. That way the switch is ONLY switching the relay, and most relays handle 30+ Amps...

They start out relatively inexpensive... $6 and up from Summit, but you might even find something at your local autoparts store, etc...

http://www.summitracing.com/parts/PCO-5591PT/

Just read the post today about electric fans & the alternator. I didn't get the answer I wanted.... I just installed an electric fan-wired it directly to the positive on the battery- to an in-line fuse-to a switch on my dash (Ground is good) so I can run it without the car on. When I hit the switch - the in-line fuse blows (15amp). How many amps should it draw?What gauge wire & what gauge switch do I need to make it work? I am using 14 gauge right now. I guess it draws more amps than what I figured. ......67 Chevelle 396
Thanks

You are very likely VERY low as far as the capability of that fuse to handle the startup load of the fan(s). Also you really need to research the way that fan is wired to the battery. While what you have done will work it is not optimal for the charging system. Last but not least did you uprate your alternator and charging system wiring?

Depending on the alternator you have and the requirements of the fan(s) you might have a situation where the fans are drawing juice from the battery whenever they are running. If the alternator cannot keep up with the steady state amperage requirements of the fans and other accessories you will be running the battery in a constant discharge condition whenever the fans are on. Sooner or later that will lead to grief. You need to know what it takes to start those fans AND what it takes to run them. You also need some idea what the rest of the car is drawing and what the alternaor is capable of delivering.

If the total, worst case, amperage requirement of the car is > than what the alternator can supply you are gonna be draining the battery while running the car. I don't think I need to tell ya what that will eventually lead to. Another factor here is what is the output of the alternator at low engine RPM. In town the fans are gonna be running, in town the engine is at low RPM. If the alternator is not delivering a healthy charge at low engine RPM (even if it has sufficient charging power at higher PRM) you will STILL be discharging your battery as you roll along on cruise night.

The older alternators don't put out their max output until they are operating at moderate levels of engine RPM. Later models like the CS series are belting out max or near max output at lower engine RPM than the older alternators found on these cars. Consider an alternator upgrade to the CS or later series alternators.

Doug, I'd highly recommend using a minimum of 30A relay. Your 14 gauge wire is good for toggling the relay. I'd run 10 gauge for the main power and ground path for the fans. Also, most switches cannot handle much current, I'd replace it when you wire up the relays.

Need to give us the specs on your fans to figure out the current draw. Startup on large fans can be as high as 100 Amps (Lincoln Mk VII) but run on about 30-35, others are less.