Current Draw For Cooling Fan

[blazingspider]

I have the original cooling fan set up in my 77 spider. Does anybody know how many amps the stock cooling fan draws when running? Can you get a brush kit for these anywhere?

The reason why I ask is that when the fan comes on when I'm stopped at a traffic light, the idle speed drops significantly to the point where if I don't keep my foot on the gas pedal the motor will die. FYI...I've got the 65 amp bosch alternator in this car and the charging system seems to be operating normally.

Thx,

Blaze

[klweimer]

Not sure, but I bet it's more than 10 amps anyway. You might want to check the voltage on your battery with the fan on and off. Unplug and plug the connector to the fan, check the fan ground, etc. If I had doubts about my fan, I would probably trade it in on one of the larger, more efficient modern fans our vendors sell. I also don't think I've seen brushes for sale for these motors.
Kirk

[aj81spider]

I only have the manual for a 1976, so you should check your owner's manual. However the 76 manual has only two things on that fuse, the fan and the horns. The fuse is a 25 amp fuse. I'm guessing the horns only take 5-10 amps, so that would leave something between 15-20 for the fan for max draw. Continuous draw is probably less than that.

[So Cal Mark]

the electrical load causes the alternator to put out more amperage, thus a heavier load and idle speed will drop. The initial surge when a fan starts can hit 30amps but that should be momentary. Many newer cars ramp up fan speed slowly so you don't have that initial amp surge, but that requires a module type fan controller

[spider2081]

It has been a while since I bench tested a bout 5 fans after replacing the bearing and cleaning them up. I believe it drew 12 amps running with the fan blade on, at 13.75 volts measured at the fan connector. The start-up current is much higher as stated but that surge is very short time duration. I am pretty sure the fuse in the later cars is a 16 amp fuse and that is for the horns and the engine cooling fan. I have not tried blowing the horn and have the fan come on. I have tried blowing the horn while the fan is running and the 16 amp fuse does not blow.

[blazingspider]

Thx for the replies!! The fuse for the fan / horn never blows and it's rated at 16 amps so I know the draw is under that value. Perhaps the bearings are shot and the brushes are worn enough to get the operating current draw higher than it should be but still under the fuse rating.

I bought one of those aftermarket cooling fans from a neighborhood auto parts store once and it crapped out after maybe a month so I'm hesitant to try another one.

[TimpanogosSlim]

Aftermarket fans don't have a good reputation in general.

In racing, fan upgrades are often OE fans from other vehicles.

I'm interested in finding a common junkyard fan that will work for our cars - but radiator geometry is a lot different these days, and fans are frequently mounted to a shroud in a way that is not easy to adapt to another radiator.

Earlier this year i saw a pair of Denso branded fans in the trunk of a Kia in a junkyard that mounted to a flat plane (tabs on the outer edges rather than the shroud bolting to the motor), and I'm kinda kicking myself for not taking notes on the part numbers. Since they were in the trunk, they probably weren't taken off that car.

Vick offers a 12" fan and used to offer a 14" fan - the 14 is probably as big as we can realistically install and might not fit on cars with automatic transmissions due to the hard lines for the transmission cooler in the bottom tank.

I have no experience with Vick's aftermarket fans.

[spider2081]

I'm interested in finding a common junkyard fan that will work for our cars - but radiator geometry is a lot different these days, and fans are frequently mounted to a shroud in a way that is not easy to adapt to another radiator.

I have taken apart a number of the stock Fiat fans and they are built very well. The motor brushes don't show signs of much wear and the commutators are not grooved. The main problem is the shaft bearing eventually wears out. The metal casting rolls over the bearing preventing it from coming out. I grind the roll off with a die-grinder and sanding disk. to remove the bearing. The bearing is a standard size with the size written in the bearing seal. To hold the new bearing in I drill and tap the housing for 2/56 screws and the head of the screws hold the bearing in place. Hardest part is getting the plastic fan blades off the shaft with out damaging the blades