Cooling fan start current

[Bitsyncmaster]

I've already got what I was looking for (the start current and timing) so I'm doing some other testing just for curiosity.

I've got one of my original fans and another OEM shroud. So I tested that current both without it mounted to the OEM radiator and with.

12.0 volt = 10.5 amps without and 12.4 amps with
12.5 volt = 11.3 amps without and 13.2 amps with
13.0 volt = 12.0 amps without and 14.0 amps with
13.5 volt = 12.7 amps without and 14.8 amps with

I suspect the high currents of OEM used fans is due to brush dust conducting current to adjacent armature coils. So I'm going to try to open this fan motor up and clean it and then retest the currents. I think I need to pull the fan blade off to open the motor and not sure if that will happen without damage. That is why I'm using this OEM fan since I want to keep the other two fans untouched.

[novadmc]

I've already got what I was looking for (the start current and timing) so I'm doing some other testing just for curiosity.

I've got one of my original fans and another OEM shroud. So I tested that current both without it mounted to the OEM radiator and with.

12.0 volt = 10.5 amps without and 12.4 amps with
12.5 volt = 11.3 amps without and 13.2 amps with
13.0 volt = 12.0 amps without and 14.0 amps with
13.5 volt = 12.7 amps without and 14.8 amps with

I suspect the high currents of OEM used fans is due to brush dust conducting current to adjacent armature coils. So I'm going to try to open this fan motor up and clean it and then retest the currents. I think I need to pull the fan blade off to open the motor and not sure if that will happen without damage. That is why I'm using this OEM fan since I want to keep the other two fans untouched.

if you ever need another pair of OEM fans for testing, for extra data-point collection or anything, let me know. Mine are just sitting in a box on a shelf in my garage. their exterior housing is all beat up and paint flaking, but they ran just fine when i pulled them to replace them with Toby's units.

[Bitsyncmaster]

if you ever need another pair of OEM fans for testing, for extra data-point collection or anything, let me know. Mine are just sitting in a box on a shelf in my garage. their exterior housing is all beat up and paint flaking, but they ran just fine when i pulled them to replace them with Toby's units.

Thanks but I think we all know the OEM fans seem to increase there current draw as they age. I did some testing reading CFM and RPM but that was back on the old .com forum. CFM testing is pretty hard to get a standard results since the sensor (i have a hot wire anemometer) measurement position is critical. CFM testing would need to be done with side by side fan testing to just get a comparison of air flows.

What it all boils down to is does your engine stay cool and the AC pressures don't run to high. Now to do it with less current draw helps the electrical system.

[David T]

Thanks but I think we all know the OEM fans seem to increase there current draw as they age. I did some testing reading CFM and RPM but that was back on the old .com forum. CFM testing is pretty hard to get a standard results since the sensor (i have a hot wire anemometer) measurement position is critical. CFM testing would need to be done with side by side fan testing to just get a comparison of air flows.

What it all boils down to is does your engine stay cool and the AC pressures don't run to high. Now to do it with less current draw helps the electrical system.

It isn't that simple. The thermostat controls the temperature of the motor. Once the car is moving, air is rammed into the intake so you don't need the fans over a certain speed. They will be running anyway if the A/C is on but their current demand will be less because of the ram air. I agree measuring CFM can be tricky which is why you must set parameters for the testing. If current demand is dropping and you achieve the same or better cooling effect then implicitly you must be moving more air. Maybe a more reliable indicator would be to read head pressure in the A/C system for comparison purposes. If you are moving more air (and transferring more heat) the head pressures should be correspondingly lower. As for the OEM motors drawing more current as they age, I suspect that is a very small change, the only things that will change are the bearings may lack enough lubrication and the brushes will be worn. Unless windings are shorting the current draw should not change that much over the lifetime of the motor.

[Bitsyncmaster]

Well I lucked out that the two bolts holding motor together are rusted so I could remove the two nuts on the end of the motor without pull the fan blade off.

There was about 5 of the commutator spaces that had brush dust on one end. I blew it out but had to use a pick to get those out.

Now the test still mounted on the radiator.

12 volt = 13.2 amps
12.5 volt = 14.0 amps
13.0 volts = 14.8 amps
13.5 volts = 15.6 amps

What the hell......the currents increased 0.8 amps higher. Maybe the RPM is higher now but I really expected currents to drop.

I wonder if the permanent magnets lost some magnetism if the current would increase or decrease. I would guess you would loose RPM and the currents would fall.