My main concern was that 100A draw along with killing the diodes at the generator as to what the voltage drop across the entire electrical system actually is. The generator is only rated at 90A and, remembering that this supplies the entire vehicle, not just the fan that's pulling 100A which is 10A beyond capacity as it is.

The other factors such as thermal dissipation factors and such, I'm not worried about that and, as with 6 AWG, it is a non issue. But, the other components in the vehicle may be not only affected by EMI / RFI.

At the time of voltage being applied TO the motor, the stall current is going to be a major issue. When the motor is started, if the rotor speed is zero, the induced EMF in the rotor can be huge. As a result, very high current flows through the rotor. This is reminiscent to a tranny where, the secondary is shorted, thus causing the primary to draw tons of high current from the mains thus, a voltage drop of unknown proportions is seen across the board - including at the PCM.

Just what the recovery time from this level of voltage drop is unknown across the system but, it is very hard on the generator in general. What will happen is, it's going to exceed the generator output thus, drawing down the battery as the fan is cycled on and off. Depending on the frequency of those cycles and just what the stall current actually is, those diodes are not going to tolerate that heat for too long before going south.

I am in agreement with every aspect of this discussion that is presented here.

CM

 

The alternator's magnetics shouldn't be able to make enough current to let the magic smoke out of the rectifier. If the magnetics can, then perhaps sacrificing the fan motor by using smaller wire to feed it is in order... or a radical rethink of the whole darn thing is.

The alternator should never see that peak (inrush) current. The internal resistance (source impedance) of the battery is a helluva lot lower than that of the alternator so the battery will provide almost all of the inrush current. The alternator's going to carry fan full load current, battery recharge current, and just a smidgen of the inrush current, but it's a system designed to replenish the battery over years and years of starter operation so it's up to that task and then some.

The alternator, serpentine belt, and battery will all see reduced operational lifetimes but barring the presence of other high loads in the system it will be perceptible but not alarming.

Food for thought: The Perma-Cool Cool-Pack draws just 21A at full load, right around half that of the junkyard fan. So it presents about half the load to the alternator that the junkyard fan does, and will have half of the inrush current as well. My back of the envelope calculations indicate that it's going to cost right around 3/4 horsepower to drive the Cool-Pack, and twice that for the junkyard fan. If the purpose of the electric fan is to free up power for moving the vehicle and/or increasing fuel economy, why spend 3/4 horsepower more and accept accelerated wear in the affected parts (alternator, battery, serpentine belt) to drive the junkyard part that offers no engine cooling efficiency increase at all?

The Cool-Pack costs more up front, but other than that the junkyard part has nothing but down sides to it.

 

The only way around this would be one of two things:

1. The use of a startup resistor acting as a current limiter or

2. The omission or replacement of the Lincoln fan altogether.

I recommend the later of the two.

CM

 

www.dccontrol.com

Very high quality fan controllers. Lots of different options and they give you a lot of info about the parts you are buying. If my flexalite controller ever bites the dust I'll replace it with one of these.

Spal also makes a pretty good controller, but I don't think they have as many options as DCC.

 

wow guys, lol