Last year, I posted a thread (https://www.ford-trucks.com/forums/1...-question.html) discussing my installation of a dual electric fan setup using a Dorman 620131 fan (originally OEM for the 1999-2003 Ford Windstar) in my E350 with the 460 carbureted engine. I went into some detail about the adaptation, the airflow offered by the setup (4500 cfm), modifications of the stock shroud to give the best utilization of the fan capability and finally, a discussion of fan controllers. I concluded a solid state pulse width modulated (PWM) controller maximized the benefits of the electric fan swap. Everything was completed in late November, the snows hit and the E350 motorhome went into storage for the winter.

In late April/ early May, I awakened the beast and decided to clean up several engine compartment details. To my surprise, after about 30 to 40 minutes of driving, the engine began to overheat. Closer inspection showed the battery to be dead! I recharged, checked the gauges and found that when the PWM temperature controller came on, the alternator switched off. The fans draw between 12 and 38 amps depending on fan speed, and when the alternator switches off, the fans are just running off the battery. In a very limited time, in this situation, the battery is discharged below 10 volts and all systems are off!

Careful testing showed that when the PWM function of the controller was operating, alternator output was zero. When PWM was not operating, the alternator was functioning perfectly. My choice of controller has a fail safe mode wherein you can flip a switch and the controller will apply full power to the fans with no pulse control involved. Using the fail-safe switch I was able to quickly switch between PWM on and off. Experiments showed that I could switch the alternator on and off easily and repeatedly.

The alternator manufacturer insisted I had mis-wired the alternator and something other than PWM generated interference was the cause. The controller manufacturer immediately concluded that this was a case of Electro Magnetic Interference (EMI) due to the rapid pulse switching of the fan currents (12-38 amps) at KHz rates. His solution was to shield the cables going to the fans from the controller and to add some capacitive filters.

This controller actually switches the ground lines for the fans on and off to control speed and applies full 12-14V to the positive terminal of the battery. So, I proceeded to shield the ground wires from the controller to the individual fans by wrapping with copper foil shielding tape with a conductive adhesive. After wrapping the ground wires, I connected one side of each shield to chassis ground (one end of a shield only) and added an electrolytic capacitor pair (100 uf and 1000 uf) to the positive terminal at the fan with the other side of the capacitor connected to chassis ground. As a result, the problem disappeared! The alternator functioned perfectly and the PWM fan controller varied the fan speed from about 5% of full speed to full speed as demanded by the radiator temperature.

So, to conclude, variable speed solid state PWM controllers operating electric fans can generate strong enough electric (EMI) fields to literally turn off the voltage regulator in your alternator. Shielding and careful wire placement is the solution!

 

Use a slow startup setup with it, the quick load is an issue I've been told.

 

Slow start-up is a characteristic of the controller I'm using, but as soon as PWM spikes started (as seen by the oscilloscope), the alternator shut down. There are several papers in the technical Electrical Engineering literature that suggest that there are components in the voltage regulator that shut down in the presence of high EMI fields. In aly case, after the shielding and capacitor addition, the controller shows the slow startup that adds life to components.Slow startup is critical for but difficult to achieve in relay based controllers. In that case, relays are often fried by quick loads. In the case of solid state controllers, very high current capacity solid state relays are needed.

 

I put a G3 alt in my 73 E100, later had issues with my battery, found the 2 gauge wire that ran to my wheelchair lift had fallen on my exhaust, welding itself to it, I haven't a clue how my alternator survived, but I do have issues with it eating belts during engagement, perhaps you could upgrade alternators, isn't yours the G2?

 

I had a surge years ago, was on a GM vehicle, tracing the alternator charge wire, had melted and ground on the block, only did it on occasion so the shop that was to test it found nothing, refused to do it while there.

 

We had a wheelchair lift installed in an older Nissan Quest. Had to go to 00 AWG welding cable to minimize the voltage drop with the high current. The welding cable insulation really softened with its underfloor location and the exhaust heat. Finally, I sheathed the cable with exhaust heat shield sleeve. Worked well enough then!

Actually, I have the 3G (or G3) version for better cooling and higher output. My alternator is the Powermaster 47759 which is an 3G rated at 200 amps. They tell you (various alternator manufacturers) that you should never turn the alternator on and off while the engine is running. They cite unspecified internal damage. Well, turning on and off is exactly what I was doing while trying to figure this problem out. During my experiments, I probably turned the unit on and off at least 60 times. Yet, with other alternator tests, there is no evidence of any damage. I'll carry a spare voltage regulator just in case!

Your suggestion of switching from the G2 to the G3 is a very good one. Many engine fires have been triggered by poor design aspects of the G2, and the upgrade gives better alternator cooling as well - which is very important for component longevity in the E350 engine compartment!

 

Powermaster was convinced the problem was in the exciter circuit (charge wire) but I could find nothing wrong there. Monitored the exciter wire current and voltage and all were in specs. The exciter current was 6.68 ma. and voltage was 9.3 V whenever the alternator was running and functioning correctly. When the engine was stopped, key on the current was 27.88 ma. and this was exactly the same value when the engine was running but the PWM pulser was operating before shielding. After shielding, engine running, the exciter current was steady at 6.68 ma. and voltage at 9.3 V. This was the case for alternator current output from 12 A to 78 A at engine RPM of 1,100.

 

BTW my 3G came as a one wire, when having my battery issues, to get parts stores to bench test my alternator, I had to swap the regulator to the standard type used on Ford cars, from what I've been told, when I got frustrated with it squealing the belt, causing me to upgrade the pulleys, to run dual belts on it, tough to get the pulleys for my van, there is a delay start regulator so it has no load startup, I think the one wire had a delay, I don't have it now.

 

Is yours on factory wiring, I ran my charge output 2 gauge straight to battery, even put a 2 gauge ground on it, has been suggested on some forum to ground the alternator bracket.

 

Fascinating story! Thanks for the update.

 

maples01, my wiring is the same as yours! 2 AWG to the battery from alternator, 2 AWG ground from alternator case to frame ground and same gauge to engine block ground. The belt squeal problem with high output alternators and v-belts caused me to switch the v-belt drive to the Ford Poly-Vee serpentine belt setup from the 460 EFI engines of 88-94. Had to swap out pulleys, brackets and AC compressor. Used parts from a 94 E350. No belt squeal, better AC compressor and very clean engine compartment!

 

The 73 has a 3 bolt pulley on the crank, it is a nightmare for finding parts, I wasn't happy with choices, the 2 belt crank pulley was billet aluminum, quite expensive, I did want serpentine but it was too much, having no other accessories, the one for the water pump, to keep it turning the right way, outrageous. Did you see how many different serpentine arrangements there are, more ribs, wonder if it's wider. So does your alternator have a delayed regulator?

 

Yes, the aftermarket serpentine conversions are quite pricey! That's why I went OEM Ford Poly-Vee. The junkyard parts came to $80 including the pulleys and the special alternator/smog pump bracket as well as the bracket for the AC and power steering pump. The Ford "serpentine" system uses two belts and the water pump turns in the same direction as the v-belt water pump. Works perfectly, but you do have to replace the AC compressor. I switched to a Sanden.

As far as I know, my alternator does not have a delayed start regulator. The slow start feature is implemented in my setup by the PWM fan controller.