DeWitts dual fan module

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Sep 28, 2010 | 09:00 PM

tjwong

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From: Portland Oregon

DeWitts dual fan module

Anyone using the DeWitts replacement dual fan module? If so what was done to run the fans? I was told to just connect the power leads to the existing fan controller but I am unsure if that would work seeing how the OE fan was made to run at variable speeds from the variable speed controller that is controlled by the PCM.

Sep 28, 2010 | 10:00 PM

cencalc6

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From: Fresno Ca

I'm also looking into this mod.

Quote:

Originally Posted by Tom DeWitt

It is a dual fan, flat paddles, and almost double the factory cfm at 2760. Keep in mind, this is only designed to fit our Direct Fit radiator.

We now have a wiring schematic that allows you to run the fans directly from the ECM and no aftermarket switch. Since the factory fan plug will not handle the amperage, you will have to cut it off and splice wires. The fan utilize two heavy duty relays (included) to introduce the power to the fans, so aftermarket wire harnesses are still necessary.

http://www.dewitts.com/pages/product...asp?ProdID=427

Last edited by cencalc6; Sep 28, 2010 at 10:10 PM.

Sep 28, 2010 | 11:04 PM

tjwong

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From: Portland Oregon

Quote:

Originally Posted by cencalc6

I'm also looking into this mod.

I was told to connect both of the DeWitts fan motors to the existing fan motor controller. But what worries me that having two motors will increase the current load by a considerable amount. I have already heard of fan controllers going bad just because the PCM calibration was set so that the stock fan comes on early and runs longer. There has been a few cases of the fan controller failing which causes oveheating. So I am hesitant about connecting additional load to the controller. I have years of experience with large AC Drives in the pulp and paper industry and connecting more current load than the drive can handle is a no no. If those fans motors are atypical fan motors they can have as much as 40 amps of in rush current and 20+ while running at full speed. Plus the OE motors are a PWM device, and I am not so sure that the DeWitts motors are rated for this type of duty.

Sep 28, 2010 | 11:55 PM

cencalc6

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From: Fresno Ca

Quote:

Originally Posted by tjwong

I was told to connect both of the DeWitts fan motors to the existing fan motor controller.But what worries me that having two motors will increase the current load by a considerable amount. I have already heard of fan controllers going bad just because the PCM calibration was set so that the stock fan comes on early and runs longer. There has been a few cases of the fan controller failing which causes oveheating. So I am hesitant about connecting additional load to the controller. I have years of experience with large AC Drives in the pulp and paper industry and connecting more current load than the drive can handle is a no no. If those fans motors are atypical fan motors they can have as much as 40 amps of in rush current and 20+ while running at full speed. Plus the OE motors are a PWM device, and I am not so sure that the DeWitts motors are rated for this type of duty.

Here's a pic of my old 93 Mazda RX-7 powered by a LS2... I ran a dual SPAL fan setup and it was troublefree kept my car under 190's in 100+ degree HEAT....2 signal wires Hi and Low from the PCM/ECU to a couple relays,12V switched power Straight from the Battery and 30amp fuses Did the trick.I might give this a try and hopefully I dont screw something up

Sep 29, 2010 | 01:06 AM

tjwong

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From: Portland Oregon

Quote:

Originally Posted by cencalc6

That is a nice clean setup. Which ECM are you using to control the engine? I could wire the dual fan system to the E38's discrete outputs but I don't have the time as the customer is from out of my area and I have limited time to install the upgraded radiator and the dual fan kit. It can be done, but I need the pins to wire the relays into the PCM harness and time which unfortunately I have neither. The same E38 PCM also controls engines in GM trucks, and in the trucks they use discrete control of the two fans via relays. All one needs to do is to reconfigure the fan control tables in the engine cal and wire in the relays to the correct termination points in the PCM connector.

Sep 29, 2010 | 02:40 AM

cencalc6

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From: Fresno Ca

On the RX-7 I was using a E40 PCM 24X reluctor wheel.I Do have the pinouts for that.But unfortunately I'm having trouble looking for my E38 pinouts.... I need look in the morning and see what I have. I did a quick search and I found somebody saying that on X1 connector (Grey connector on the PCM) that pinout 58= Low speed and 17= High speed but I'm not sure.

Sep 29, 2010 | 08:46 PM

0Tom@Dewitt

Former Vendor

Joined: Jan 2000

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From: Brighton

Quote:

Originally Posted by tjwong

We recommend getting two relay/harnesses.

http://www.dewitts.com/pages/product...asp?ProdID=255

This provides you with full power to the fans and each one is independantly protected with a 30amp fuse. You can then use the sensor wire from the old fan plug to signal the relays on/off in pwm mode. I have a schematic at work and I'll get it uploaded to our website tomorrow.