How are you wiring your dual electric radiator fans? Without external fan controllers, using LS PCM

How are you guys wiring your dual electric radiator fans?
My LS PCM from PSI conversions apparently has low speed and high speed fan control wires, which I believe provide a ground to pin 86 on the fan relays.
I bought the 98-04 Dodge Intrepid radiator fans, which has both fans wired together through a harness. Should I cut off the harness and wire each fan independently to their own relays that each get their own signal? I want the high speed fan to only turn on when called on by the PCM.

For each fan, they would get their own relay:
Pin 86 - PCM ground signal
Pin 85 - Ignition?
Pin 87 - to Fan power
Pin 30 - constant power, fused 40A to battery

Does the above seem correct?

383_StealthRam said:

It depends what you prefer...

You can wire dual fans so lo speed means one fan on, second fan off and when hi speed is commanded by PCM the second fan then comes on. Two relays, each controls one fan, they both are either on or off full speed.

Or you can wire the fans in series/parallel so they BOTH run at half speed (splitting voltage) in lo speed mode, then when PCM commands high speed they both jump to full speed. This requires three relays in order to switch the fans wiring from series to parallel circuit for the lo/hi speed respectfully.

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I am leaning towards wiring it as in your video with the 3 relays - I just do not understand which of the leads on the intrepid 4 pin fan to feed into. There is a red wire, a blue wire, a black wire and another red wire. Each motor has 3 wires - red, blue and black.

81cutlass said:

Does your intrepid fan have relays on the fan or not? There is a standard and HD cooling option.

The fans are 2 coil so if you power 1 coil both fans turn on low and power coil 1 and 2 they turn on high.

My intrepid fans have 2 wires, a black, yellow, and green. I have 1 relay triggered with the low speed fan signal from the LS ECU to the yellow wire for low speed and a second relay connected to the green wire for high speed that is connected to the high speed fan command from the LS ECU. I left the OEM harness on the intrepid fan and put a 3 pin weather pack connector from the fan to the chassis, so if I want to pull the fan/rads I don't need to pull off any wiring. The OEM intrepid fan has a connector that I didn't have a mate for so I just replaced the connector with one I had on hand.

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No relays on the intrepid fan, its a standard fan I picked up off of ebay.

However it sounds like yours has 3 pins on the main harness? Black (ground), Yellow (low speed) and Green (high speed)? Is that correct?

My intrepid main harness has 4 pins - red, blue, black and red. Each motor has 3 wires - red, blue and black. I am assuming that red and blue are the two hots, and the black is the ground, but what would the second red be for?

383_StealthRam said:

It depends what you prefer...

You can wire dual fans so lo speed means one fan on, second fan off and when hi speed is commanded by PCM the second fan then comes on. Two relays, each controls one fan, they both are either on or off full speed.

Or you can wire the fans in series/parallel so they BOTH run at half speed (splitting voltage) in lo speed mode, then when PCM commands high speed they both jump to full speed. This requires three relays in order to switch the fans wiring from series to parallel circuit for the lo/hi speed respectfully.

Click to expand...

After testing the fans for continuity from the 4 pin harness, I believe I determined the following:

Red supplies power to both fans

Blue also supplies power to both fans

Black ground only goes to the driver side fan (fan #1)

Red / Black ground only goes to the passenger side fan (Fan #2) but it reads 8 ohms (??) at fan #1 red...

I am going to use a low speed/temp relay to power the blue supply and a high speed/temp relay to power the red wires. I am going to tie both grounds together (Black which is ground to fan #1 and red/black which is ground to fan #2).

Since the red and the blue feed both fans, my assumption is that with the two relay setup, both fans will run at low speed with the first relay on, and then when high temp kicks on the second relay, both fans will get the second windings powered up giving high speed to both fans.


Relay # 1:

Pin 86 - PCM ground signal for low temp (195 F set by PSI conversions on the PCM)
Pin 85 - Ignition 12V (10A fused fused to ignition)
Pin 87 - to Fan power - blue wire on fan
Pin 30 - Battery 12V (40A fused to battery)


Relay # 2:

Pin 86 - PCM ground signal for high temp (205 F set by PSI conversions on the PCM)
Pin 85 - Ignition 12V (10A fused fused to ignition)
Pin 87 - to Fan power - red wire on fan
Pin 30 - Battery 12V (40A fused to battery)

383_StealthRam said:

I'm not an expert (with hands on for) the Intrepid fans wiring, but from what I've researched on your behalf what you've outlined appears correct.

Basically the four wires at the connector, two are the individual fan motor grounds (Black and Red w/ Black), the BLUE is the LOW speed coil of both fans, and the RED is the HIGH speed coil of both fans.

Only thing I'm not sure about is if you need to turn OFF Relay #1 when your turn ON Relay #2 or if it doesn't matter that they are both (the blue and the red wires) powered at the same time.

I'm guessing it doesn't matter and it actually requires both the RED and BLUE wires to both be powered for FULL speed, and when only the BLUE is powered you get low speed but I would double check by mocking it up and testing it.

HTH

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I agree with all of what you are saying.
I do not know if both windings need to be energized at the same time to get full speed, or if its either one OR the other. Also I am unsure if the PCM will send BOTH the low and high speed signal during high speed.