how should i hook up my e-fans?

[kewljay223]

this really isnt an electrical question which is why i posted here. thought id get better answers. i know how to wire up relays and size wires/fuses for the ckt.

my question is that i bought 2 16" fans. i made a "shroud", if you will, for them and thought of something today that now makes me wonder how to go about wiring them up. i did some research and it seems that STOCK TRUCK/CAR FANS have a low and high speed. the fans i bought are single speed. on the pcm, fan 1 out is for low speed when temp reaches 223* and fan 2 out is high speed when temp is at 230*

anyway, i have a few options id like to run by you guys. need help picking the best one..

1) i orginally planned on having one kick on from fan1 then the second from fan2 since they are single speed fans. but after thinking about it, there will now be a huge hole in the shroud (due to the second fan not being on). if i have it hooked up this way, will this tend to suck air from where the non running fan is rather than through the radiator? if so then this wouldnt be ideal when idling.

2) have both fans kick on from fan1 out and call it a day. with both on they should cool it down extremly fast. this means that they will both be kicking on and off constantly. will this will lessen the life of them quicker?

3) hook both fan1 and fan2 out in paralell using two relays. this would essentially be the same scenario as #2 since the temp will never be above 230* The reason for this is in case a fuse blows, relay dies, short ckt, etc. fan2 out would basically be a backup of fan1 out since it is 2 diff circuits. i would keep the circuits isolated also so a short on one wouldnt mess with the other.


i prefer option #1 as it would leave me a backup fan in case the first went down. but im thinking option #3 is what everyone is going to recomend.... sooooo, 1,2 or3???

[1lowzu]

F body E-fans or 05 up Silverado E-fans either set will work just fine and a Nelson Performance 3 relay E-fan harness its pretty much as plug and play as you can get and looks very nice under the hood

[kewljay223]

F body E-fans or 05 up Silverado E-fans either set will work just fine and a Nelson Performance 3 relay E-fan harness its pretty much as plug and play as you can get and looks very nice under the hood

i think you misunderstand. i already have 2 brand new fans and i made all the mounting braketry and a shroud for them. they will be installed tomorrow. i will be doing the wiring myself which i can do. im asking which one of the 3 options that i posted would work the best in order to controll them for the most effeciency/longevity? once thats established i will know what parts to get and how to hook up the wiring.

[bootlife]

I got my fans from Nelson, 1 fan runs on low with the AC, and when the truck gets warm the comp kicks them in to high, I havnt had any issues with only 1 running. You can fill it pulling air threw the grill. Hope this helps

[farmtruc]

low spped = configure the relays in series
high speed = configure the relays to switch in parallel

03+ pcm's are almost setup for the 2-pin pcm activation; just needs the calibration adjusted.
02 and earlier can use one pin or two pin but the a/c recirc door pcm pin must be removed and relocated(which is still why we offer the one pcm pin and a/c clutch activation harness)

fans must turn on when a/c is on also.

[kewljay223]

I got my fans from Nelson, 1 fan runs on low with the AC, and when the truck gets warm the comp kicks them in to high, I havnt had any issues with only 1 running. You can fill it pulling air threw the grill. Hope this helps

thank you. so your "low speed" output from pcm, aka fan1, only controls a single fan correct? and when it calls for "high speed" aka fan2, then your second fan will also kick on? As opposed to them both being on at half speed or high speed. and your saying it still draws air through the radiatior instead of the engine compartment from the hole of where the second fan is?

thats what i want to know. does anyone else have an aftermarket dual SINGLE SPEED fan setup where each fan kicks on seperately with no cooling issues? i dont have two speed fans. its either off or full rpm.

[farmtruc]

The stock fans aren't two speed either; they run on low speed thru relay configuration.
series then parallel.

the one fan on high speed will keep it cool as well, no issues. as long as they pull as much as the factory fans, since that's what we are basing it off.

[kewljay223]

The stock fans aren't two speed either; they run on low speed thru relay configuration.
series then parallel.

the one fan on high speed will keep it cool as well, no issues. as long as they pull as much as the factory fans, since that's what we are basing it off.

oh really? i was under the impression that they were two speed. ive never owned a gm vehicle that has had stock efans so i was basing my info from what i was getting from searching. and i came across the article below and others very similar for other gm vehicles/engines, so i assumed they were all basically the same... my opologies for assuming.

Cooling Fan Control 2.0L (LSJ)
The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood junction block. The ground path is provided at G105.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan s/p relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan s/p relay through the high speed cooling fan relay control circuit. This energizes the cooling fan s/p relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

The PCM commands Low Speed Fans ON under the following conditions:

• Engine coolant temperature (ECT) exceeds approximately 106°C (223°F).

• A/C refrigerant pressure exceeds 1 310 kPa (190 psi).

• After the vehicle is shut off, the ECT at key-off is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans ON under the following conditions:

• ECT reaches 110°C (230°F).

• A/C refrigerant pressure exceeds 1 655 kPa (240 psi).

• When certain DTCs set

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.



thats what i was basing my info off. anyway, i got my fans mounted today and hotwired one up to see what it would do with the other off. i put a rag and a piece of cardboard in front of the AC radiator and they sucked right up to it when the fan kicked on. so it seems that it will draw plenty of air through with one fan alone. so i will wire it up as a single fan normally and the second if necesary for higher temps etc. thanks for the replies. hers a few pics of my setup in case anyone is interested.

these are the 16" zirgo 2800cfm straight blade fans. they arent exactly super quiet but man do they flow!! plus it takes away that power hogging clutch fan and gives me room for intake piping...

[kewljay223]

just want to update in case anyone else wants to wire them up without buying a harness for them. i contacted zirgo to confirm that hooking them up in series is ok to do without hurting the motor of the fans as they will be only using half the voltage and they said it was ok to do. so i will be wiring them so they both kick on at low speed (series which=6v each) and both at high speed (parallel which =12v each) All you need is 1 SPDT an 2 SPST RELAYS. here is a diagram to hook it up with the exception of the pcm pinouts depending on what pcm you have. thanks for the input guys.