I plan on using electric fans with an LQ4 in my 86 monte. Jesse at Wait4mepeformance can turn on the fan controls in the ecm, and I've found a dual fan setup from a 97 intrepid. What else do I need for relays, fuses, wiring, etc.? Or do I simply attach wires from the fuse block to the fans?

 

What harness are you using?

 

I am also interested to use the PCM to control the electric fans. I have a LQ9 with the original Cadillac Escalade -02 harness. Is it simple to activate the PCM for this application, I have EFI Live Tune&Scan V2. M

 

I have a carb setup and have my fans wired to a switch currently, what are you guys using to turn your fans on without them hooked to the pcm?

 

Shawn, get one of these and use it to ground a relay at the preset temp.
http://store.summitracing.com/partde...5&autoview=sku

 

Wait4meperformance for both the harness and tune. Jesse is going to add wires for the electric fans, I assume from a vacant slot in the fuse block. He can also turn on the fan control in the ecm.

 

Anyone who knows which pin on the C1/C2 connector I should use for the relay to the electric fan ? Same as for the LS1 PCM ? Magnus

 

Hello to u all. It two ways you can fix this in a good way. The easiest way is to buy an external temp sens and a control box from Flex-a-lite or an equal producer. I did see a couple of different systems on Summit to. Check it out.
If you want to use the system in the ECU you must make your own system. The wire harness from the truck doesn’t support electric fans, but the ecu does. It must be enabled in the ecu first. Then you must make a small electric system from the ecu’s existing wire system with three external relle’s.
If you want I can post a drawing for it.
Reg Chris

 

And where would that install at? In the radiator or into the heater core lines or what? Also I'm not sure what you mean by the relay setup do you possibly have a diagram?

 

The wire that he is adding goes to the fan relay from the PCM to activate the reply. You will need a schematic for a F car or similar that uses electric fans to wire the rest of the relay. Not too tough to do and a lot cleaner than adding aftermarket sensors and stuff when you already have a computer to control the fans.

 

I would like to see how to do this with the pcm. I have a 99 truck pcm and harness.

 

I depends on what you are running for fans, I am running just one 16" fan so I did it with one relay. The PCM is the ground for the relay.
You need battery voltage to the relay with a 40 amp fused circuit
Battery voltage to relay with a 10 amp fused circuit
PCM ground from circuit for a 2002 F car is: C1 42 is low speed, C2 33 high speed.

From the manual:
The engine cooling fan system consists of two electrical cooling fans and three 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 fuse block. The ground path is provided at G106.

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 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 3 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 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.


LS1
The PCM commands low speed fans on under the following conditions:

• Engine coolant temperature exceeds approximately 108°C (226°F).

• When A/C is requested and the ambient temperature is greater than 10°C (50°F).

• A/C refrigerant pressure exceeds 1482 kPa (215 psi).

• After the vehicle is shut off if the engine coolant temperature at key-off is greater than 113°C (235°F) and system voltage is more than 12 volts. The fans will stay on for approximately 150 seconds.

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

• Engine coolant temperature reaches 112°C (234°F).

• A/C refrigerant pressure exceeds 1710 kPa (248 psi).

• When certain DTCs set.

Under normal operating conditions with A/C requested, the PCM will command the cooling fans on until vehicle speed exceeds 105 km/h (65 MPH).

 

Yeah, that unit is 3/8 NPT and won't fit into the LS head. Since it is 3/8 you might be able to turn it down and rethread it to M12x1.5. That thing should be capable of switching 30 amps so you wouldn't have to use a relay, although it would be a good idea. For 24 bucks and some 10 guage wire & fuse it would be the cheapest option by far.

Painless makes a fan controller with relay kit for the Gen III motors. About $80. They use to sell just the temp sensor for $39, but now they only sell the kit with relay and wires.

I bought an adjustable one that uses a wire stuck between the radiator fins. Wish I had got the thermal switch instead.

 

Hm i already have an autometer temp gauge in my driver side head. Im assuming id put that in my passenger side one? I think I'll just keep my manual fan switch. I ran them both through a 30amp toggle switch on 10 gauge house copper wiring which should be more than adequate for those fans. I ran my bat and alt wires in 0 gauge thhn copper too. I see lots of voltage everywhere with everything electrical.

 

Okej, I will go with the PCM solution instead of the external control. Since I have the truck harness I need to add new pin/pins in the C1/C2 connector, anyone knows were i can buy these pins? Thanks / M

 

You will probably be removing some emission related stuff like EGR, EVAP etc, just find the pin location in the PCM and remove it and put it into the pin location you need for the fans. Free fix and easy to do.

 

How do you change the pins in the two connectors? When I reworked my harness I just cut the wires at the connectors.. Does anyone have extra pins they can send me?

 

Thank you 69LT1Bird, I will remove some of the pin I wont need. I will make a new harness the forthcoming winter. I am still curious if anyone knows which pin on the C1/C2 connecter is dedicated for the fans since it is not marked on the electric scheme for the LQ9. M

 

I was told by my tuner that the truck PCM fan circuit operates a bit differently than the explanation given by 69LT1Bird. He mentioned something about it only having the ability to control a single fan.

Can anyone confirm if there is any truth to this.

 

Use the F car schematic above. I have a 2002 PCM and that is how I wired my fans.

For NoClassic, I looked at a couple of 2002 truck files from the HP tuners repository and can say that you have choices for the fans even on the trucks. No fans, 2 fans, or auxillary. You set on/off temps for one or two fans.