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No the main fan will not turn on until it is programmed by the tuner to do so. What I did was leave the mechanical fan on and ran all my wiring tucked it up zip tied it and drove to my tuner and when he did the program I just pulled the stock fan and shroud of and bolted up efan
Originally Posted by chardy909
can i drive my truck to tuner , after installing e-fans?
No the main fan will not turn on until it is programmed by the tuner to do so. What I did was leave the mechanical fan on and ran all my wiring tucked it up zip tied it and drove to my tuner and when he did the program I just pulled the stock fan and shroud of and bolted up efan
^^Thats what I would do as well. Get all the wiring in place and wired up but just zip tie the fan pigtails up out of the way until the Efans are actually bolted in. Also, I would go ahead and get the fan clutch broken loose unless you have recently removed it for something. It's a PITA to get it loose, so when you do finally get it loose, just snug it up until you get to to actually install the Efans. Just unbolt the fan clutch, a few 10mm bolts on the fan shroud, and then the Efans should slide right in. UNLESS you have the smaller radiator. If you have the smaller radiator, then you need to upgrade to the larger radiator prior to installing the electric fans.
If you have an 03-04 truck, then you will wire it exactly like this diagram shows. But on a 99-02, the PCM only has pin 42 available to use. The other trigger wire has to be connected to the AC compressor clutch relay wire. That wire is positive, so by me using an OEM harness, I had to add a relay to that wire to change it to a negative in order to trigger the fan relay pack, which is set up to be triggered by negative signals from the PCM. This extra relay is not needed if you use the pre-made harness from Blackbear. Thier harness is already setup to use a positive trigger from the AC wire. Now onto the wiring. First you want to remove your underhood fuse panel cover. Not just the lid, the entire cover. You will have to unbolt the corner fender brace in order to get it up and off. Now lift up the fuse junction block to get access to the underside. You will need to splice into the dark green AC clutch relay wire. This is the wire you need.
This is where you will tie in your relay (or trigger wire if using a Blackbear harness). The relay needs to be wired as follows:
Originally Posted by nonnieselman
Instead of useing the AC clutch to control the one speed, you can plug it into the PCM and the PCM controls both low, high, and AC on a 99-02 PCM.
Originally Posted by GMCtrk
Bumping this back up because I'm about to make the jump to OEM electric fans.
I just wanted to point out that the 99-02 PCM CAN solely control the electric fans.
I had LS1 efans several years ago on the 1 pin harness which utilized the A/C trigger wire for the second fan. This method is downright stupid, in my opinion and I wouldn't recommend it to anyone. Not only is the fan switching on and off every single time your a/c compressor cycles, but the second fan isn't necessarily even required when the a/c is on. All of this is terrible on the electrical system.
Does anyone know if the OEM 05+ harness can be used with the 2 pin method on 99-02 PCM?
Pin 42 - empty - Fan 1 Control - This will be empty on 99-2002 harnesses. A pin can be added for electric fan control. Programming will enable the fan control. PCM supplies a GROUND to turn on a relay. If you have two fans, keep reading, pin for fan 2 will be on the RED connector C2. You must wire your fans through a relay.
Pin 33 - Dk Green - Fan 2 Control - some 99-02 harnesses will have a pin here, this was used for the HVAC Recirculation Door control. The PCM would control the A/C recirculation to help cool the a/c system if it got too hot. In an engine swap, programming can be changed to let this control a second cooling fan. Again, PCM supplies a GROUND to run on a relay. You must wire your fans through a relay.
Here is some additional information that hopefully will clear up some issues in this thread:
1) Radiator size - this is the size of the core. 34" is what you definitely need to use the 05+ fans.
2) A radiator with oil cooler is no problem, just block off those passages in the radiator if you don't have an oil cooler. I have a radiator like this and although I have bought the oil lines/cooler, I have not installed them yet.
3) When using the factory harness, don't cut off the GT150 connector for the PCM leads. All you need is the female GT150 connector and some of your own wire to run to the PCM. Of course, if picking the harness at the junk yard, just make sure to take this complete connector. If you need the GT150 female side connector, I found one here with the terminals seals and lock. Delphi GT150 Series 2 Way Female Wiring Loom Connector
4) You can definitely use the factory harness and control the both fans through the PCM for 1999-2002 models. I believe GMCtrk has a 1999 and did this, nonnieselman did this with his 2000 and I have done this with my 2002
5) A cool little tool when working with connectors and terminals is this removal tool
6) Using the 05 fan settings as previously posted is a good way to go. However, I own an '02 and decided to go with 2002 Camaro fan settings and have had no issues whatsoever
7) Just to clear up any misconceptions about fan speed: the fans do not have separate speeds. A particular fan will at a particular RPM based on the voltage that is receives.
When both fans spin at "low speed", it is because they are in series, thru the use of the relays, and are receiving 6 volts each.
When a fan is at "high speed", it is because the fan is receiving a full 12 volts of power, because now the fans are in parallel mode.
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1. There was a little conflicting information from the OP then a couple posters. I am doing this to a 2002, and wanted to make sure that this was more of an evolving bit of information in that I do NOT have to wire this up to the AC clutch. (I am in Phoenix, where it can be possible to sit in 120 degree traffic at a standstill for 5-10 minutes, and that's if there are NO accidents stopping traffic. I roll with the windows down even when its up to 106 out. I do not feel comfortable having my fans set to the AC clutch. I believe this has been confirmed, but like a few others in this thread, I wanted to confirm.
2. I got a complete harness out of a 2007 classic with all the connectors attached ($20 junkyard pull)... The green and blue wires that are on the connector are the two wires that I will need to hook up. Is there any difference in cutting the two wires and adding the connectors for the board as opposed to making a small little pigtail that is the female to the connector and adding ohhh 6" of wire and the connectors? (Why? you ask; a little cleaner).
3. Is pin 33 also set up as a positive signal from the PCM, (which as I understand it, is the reason you need the relay,)? If its a negative signal or if this is something that can be changed in the PCM, then would I not need that extra relay?
4. The part numbers for the 05-06 electric fans are superceded by the electric fan for the 07-13 fans. The fans look similar, except for the fan blades instead of being a 7 blade and a 5 blade are dual 7 blade. I am assuming this would be a better option because more blades should create a greater cfm. I believe there are 2 options for the 07-13 fan assemblys, with or without "EXTRA DUTY COOLING" Not sure if would have to do with a transmission or oil cooler, and whether or not this would matter.
Not to offend, but I am sure someone will say "just use the 05-06 fans, they work", but this information would open up a lot more possibilities for future modders, these newer fans appear they should flow more, and cost less...
5. Is there any reason I couldn't have this done at the dealer, then go swap this over when I have the time? Is there a reason this NEEDS to be done at the same time? I am thinking the settings would just "sit dormant" until you did add the circuits in to the pins.
For those that come across this thread in the future researching putting e-fans in the 1999-2002 trucks, here is a shameless plug for an article I just wrote up to give you proper high and low speed control of the fans based on the A/C high side pressure just like the 2003-2006 trucks do.
I have a 2001 suburban. Wired everything up using pin 33 and pin 42 and had fans enabled.
Has anyone had issues where their fans come on as soon as the truck starts? The fans come on low speed and never trigger over to high with A/C on. But using tech2, I can trigger the relays without issues and get low speed, single high speed and both on high speed depending on what combination of the 3 relays I trigger.
i also have the A/C compressor that has the high pressure switch on the back and below are the settings from my tuner.
And it seems odd that he has the fan enable setting at 30 mph. Wouldn't that keep the fan from coming on until 30 mph?
If you want it to hit the high speed fan rev to about 2500 while parked with the ac on, it should build the pressure up closer to 300 if your freon is full and then kick the high speed on.
I had previously disconnected both the low and high pressure switches for testing and had the same results. After further testing I realized I had a second high pressure switch by the passenger headlight I was not aware of and upon disconnect, the fans turned off. I just ordered a replacement switch as I believe the switch had failed from a previous overpressure in the A/C that cause the other high pressure switch on the compressor to shoot out of the back. Once I replace that I think it will give me a better starting point. Wish I had known sooner that I had two darn high pressure switches!
Unfortunately i spoke to soon, i had not realized that my harness had not been plugged back in to the ECM when i tested disconnecting from the high pressure switch. This morning when i took a look i realized the mistake and hooked it back up and the fans came back on without the high pressure switch connected by the headlights. I suppose i could try disconnecting both and see if there is any difference but I have a feeling there will not be. When i have a chance I will hook up my Tech2 and see if i can find out what pressures I am seeing
I am also not sure if the tuner I am working with knows how to flash a new OS on to the ECM, as they predominately only do turning on and off pins for fans i believe and are all the way out in Maine where as I am in Maryland.
09-24-2017, 09:37 AM
