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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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I have my fans in and upgraded to 145 amp alternator. I've tied into pin 42 on the blue pcm connector and had the pcm tuned. Low speed is working great. Pin 33 isn't available on either connector. Is it another pin I need to tie into for the AC/right fan trigger? Or tie into an existing wire coming from the pcm? I have a 99 GMC Sierra 6.0L.
Pin 33 is probably for the auto recirculation...my truck did not have that so the slot was empty.
Just read your post earlier in the thread. Thanks. Does the fan turning on replace the need for auto recirculation? Do i just cut the wire and run it to fan 2 relay and have the shop program it so pin 33 is fan 2 control instead?
I have done this same swap on my truck. The question I have for you is about the operation of the fans running. Do the fans run as soon as the engine is turned on? My fans come on as soon as the engine starts and stay on low speed then high when a/c is on, is this normal?
I have done this same swap on my truck. The question I have for you is about the operation of the fans running. Do the fans run as soon as the engine is turned on? My fans come on as soon as the engine starts and stay on low speed then high when a/c is on, is this normal?
On my truck, the fans do NOT come on immediately unless the AC is on. If the AC is on, the high speed fan will come on. The low speed comes on only when the engine is up to temperature (210° on my truck is when they are set to come on). Both fans will run on high if the temp is above 210° AND the AC is on. If your fans are always coming on low even if the truck is cool, then you have something wrong with the green trigger wire. Either it is grounded somewhere, its not inserted properly into pin 42 on the PCM, or else you you do not pin 42 programmed properly with your engine tune.
Very good write up. I do have a question, is there anyway to wire up the fans and have them work as designed without having my computer sent off to be tuned? I have an 04 Sierra. I have been looking at the thermostat controlled harnesses on amazon and want to know what everyone thinks.
Very good write up. I do have a question, is there anyway to wire up the fans and have them work as designed without having my computer sent off to be tuned? I have an 04 Sierra. I have been looking at the thermostat controlled harnesses on amazon and want to know what everyone thinks.
The absolute most reliable way to do it is to wire it up with a factory harness and get the PCM tuned. I've seen some other truck forums where people added an external coolant temperature sensor and used that to turn the fans on and off, and wire the other trigger wire to the AC clutch. On my own truck, I have the high speed trigger wire spliced into the AC clutch wire, with a relay to convert the positive voltage on the clutch to a negative to trigger the relays on the factory fan harness. The low speed/temperature wire is connected to the PCM and is triggered by the factory coolant sensor. So it basically preforms EXACTLY like it would from the factory.
Aug 29, 2015 | 09:44 PM
