Set up e fans with a custom relay harness on on a 99 silverado.
Used pin blue 42 and red 33 (green wire).
I dont have his specific tune on my phone to upload currently but what should the pcm settings be?
I used the setting i found online here but it seems like both fans will run at the same time and i dont believe they run on high speed just low.
Also i heard the early trucks had some issue runnig e fans. Any input is appreciated.
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
i have mine set that way .but i run 3 relays one for low one for high and high only with a/c on
learning
What is pin 33 used for? The way I have understood is that the older ecu's only used pin 42 and then you tap into the a/c request in the fuse block. Engine temp alone turns both fans on low. A/C on will turn the right fan on high, when under the set temp. A/C on and above the set temp will turn both fans on High.
Sith it says HVAC circulation door control.
I also though the fan request signal as well. Bc it would wet the fan on when the AC came on.
I dont remember where he got the 3 relay control. But i just followed the directions and what wires to tap.
Heres a picture
Screenshot_20190514-200448_Chrome.jpg
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
Red 17 is the ac request signal. I personally think that would make more sense than the directions say for a 99
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
From gmfullsizetruck page
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
So now am i tapping into ac clutch wire pin 43?
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
I connected to the a/c request green wire coming out of the fuse block on the driver side fender (per instructions for the kit i used). I also remember it talking about the HVAC door tap. I had elected not to use it thinking it would effect the operation of the HVAC door. You dont have to change any ECU settings unless you want to change the way the fans operate.
I guess the problem here now is the fans only run on low.
Never on high speed.
What controls high speed?
Whenever fan one comes on at the requested temp fan 2 comes on at the same time.
Weve used the pin 33 as well as 43 not 17 yet and the fan will not come on even when using bi controls to activate the ac clutch. Both fans come on low when i use the bi controls to turn on fan 1.
Maybe im overlooking somthing here.
The posted tune i changed fan 2 settings they were incorrect so it doesnt match acutal tune in vehicle tho i dont think fan 2 matters with older sytem.
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
Lets start with being specific about which aftermarket fan relay harness you have. There are 2 different designs. One for 99-02 trucks and one for 03+. The 99-02 design has one wire to add to the PCM connector and one to the A/C clutch +12v feed. The 03+ design has 2 wires to add to the PCM connector.
cooling fan.pngFan Control.pngHVAC.pngNumber of Fans.png
The fan wiring diagram is from a 1999 Camaro and is what I have used for wiring on the LS swaps I have done. The other diagram is the HVAC control from a 1999 Silverado 1500 5.3L. The sensors for the A/C all go to the PCM so when all the conditions are met the PCM turns on the fans for A/C. It also know the coolant temp so it turns them on for that also. The HPTuners pictures are how to choose the fans and the recirc door option. If your vehicle has really high A/C pressure it will force the HVAC module to move the A/C recirc door to to use only inside colder air to try and lower A/C pressures so no damage is done. I have never worried about that option because I live in a small town in a colder climate. There are very limited times that I am in stop and go major highway traffic where A/C temps would be a concern. There is still a A/C high pressure switch to try and protect the system but it is probably set to 425PSI before it shuts off the A/C. I have always used regular relays for the wiring not aftermarket fan controllers and I have had good luck. I have heard stories about early PCM's not controlling fans but I have not seen it yet. I hope this helps or at least has some useful info.
Last edited by BlazerDave; 05-22-2019 at 04:21 PM.
He got the relay harness from ls1fans.comOriginally Posted by 2xLS1
It had one wire with pin to connect to blue 42 and another wire that needed to be tapped into an ac wire.
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
You can control both fans using a 99 PCM -- I just did this to my 99 6.0L LQ4 truck, here are the settings you need:
Settings for 1st fan:
System > Fans > Hardware > Fan Type = 2 Fans
System > Fans > Ignition Off > Enable Temp = 230*F
System > Fans > Ignition Off > Run Time = 30s
System > Fans > Fan 1 (First Stage) > Min Time = 5s
System > Fans > Fan 1 (First Stage) > Fan Disable Speed = 30mph
System > Fans > Fan 1 (First Stage) > Fan Enable Speed = 29mph
System > Fans > Fan 1 (First Stage) > Off ECT = 200*F
System > Fans > Fan 1 (First Stage) > On ECCT = 209*F
I had not yet wired the second fan yet, I added the following settings once I added a wire to pin 33.
(I may have removed the old pin first, I don't recall. Regardless, the ECU never actually uses the recirculation, its got a separate control wire to the A/C controls that does the real work.)
Settings for 2nd fan:
System > A/C > Hardware > Recirculation Fitted = Fan #2
System > Fans > Fan 2 (Second Stage) > Min Time = 5s
System > Fans > Fan 2 (Second Stage) > Off ECT = 204*F
System > Fans > Fan 2 (Second Stage) > On ECT = 215*F
These settings are working great for me. You can use VCM Scanner to command fan 1 or fan 2 ON/OFF to test that your wiring is correct. Bidirectional control lets me enable both fans individually (I used a 2 relay setup), if yours isn't working like this you have a problem somewhere
I do not have a tap into the A/C request line since it isn't hot here yet, I am controlling both fans from the PCM. I will be adding a 2nd trigger to fan 2 using the A/C clutch line come summer. This will require a trouble code to be disabled, I don't recall the code number right now, but it sets a code when it detects ground on a fan control line when it hasn't requested to turn a fan on. Doing it this way maintains high / low fan control through the PCM, but also runs a fan with the A/C. If I was using a 3 relay setup for high / low, I would run this 2nd trigger to fan 1 instead to run both fans on low with A/C. Where I am using a 2 relay setup, I wanted to distribute the fan run time between both fans and so will be wiring AC to fan 2.
Last edited by Tiron; 05-22-2019 at 04:53 PM.
That is not the way the harness he has will work. High speed fans will only be controlled with the 12V wire that turns on the AC compressor clutch and has to be connected to that wire. The PCM outputs grounds on the fan control wires and the harness he has will not turn on high speed with a ground trigger. Only a 12V trigger. You need the harness for the 03+ trucks to work with those settings.And it takes 3 relays to control both fans running low speed (fan1) or both fans running high speed (fan2). You can not do that with only 2 relays.
Last edited by 2xLS1; 05-22-2019 at 08:15 PM.
Wait wait wait . Your saying the harness im using will only activate with a 12 volt trigger and the ac clutch wire from the pcm is a ground trigger?
If so i have to run my other wire to the 12v trigger in the ac clutch relay?
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
Ok going by what 2XLS1 said i think i understand my faults now.
I would use this dark green wire from the relay.
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
Got it to work by using the AC relay green wire.
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
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