So much info but all confusing info
What settings allow 896 ecu run a factory dual fan setup/harness, with
proper functioning a/c and a/c on fan on.
And does the above settings require a added relay for a/c trigger + to a -
ground fan relay trigger ? i seen the writeups but no idea on their specific ecu
settings/programming.
completely stock truck and do not wish to change OS
On my 2000 GMC I got a later model fans with wiring harness and one wire goes to the ECM then in the tune you turn the fan on, it is really easier than it sounds, kinda self explanatory.
You do have relays but they are pretty easy to figure out.
I have done 3 efan conversions now. Mistakes were made and lessons learned!
You are spot on that there is lots of info and it can be confusing. There is definitely a thread (or 3) that goes over all the specific fan settings and even has a fan tune to compare. Just search.
I found it worked best for me to get the factory wiring harness and fans from a junkyard. Cost 50 bucks for everything.
The advantage of the oe setup is everything connects easily. Just make sure you get all wires that connect to the 3 relay group and put them back where they were located. If one of the pin locations that you need (33 42) is full just remove and replace. That is just for ac recirculation. You will be shutting it off anyway.
The aftermarket harnesses works well too. Nelson Performance sells a good one but you have to locate and tap into an ac wire. Good luck.
So i take it nobody got the 896 ecu to work with electric fans.
Did not see any settings that actually works, and tried quick
tests and each time pin is ground constantly.
I have efans with the 896 ecu.
I have the LS1Fans 99-02 Truck Harness (1 wire into ECM and 1 wire wiretap the ac relay) and electric fans off an 09 Escalade.
Once I got everything wired up and had the temps I wanted the fans to come on at set in the tune. But of course things didn't work right on the first try.
The two important changes I forgot were:
1: In the "System" Menu, under the "Fans" tab, change "Fan Type" drop down to "2 Fans". Stock was "No Fans". (Kind of a duh, but I forgot lol)
I did that, but fans would still come on as soon as I started the truck.
2: In the same "system" menu, but under the "A/C" tab, change the "Type Fitted" drop down to Analog. The stock setting for me was Analog Cycling, but changing it to Analog made everything work.
For whatever reason the difference between Analog and Analog Cycling is voltage supplied to Pin 42. I forget what thread I read about this in.
Again, this was for the adding 1 pin to the ecm and 1 wiretap on the ac relay style harness. I don't know the first hand effect of the Type Fitted drop down on the 2 ecm pin style harness, but it is worth messing with since it controls the default voltage going to at least pin 42.
Edit found the thread: AC Recirculation
Looks like that guy was using pin 42 and pin 33 style harness. Looks like switching Analog Cycling to just Analog is the important thing here.
Last edited by 07sgguy; 12-21-2021 at 08:56 PM.
Post your tune?
Yea ive done several 99-00 trucks with Efans. I never use the A/C tap since it cycles the fan when the A/C compressor cycles. It burns up relays.
Its no problem at all going to a 2002 operating system tho.
93 Octane.hpt
I've heard about the relays burning up. Mine never get any warmer than anything else in the engine bay that isn't the engine. My guess is that happens from the wrong settings in the tune.
Alternatively, I've heard people complain it burnt up cause the ac kept cycling on and off. That's not a fan problem, the excessive cycling is cause the ac needed refrigerant.
At any rate, I haven't had any problems whatsoever.
Its not that they get warm while in use. Its the cycling that kills the relay contacts. They are only good for so many cycles.
And the A/C Compressor will cycle often when the HVAC fan speed is low. If the fan is on high then usually the A/C will stay engaged.
Interesting. Like I said, I haven't had any issues. Once I got my system charged, the a/c compressor would just stay on when I wanted ac, regardless if it was full blast or just barely on. That being said, I know my ac system is leaky and 21 years old, so I know it's not at 100% efficiency.
Thank you for the responses
set it up on my bench harness on a second 896 ecu to rule bad ecu out.
99 silverado 372 os
pin 42 blue, is always ground as soon as ign switched on
no matter analog or analog cycling or any other type.
fan 2 or a/c rec still same always grounded
Tried write cal as well as write entire, still grounded as soon as ignition on
WHAT OS are your files that have worked ? curious if it is a OS issue
07sgguy your tune file says cannot open as it is a remote network ???
RDF1 how are you trigging fan 2 without a/c tap ? works with on temp settings ?
I always go straight to the 2002 OS. 12212156.Originally Posted by kjnman
Wire ground triggers to 33 and 42.
Ive never tried to test it on a bench tho.
unfortunately there are some operating systems that absolutely will not operate both fans no matter what settings you put in. We do tons of swaps, and find this often, upgrading to a different known good os corrects the problem 100% of the time.
Michael Bray
Rusty Knuckle Garage
Slidell, Louisiana
20yr Master Tech.
Advanced Level Specialist
Custom Car Fabrication, Customization, High Performance.
GM World Class Technician
Shop Owner
mbray01 thank you for the insight
Would there be a known list of OS that do NOT work for fans ?
helps now and for future references as well as for everyone else working
through the issues i am having.
Last edited by kjnman; 12-23-2021 at 11:35 AM.
hi everyone so this is my first time posting anything and ive been having an issue trying to figure out how to create a post for my issue...
i have hp v4.10 and want the old fans settings back instead of the desired% vs ECT
to me the old style where you can control the exact temp when to turn on was the best thing so anyone has any ideas?
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