Does LS ECM controller have AC input pin? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

flipper58 · 05-08-2020, 11:55 AM

Finishing up the wiring on my LS conversion with the help of my brother (my wiring pro). We are about to connect the fans, AC, etc. into the underhood fuse box provided with the Connect and Cruise LS engine kit. He posed the following questions and I thought someone on this forum might know.
Thanks,
Phil

Does the Gen III engine controller have an AC input pin? If yes, will the engine controller turn on the engine cooling fans when the AC is turned on?

**PGSigns** · 05-08-2020, 08:35 PM

You may want to post this in the ls swap section. Maybe an admin can move it.
Jimmy

**Richard** · 05-08-2020, 09:54 PM

There is some information you may be looking for in this post http://67-72chevytrucks.com/vboard/s...d.php?t=776599

lutronjim · 05-08-2020, 10:08 PM

I just posted this but it didn't show up. Hopefully this wont be a dup.

When I hooked up my 'connect and cruise' I ran the wire from the harness marked fan to the fan motor and the other side of the motor to ground. When the ECM wants the fan to run, it triggers a relay in the fuse box to put out a fused 12v+ -- not a ground like most stuff.

I then used the signal to the AC clutch to trigger a separate relay to sent 12v+ to the fan.

If the AC is running the fan will turn on. If the ECM wants fan it will turn on. If they both want fan, it still comes on with no chance of a back circuit.

Hope this helps.

flipper58 · 05-08-2020, 10:28 PM

Thanks gents for all the leads. It gets me heading in the right direction.
Phil

Andy4639 · 05-09-2020, 10:02 PM

The ECU should have a pin for the fans and as stated above it's 12 volts + not the ground.

I hooked mine up like this.

**Richard** · 05-12-2020, 04:35 AM

Quote:

Originally Posted by lutronjim

I just posted this but it didn't show up. Hopefully this wont be a dup.

When I hooked up my 'connect and cruise' I ran the wire from the harness marked fan to the fan motor and the other side of the motor to ground. When the ECM wants the fan to run, it triggers a relay in the fuse box to put out a fused 12v+ -- not a ground like most stuff.

I then used the signal to the AC clutch to trigger a separate relay to sent 12v+ to the fan.

If the AC is running the fan will turn on. If the ECM wants fan it will turn on. If they both want fan, it still comes on with no chance of a back circuit.

Hope this helps.

One hiccup I see with this setup is the fan will be running at highway speeds which is most likely not needed.

gmc684x4 · 06-10-2020, 11:33 PM

On a aftermarket setup the fans are on by temp only with no speed input

Of ecu signal i am not sure if it would take speed into account
In both cases you will need to run power to the fans through relays anyway

If i where out 4x4 in slippery conditions i would want fans on by temp only

05-08-2020, 11:55 AM	#1
flipper58 Registered User Join Date: Sep 2013 Location: Pleasant Ridge, MI Posts: 285	Does LS ECM controller have AC input pin? Finishing up the wiring on my LS conversion with the help of my brother (my wiring pro). We are about to connect the fans, AC, etc. into the underhood fuse box provided with the Connect and Cruise LS engine kit. He posed the following questions and I thought someone on this forum might know. Thanks, Phil Does the Gen III engine controller have an AC input pin? If yes, will the engine controller turn on the engine cooling fans when the AC is turned on?

05-08-2020, 08:35 PM	#2
PGSigns Senior Member Join Date: Jan 2011 Location: Hayes Va Posts: 4,569	Re: Does LS ECM controller have AC input pin? You may want to post this in the ls swap section. Maybe an admin can move it. Jimmy __________________ 60 to 66 Chevy and GMC window decals http://67-72chevytrucks.com/vboard/s...d.php?t=661131 Good friends, good food and a hotrod what else do you need? 1966 BBW long fleet Daily driver 1965 BBW short fleet Sold and going to a good home 1965 Suburban 2003 3500 Duramax 2005 Ultra Classic

05-08-2020, 09:54 PM	#3
Richard Senior Member Join Date: Dec 1999 Location: Southern California Posts: 2,695	Re: Does LS ECM controller have AC input pin? There is some information you may be looking for in this post http://67-72chevytrucks.com/vboard/s...d.php?t=776599 __________________ Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746

05-08-2020, 10:08 PM	#4
lutronjim Registered User Join Date: Dec 2013 Location: Dunwoody,Ga Posts: 443	Re: Does LS ECM controller have AC input pin? I just posted this but it didn't show up. Hopefully this wont be a dup. When I hooked up my 'connect and cruise' I ran the wire from the harness marked fan to the fan motor and the other side of the motor to ground. When the ECM wants the fan to run, it triggers a relay in the fuse box to put out a fused 12v+ -- not a ground like most stuff. I then used the signal to the AC clutch to trigger a separate relay to sent 12v+ to the fan. If the AC is running the fan will turn on. If the ECM wants fan it will turn on. If they both want fan, it still comes on with no chance of a back circuit. Hope this helps.

05-08-2020, 10:28 PM	#5
flipper58 Registered User Join Date: Sep 2013 Location: Pleasant Ridge, MI Posts: 285	Re: Does LS ECM controller have AC input pin? Thanks gents for all the leads. It gets me heading in the right direction. Phil

05-09-2020, 10:02 PM	#6
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Does LS ECM controller have AC input pin? The ECU should have a pin for the fans and as stated above it's 12 volts + not the ground. I hooked mine up like this. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

06-10-2020, 11:33 PM	#8
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: Does LS ECM controller have AC input pin? On a aftermarket setup the fans are on by temp only with no speed input Of ecu signal i am not sure if it would take speed into account In both cases you will need to run power to the fans through relays anyway If i where out 4x4 in slippery conditions i would want fans on by temp only



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