How are you putting fans on when running VA AC - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**1970 CST Short Wide** · 01-29-2017, 01:35 AM

I understand that the fans (electric) need to be on when your AC is on. I have vintage air. How are you guys running your fans when the AC is on??

Thanks
Steve

**dec010974** · 01-29-2017, 05:18 AM

Good morning 1970 custom. I'm gonna assume that you are referring to the electrical part right? In most cases the LSx pcm commands the fans to run when the engine reaches a certain temperature. If you want your E fans to turn on when the A/C is turned on just set up the fan relay trigger off of the A/C on switch. This means that when you turn on your A/C, it will trigger your fan relay to turn on your fans. I hope this helps you out. This is my answer. There may be others.

#30-Fused Battery power
#87-Power to E. Fan
#86-Ground
#85-Power side of A/C on switch.
Note:#85 is not the power for the A/C. #85 will be the power/trigger once the A/C is turned on or maybe even the A/C clutch switch. Good luck.

ls1nova71 · 01-29-2017, 11:24 AM

Easiest way is to use a trinary switch.

**dec010974** · 01-29-2017, 12:25 PM

ls1nova71, I gotta read up on this thing called a trinary switch. most of my hot rods don't have A/C.

my56chevytruck · 01-29-2017, 12:29 PM

use a trinary switch and or a wired switch in the cab to activate your fans.

homemade87 · 01-30-2017, 09:12 AM

I agree with the trinary switch . Lots of advantages going thru the pcm . Best to have a dual fan set up with the three relay system but can be used for a single fan . The trinary uses the high pressure side to control the fans .

Here's where I did mine and it works perfect . http://67-72chevytrucks.com/vboard/s...hlight=trinary . Also just type in trinary and you will see a lot of info . In my opinion this is to only way to go .

**Hart_Rod** · 01-30-2017, 09:49 AM

Trinary wiring diagram

68c10airstream · 01-30-2017, 11:31 PM

If you can get the pcm involved in the on/off command of the compressor the pcm will automatically adjust the idle rpm for the incoming load and unloading. Without the pcm involved i believe you may get an idle undershoot/overshoot. On my gm pcm #411 it has an input called a/c request and this circuit is what i will be using in my ls ac system once my house from hell projects get finished.

ls1nova71 · 01-31-2017, 12:04 PM

The IAC, or DBW throttle body as the case may be, will compensate for any additional load on the engine. I have most of my swaps run this way and have never had any problems with it.

davepl · 01-31-2017, 02:00 PM

If I understand it, and I'm not sure I do, a trinary switch is a fancy scary way of saying

"A pressure switch with two sets of on/off leads".

The leads are diagonally opposed. What goes in one corner comes out the other corner when the pressure is met.

**Hart_Rod** · 01-31-2017, 02:43 PM

Quote:

Originally Posted by davepl

If I understand it, and I'm not sure I do, a trinary switch is a fancy scary way of saying

"A pressure switch with two sets of on/off leads".

The leads are diagonally opposed. What goes in one corner comes out the other corner when the pressure is met.

High & low pressure safety cutoff switch and a direct signal to turn on E-Fans.

01-29-2017, 01:35 AM	#1
1970 CST Short Wide Senior Moment Join Date: Mar 2002 Location: Pittsburg Ca Posts: 4,187	How are you putting fans on when running VA AC I understand that the fans (electric) need to be on when your AC is on. I have vintage air. How are you guys running your fans when the AC is on?? Thanks Steve __________________ 1970 CST LS 1 6 speed Ford 9 inch Detroit Tru Track, Dakota Didgital, Vintage Air, QA1 Coil Overs Front & Rear Lots of FUN 2013 GMC PU, Oldest Son 71 GMC LWB. QA1 Suspension, Angry SB. Youngest Son 2019 GMC Diesil Dually. Youngest Son 2017 Toyota SUV Daughters car 2018 Traverse , Wife’s Ride Pittsburg Ca 94565

01-29-2017, 05:18 AM	#2
dec010974 Senior Member Join Date: Oct 2012 Location: Miami, Florida Posts: 959	Re: How are you putting fans on when running VA AC Good morning 1970 custom. I'm gonna assume that you are referring to the electrical part right? In most cases the LSx pcm commands the fans to run when the engine reaches a certain temperature. If you want your E fans to turn on when the A/C is turned on just set up the fan relay trigger off of the A/C on switch. This means that when you turn on your A/C, it will trigger your fan relay to turn on your fans. I hope this helps you out. This is my answer. There may be others. #30-Fused Battery power #87-Power to E. Fan #86-Ground #85-Power side of A/C on switch. Note:#85 is not the power for the A/C. #85 will be the power/trigger once the A/C is turned on or maybe even the A/C clutch switch. Good luck.

01-29-2017, 12:29 PM	#5
my56chevytruck Registered User Join Date: Feb 2016 Location: Hebron Posts: 1,153	Re: How are you putting fans on when running VA AC use a trinary switch and or a wired switch in the cab to activate your fans. __________________ RUBBER DOWN AND HIT THE ROAD!!! 1940 Ford Dlx Coupe 1969 Mach1

01-30-2017, 09:12 AM	#6
homemade87 Registered User Join Date: Apr 2010 Location: Guntersville Alabama Posts: 1,073	Re: How are you putting fans on when running VA AC I agree with the trinary switch . Lots of advantages going thru the pcm . Best to have a dual fan set up with the three relay system but can be used for a single fan . The trinary uses the high pressure side to control the fans . Here's where I did mine and it works perfect . http://67-72chevytrucks.com/vboard/s...hlight=trinary . Also just type in trinary and you will see a lot of info . In my opinion this is to only way to go .

01-30-2017, 09:49 AM	#7
Hart_Rod ************* Join Date: Apr 2005 Location: Pensacola, FL Posts: 17,858	Re: How are you putting fans on when running VA AC Trinary wiring diagram Attached Images __________________ Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3

01-29-2017, 11:24 AM	#3
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: How are you putting fans on when running VA AC Easiest way is to use a trinary switch. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

01-29-2017, 12:25 PM	#4
dec010974 Senior Member Join Date: Oct 2012 Location: Miami, Florida Posts: 959	Re: How are you putting fans on when running VA AC ls1nova71, I gotta read up on this thing called a trinary switch. most of my hot rods don't have A/C.

01-30-2017, 11:31 PM	#8
68c10airstream Registered User Join Date: Mar 2013 Location: Marquette michigan Posts: 828	Re: How are you putting fans on when running VA AC If you can get the pcm involved in the on/off command of the compressor the pcm will automatically adjust the idle rpm for the incoming load and unloading. Without the pcm involved i believe you may get an idle undershoot/overshoot. On my gm pcm #411 it has an input called a/c request and this circuit is what i will be using in my ls ac system once my house from hell projects get finished.

01-31-2017, 12:04 PM	#9
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: How are you putting fans on when running VA AC The IAC, or DBW throttle body as the case may be, will compensate for any additional load on the engine. I have most of my swaps run this way and have never had any problems with it. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

01-31-2017, 02:00 PM	#10
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: How are you putting fans on when running VA AC If I understand it, and I'm not sure I do, a trinary switch is a fancy scary way of saying "A pressure switch with two sets of on/off leads". The leads are diagonally opposed. What goes in one corner comes out the other corner when the pressure is met. __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible



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