Running A/C with Holley EFI

Zmar93

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1993 K1500 silverado. I've been looking through my Haynes manual wiring trying to figure out the correct way to wire a Holley sniper unit into the factory a/c. Im thinking a ground triggered relay is needed? I know the Sniper A/C IAC Kick wire uses ground so I cant hook directly to compressor clutch + wire. Has anyone done this before?

Also wondering if I can connect the stock 93 tach to the sniper without issues? I also need to locate that tach wire. I eliminated alot of un-needed wiring 15 years ago when I put a carb on.
 

Erik the Awful

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I haven't wired up the A/C on my Sniper conversion yet, and looking at the diagram, it looks like it's not a simple plug-n-play. The diagram I found shows putting a relay in parallel with the A/C clutch circuit. When the clutch is energized the load contacts ground the Sniper's A/C kick. That looks like the simplest way to do it.

My '89 doesn't have a tach, so I don't know about that.
 

bluex

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You don't need to wire the a/c through the sniper. It can accommodate the extra load without needing the input. If you really want to wire it though use the clutch signal to trigger a relay that switches a ground signal that you put on the sniper wire.

As far as the tach goes the sniper has an output for it, you can also watch it on the handheld an if you mount it where you would a tach you'll have tons of info in the same location.
 

Zmar93

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Ok thanks. I was hoping there might be a simpler way. I will add in a relay since I'm worried about ac at idle. Not sure yet how it will work with efi but with the carb I had to run an ac solenoid to bump idle up, it's a high compression 355 lopey cam.
 

bluex

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It will see the idle dip from the extra load an open the iac more to compensate. Shouldn't cause any issues. I have 2 personal setups that work fine without the a/c input an I've done several other installs for other people that work fine without it too.

The reason you needed the bump with the carb was because it couldn't vary the idle past what you set with the screw. On the sniper you set the screw to an IAC count of 2-10% at operating temp (get as close to 2 as you can). The IAC then has from 3-100% to add additional airflow to maintain idle speed when the engine is loaded (placed in gear if auto, a/c clutch engages etc)
 

Zmar93

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I'm all for less wiring.... I'll try running a/c without first.

Im thinking the original tach wire is the white wire in the factory distributor 4 pin plug. I'll likely use the sniper screen anyway just wondered if a guy could make the factory tach work right again.

One other question.. Whats the easiest way to correct my speedo calibration for tire size? I'm trying to reconnect and run the factory cruise again also.
 

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I can't help with the speedo but the factory tach should still work if you hook the sniper output to it. It does in my 95 anyhow.
 

ShawnB

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i can add to the AC input side as well, i have a FiTech ES600, it only raises rpm by 50 out of the box...i can adjust that, but it raises back to my predetermined setting once it loads down. i have mi idle set at 850, and it seems smooth ( handheld bounces anout 55-75 rpm, i have the handheld set for fastest response also)
 

Zmar93

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I recently finished the sniper efi install. It's a nice clean install. Took alittle longer than planned but its right. I did NOT connect the a/c kick wire. Adjusted IAC to 3% Idling around 670rpm it does not drop idle rpm when compressor kicks in. This works excellent. So far I'm impressed with the sniper setup. Tach is still inop I need to look into more.
 
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