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Here’s My Holley Terminator Max A/C Wiring Diagram
I recently switched over to a Holley terminator x efi after swapping my 5.3 to a 6.0. For years I ran a psi conversion harness with an ls1 pcm and the a/c ran through the factory 3 wire high pressure switch. I had no need for a shutoff relay being the pcm took care of everything. I ended up coming up with this diagram for the Holley system and got my a/c working. I use to search for this stuff when I was doing my swap years ago, so hopefully it helps someone else out.
It’s a little crude and hard to read, but it works! The Holley pcm controls the a/c through 3 wires. It takes the 12 volt input signal from the 3rd gen controls and uses that as the idle kick up and a/c command signal. It then turns the fans on and grounds the compressor relay through the Fan 2 output wire, gray/red stripe. I couldn’t figure out how to switch the function of the outputs, so I just used the fan 2 ground signal. The Holley pcm has 8 inputs and outputs, 4 each. The issue is that some are pre programmed for launch control, converter lockup, and a second fuel pump in their own menus. To avoid messing with those, I decided to just use the second fan wire being it was already a ground output.
My fans are both controlled by individual relays, both grounded by the single fan 1 output wire. Being both fans will be triggered when the a/c is requested, I figured that would work perfectly to ground the compressor relay. I maxed the fan 2 temp to 300 degrees on, 299 off. This will ensure the a/c doesn't come on whenever the fans do. For temp sensors and compressor cycling, I utilized the factory low pressure sensor, and will add a universal 2 wire high pressure sensor soon. I couldn’t figure out how to use the 4th gen 3 wire sensor, so I left it out for now.
Both of those sensors are normally closed under most operating conditions. This allows the current to flow to the trigger side of the compressor relay from my 12 volt ignition source on the car’s harness. When the pressure gets too low, the thirdgen switch opens and cycles the compressor. Same thing goes for the high pressure switch if there was to be some kind of failure. The ignition voltage to the compressor relay needs to pass through the shutdown relay first, this gives us our cut out point for wot.
The 3rd and final wire that the Holley uses to control the system is the cutout wire. The bottom cutout relay is wired through the 87a terminal which is always closed. This allows constant power to the compressor, but once the pcm sees wot or a condition to turn off the a/c, it grounds that cutout relay, opening the connection on 87a and cutting power to the compressor relay.
As for the 12 volt connections to the car’s ignition, all three of those wires are connected to the same source. I used a wire from one of the old 3rd gen pcm connectors for power. Pretty much the thickest one in the bunch. The cutout and compressor relays won’t be staying on at the same time, so there isn’t a lot of amperage there. I made this into a video, so I’ll probably have it up on YouTube in a week or so.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Glad you got it working.
It seems like a waste to have two relays though, unless you never plan on needing the exta outputs. The Factory TPI doesn't use a relay for the compressor control, I was planning on putting in one relay just to shut the compressor off at high RPM but leave the rest as stock TPI so I have as many outputs available as I can
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by scooter
Glad you got it working.
It seems like a waste to have two relays though, unless you never plan on needing the exta outputs. The Factory TPI doesn't use a relay for the compressor control, I was planning on putting in one relay just to shut the compressor off at high RPM but leave the rest as stock TPI so I have as many outputs available as I can
A clutch really doesn’t use much but with my luck I would have let the smoke out of something...The pcm has an internal relay for the fuel pump, so you can literally just run one wire from the pcm to the pump which is great, but for the rest of the outputs I really don’t know how much they can handle.
The other issue I had was switching them between power or ground. The software has a drop down menu that lets you choose between the two, but it kept giving me an error saying the io pin had to be moved. I went to the io configure tab and tried moving the function to different pins, but I kept getting the same message.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by LsxMatt
A clutch really doesn’t use much but with my luck I would have let the smoke out of something...The pcm has an internal relay for the fuel pump, so you can literally just run one wire from the pcm to the pump which is great, but for the rest of the outputs I really don’t know how much they can handle.
Ummm, ....ok? Not sure how the fuel pump is relevant to the AC
Originally Posted by LsxMatt
The other issue I had was switching them between power or ground. The software has a drop down menu that lets you choose between the two, but it kept giving me an error saying the io pin had to be moved. I went to the io configure tab and tried moving the function to different pins, but I kept getting the same message.
The circuit in the computer can only do one thing, either high or low, it can't do both. So the low based outputs can be on/off or PWM and the high output can only do the opposite.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by scooter
Ummm, ....ok? Not sure how the fuel pump is relevant to the AC
The circuit in the computer can only do one thing, either high or low, it can't do both. So the low based outputs can be on/off or PWM and the high output can only do the opposite.
Ok that makes sense. It mentions in the manual that those specific outputs(fan and ac cutout) are specifically ground outputs. Just the way I interpreted the software made it seem like they could be switched somehow. I mentioned the fuel pump because that specific circuit has its own integrated relay, so it can handle a lot of amperage, unlike the other i/o’s. So you can run the wire straight to the pump, without having to add a relay like I had to do with the compressor. It looks like the other outputs have an amp cap of 2 so depending on the initial spike of the load, the clutch could exceed that. Once again, me and my luck of letting the smoke out of things..
I found some info on the Holley forums which would have helped me earlier. It shows the limits of the i/o circuits and when you should consider a relay.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
I think you've got a problem there, bud. If I'm reading it right, the AC Kick is tied to your HVAC position selector instead of the AC compressor switch. You want the AC kick to trigger every time the compressor cycles on so engine doesn't stall. I think I came up with about 8 or 9 ways to wire AC and each had quirks except this way right here,
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
I also put a 1 second delay time before turning on the AC relay. Gives me a chance to move around the HVAC lever without anything happening until I stay on a spot.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by QwkTrip
I think you've got a problem there, bud. If I'm reading it right, the AC Kick is tied to your HVAC position selector instead of the AC compressor switch. You want the AC kick to trigger every time the compressor cycles on so engine doesn't stall. I think I came up with about 8 or 9 ways to wire AC and each had quirks except this way right here,
I think you can abandon the Shutoff Relay if you want. I don't see it serving a useful purpose.
ahhhh ok. So you have the sensors cutting the request signal so the pcm knows to switch the idle
back. I’ll have to move them over to the request wire then. I went with the cut relay just because I didn’t wanna risk possibly damaging something if I spun it out to redline and forgot to turn the a/c off. Will that even do anything? I never really thought about it but I know the stock setup would always cut off the compressor.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by QwkTrip
Just use the ECM to control the AC compressor relay instead.....
Ok if I knew that I wouldn’t of bothered with a relay. Honestly I haven’t had time to play around with this software so I’m kind of doing everything mechanically the way I know how. The car still has to go for tuning so once its all said and done I’ll have to learn more about the Holley system. Thanks for the help, I completely missed the issue with the kick up signal.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
No worries, I had to wire in AC Kick as an afterthought too. Then my AC system leaked out in 3 days and I've never had AC since. Overall I think you're doing better than me!
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by QwkTrip
I think you can abandon the Shutoff Relay if you want. I don't see it serving a useful purpose.
This is what I was trying to say, although maybe it made more sense in my head. The stock 3rd gen doesn't ues a relay to run the AC compressor at all, so if you use the Holley to control one of those relays you wouldn't have to worry about the Holley burning out. I guess you mentioned the fuel pump circuit because you thought I meant to have the Holley run the compressor.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by scooter
This is what I was trying to say, although maybe it made more sense in my head. The stock 3rd gen doesn't ues a relay to run the AC compressor at all, so if you use the Holley to control one of those relays you wouldn't have to worry about the Holley burning out. I guess you mentioned the fuel pump circuit because you thought I meant to have the Holley run the compressor.
Exactly, I thought you were saying to run the output trigger directly to the clutch. Plus I had no idea you can ditch the cutout wire and program an output specifically for the compressor. I really need to do some reading on the Holley forums, especially since I plan on using the built in 2 step.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
This is good info. I am going a slightly different route as I purchased the AC harness premade from current performance. I have not wired it in yet though. Figured I would share as an option for folks. If it works, lol. Will verify when I get it running.
Re: Here’s My Holley Terminator Max A/C Wiring Diagram
Originally Posted by Sdmodified
This is good info. I am going a slightly different route as I purchased the AC harness premade from current performance. I have not wired it in yet though. Figured I would share as an option for folks. If it works, lol. Will verify when I get it running.
06-11-2020, 07:07 PM
