QwkTrip

iTrader: (22)

I'm looking at how to do AC controls and I would like confirmation from somebody that knows what they are doing. I have a Holley HP system so no LS1 controller. The AC has to be stand-alone. All my blower motor wiring is in tact, but the only thing I have of my AC wiring is what came out of the firewall, so I can build whatever controls I want.

'89 Firebird. I notice there are 3 ways these 'Birds were wired. Each uses the head unit in the dash to power the compressor clutch. The difference is how the power gets to the compressor clutch. All go through the low pressure switch (pressure cycling switch) and from that point,

• VIN F: Goes to high pressure switch --> to compressor clutch --> ground.
• VIN S: Goes to high pressure switch --> A/C relay (controlled by engine ECM) --> compressor clutch --> ground
• VIN 2: Goes to A/C relay (controlled by engine ECM) --> compressor clutch --> ground
• Each version uses engine ECM to bump idle up when compressor clutch is powered.

My car is a VIN S. I don't see any reason to keep the A/C relay, do you? I can just copy VIN F and route the A/C compressor request in series through the low pressure switch, then through the high pressure switch, then to compressor clutch. At that point it will simply be a system that works on the low and high pressure switches.

Meanwhile, #1 radiator fan needs to be on at all times when A/C is on, so tap that relay control off the LT GRN wire from head unit when the A/C is on. And #2 radiator fan should be on when the high pressure switch is closed, so tap that relay control from the low side of the high pressure switch. Does all this sound right? These will be parallel fan controls to the coolant temp based strategy I will use in the Holley HP system.

P.S. How in the world does VIN 2 get by without a high pressure switch???

Restrorob

iTrader: (7)

QwkTrip,

The way you explained wiring your system is EXACTLY the way I had planned on doing mine with the carb swap ECU delete, The only difference is I've got the AC idle kick-up solenoid on my carb which will be wired in with the clutch power lead.

Personally, I see no reason why this wiring system wouldn't work but I too would like to hear from anyone that knows better......

Joe Tag

iTrader: (4)

You also have the issue of turning the fan on with ac demand. My 86 Z kicks the clutch on without the ECM or any of it's wiring. My plan for the fan is to trip fan relay with a second relay grounding its signal, using the hot for the clutch as the signal for the second relay. Interested to see ideas on this as well. Only issue I see doing it this way is the fan will cycle with the clutch, which I believe should stay on constantly. I'm open to suggestions or corrections on a better way to do this.

QwkTrip

iTrader: (22)

Ah yes, good point about isolating the fan relay. This might bring the AC relay back in to play.

Lurbie

iTrader: (3)

This may be a stupid question, but why, with the HP system and its ability to control additional inputs and outputs, do you have to have this as a stand alone control? I thought it would accept an input like AC Request, and command an output to both the cooling fan relay and compressor relay along with bumping up your idle?

Restrorob

iTrader: (7)

Interesting thoughts Joe......



Here's another thought,

If the LT GRN wire from the head unit is tapped into before any of the pressure switches that should supply continuous power to a #2 fan relay, Now tap from #2 fan relay (LT GRN) to a second relay going to #1 fan AFTER the temp sensor relay.

In my case the temp sensor works on ground grounding the relay for #1 fan to operate as normal, With a second relay tapped into #1 fan after this temp sensor relay there shouldn't be any feedback power to this second relay to turn on #2 fan when the AC is off because this relay isn't activated.

Or am I all twisted around and missing something ?

Joe Tag

iTrader: (4)

Edited out the part about the diode. That was for another option I had now that I think about it. Was to reverse polarity on the fan relay and use a 2 pole temp switch. Wouldn't need the extra relay, just the diode to isolate the fan. Still kinda twisted myself, but I think you have it right Rob.

QwkTrip

iTrader: (22)

There are only 4 inputs and 4 outputs. That is a precious few and I don't want to consume them with AC controls.

QwkTrip

iTrader: (22)

I already have an underhood electrical center that I am installing. It has 2 fan relays and an AC relay pre-installed in the fuse center. The fan relays work on switch-to-ground of the field coil. The AC relay has loose wires for both sides of field coil so I can do whatever I want with that. Unfortunately, the AC relay is small and cannot power a fan or this would be really easy.

I came up with a few ideas with Holley HP, but I'm sure there is a better idea yet to be discovered.
Edit: Jump to post #38 for updated diagrams.

For you non-ECM guys, your AC relay can be a 3rd fan relay.

QwkTrip

iTrader: (22)

I just realized that I want to be able to turn off AC at wide open throttle. Back to the drawing board!

Joe Tag

iTrader: (4)

A little different than the way I had thought of doing it. But hot for the fan on diagram 3 should be before the High pressure switch and after the low, no?

Restrorob

iTrader: (7)

In my way of thinking, If you tap before either switch you don't have to worry about the fans shutting down when either low or high switch is tripped off. Therefore the fans will continuously run as long as the head switch is in AC position......

Joe Tag

iTrader: (4)

Pretty sure the low is just a safety feature for when refrigerant is leaked out so you don't trash a compressor. But it will work like that too.

QwkTrip

iTrader: (22)

I'm stuck at the moment. Posted at the Holley HP tech forum for help. I've used up a bunch of inputs and outputs and I'm not even sure if it can be programmed the way I want.

QwkTrip

iTrader: (22)

I have no idea. You probably know better than me.

I'm just throwing some ideas out to beat on. Improvements are welcome!

Joe Tag

iTrader: (4)

Well this is more along the lines of what I was thinking. Keeps the fan active and the extra relay is all low load circuit. Wish I could help you with the Holley system, but I have no experience with it.

Restrorob

iTrader: (7)

QwkTrip,


Could you not tie #2 fan relay to #1 relay which is activated by one output from your controller ? This is the low voltage circuit right ?

QwkTrip

iTrader: (22)

You could if you were willing to sacrifice having 2-stage cooling fans. I want to have one or both depending on conditions. Too much cooling in radiator can be a real problem in winter when the water pump thermostat isn't opening very often.

Joe Tag

iTrader: (4)

Can output for fan 2 be hot and have the relay already grounded? Then you can have the hot for compressor clutch kick the fan on like in my diagram or run direct from head unit and use a diode.
Edit: diode drawn wrong but you get the gist.

QwkTrip

iTrader: (22)

Found a problem with Option 1. AC clutch will not shut off because it is being fed by Fan 2 field coil so long as the high pressure switch is closed, which is pretty much whenever the AC compressor is running, right?

Joe Tag

iTrader: (4)

Option 1 of your diagrams is all messed up. You have the relay being grounded by ECM and connected to the hot for clutch. If you can run a hot for signal to the fan post 19 diagram should work.

QwkTrip

iTrader: (22)

Keep in mind with a switch to ground the field wire is always hot until the ECM grounds the terminal. Option 1 might work by moving the splice to location above the low pressure switch.

I redid your idea about hacking in to my fuse center and using the Fan 2 relay with high side switch (instead of low side switching). Is this what you envisioned?

Edit: Removed diagram. Go to post #38.

Joe Tag

iTrader: (4)

Yes, looks like it would work to me. If it makes it easier you can use high side switch on both fan relays.

QwkTrip

iTrader: (22)

Definitely one of the best ideas yet in this thread. Thanks for all your effort to help me!

I'm going to bake on this a little more. I'd really like to keep my fuse center in tact without hacking it up.

Joe Tag

iTrader: (4)

No problem, enjoyed the challenge. If you want to keep things as they are, you can add another relay and wire it to ground signal like the diagram in post 16.

QwkTrip

iTrader: (22)

I did a bit of learning and have a better understanding of how the pressure switches work and what they do. Option 1 just isn't going to work. I've deleted it to avoid further confusion.

Joe Tag

iTrader: (4)

This is probably a dumb Q and would be too simple, but are the outputs capable of closing the circuit under more than one circumstance? i.e. temp range and AC demand? I'm sure you would have thought of it if it were so, but I have to ask.

QwkTrip

iTrader: (22)

Yes, I am hoping so but I'm a novice with the HP system. That's basically the question I posted at the HP EFI forum.

QwkTrip

iTrader: (22)

Okay, this sucks. The HP drivers don't work like I thought they would. Every last idea I had for Holley HP won't work because I'm creating a short circuit on an ECM driver.

Back to square one. Glad I'm playing with paper and not real wires.

Restrorob

iTrader: (7)

I deleted my diagram as well to reduce confusion, I wish I was more help but not knowing anything about this Holley controller I'm in the dark.

But, Thanks for starting this thread for I now know exactly what I need to do to wire my fans for the ECU delete......

Joe Tag

iTrader: (4)

Sounds like you need to go old school on this. All of the functions for fans and A/C can be set up like Robs and mine with no ECM. For compressor cutout, maybe you can get a normally closed switch that mounts like a NOS switch for WOT. Just a thought.

Restrorob

iTrader: (7)

My thought on this is, The AC switch is just above the shifter..... You can reach up and flip it off in seconds, If some yayhoo pulls up next to you at a light and wants to play you've got plenty time to kill the AC.....

Joe Tag

iTrader: (4)

True, just tossing out an idea for hands free operation. I'm sure they make switches to mount for WOT application for NOS. Only issue is a NC switch.

Edit: Seems to not be an issue anyhow.
http://forums.holley.com/showthread....ng-with-HP-EFI
Check this one out too.
http://forums.holley.com/showthread....Fan-Holley-EFI

QwkTrip

iTrader: (22)

I found all that information too. I have questions about the hardware capability (ECM drivers) that I'm trying to sort out. I believe I have created short circuits in the ECM but don't know for sure until I know how the hardware behaves (not the software).

Joe Tag

iTrader: (4)

I'll tell you what I'd do.
"ASK OUR EXPERTS: 1-866-464-6553 "
You pay over 2k for a system, I'd expect some good technical support.

QwkTrip

iTrader: (22)

There is a mistake in the user manual that was the source of my worries. I've got the right info now and can continue.

QwkTrip

iTrader: (22)

The AC cutout isn't for the extra couple horse power, it's so you don't rev the **** out of the compressor at high rpm.

QwkTrip

iTrader: (22)

I think all these options can work. The missing options are ones that had problems and I'm not sharing. I need to sort out a few other things I want to control and see if I have the I/O left to do it.

Dual fan control, with and without AC. No AC relay needed. Downside is it has no AC shutoff at WOT.

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All the bells and whistles. Downside is it uses up 3 of 4 custom Outputs available on the Holley HP system, and I would have to hack into my fuse panel to rewire the Fan 2 relay so it operates on 12V switching.

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Same function as Option 4 but I don't have to hack my fuse panel and wiring is a bit more simplified. Still uses up 3 of 4 outputs from Holley HP system.

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Same basic function as Option 4 and 5 while using one less Input driver (thanks for the idea, Joe Tag), but loses the ability to turn off Fan 2 at will. Options 4 and 5 could shut off fans for any reason I want.

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Full featured but with safety improvement. AC request is visible to Holley ECM even if system goes over pressure and the high pressure switch opens. Fans will continue to run.