Vintage Air with LS Swap - non-pcm control strategy

[NC_John]

I'm at the final stages of my ls swap and trying to finish up my vintage air control strategy. I am specifically trying to sort out how to disable the compressor on both wide open throttle and/or a predetermined high rpm setpoint. Vintage air does not include these functions in their very limited controls and like most vintage air users, I am controlling it independent of the pcm.

I can't seem to find an output(s) on the pcm that is/are activated by either of those conditions so it appears I need to do it externally. (I did run a spare wire along with the pcm harness in case there is a signal I can use).

For the wide-open throttle disable I found this from Nitrous Express. I can simply use the provided relay in series with the compressor contol signal to cut it off on wide open throttle.

http://www.nitrousexpress.com/oldweb..._autolearn.pdf

Any ideas on how I can get the high rpm limit disable set up? Maybe through a shift light style logic?

[Clyde65]

The AC should be hooked up as stand alone. I have the Old Air Products and use a tri-nary switch to run the 2nd fan.

[Wildkarde]

Autometer makes some RPM activated switches that should get you the ability to trigger a relay above a certain rpm.

I thought about all that, but decided it wasnt worth the hassle and complexity just so I didnt have to remember to shut the AC off when I was making a run.

[sprint_9]

What generation of PCM do you have, gen 3 or 4? I was thinking my Gen 4 had something like what you wanted, I know under the program in HP tuners there is an RPM and TPS option to disable the AC. I had hoped to use this on mine but haven't gotten that far into it yet.

If running through the PCM isnt an option I will most likely go with something like what is shown in this manual from Holley. http://documents.holley.com/199r11334.pdf

[Wildkarde]

They all have that option in the ecm, just that from 2003 on theres no output for turning the compressor on and off in the ecm, its handled by the BCM through the data link.

[NC_John]

Originally Posted by sprint_9

What generation of PCM do you have, gen 3 or 4? I was thinking my Gen 4 had something like what you wanted, I know under the program in HP tuners there is an RPM and TPS option to disable the AC. I had hoped to use this on mine but haven't gotten that far into it yet.

If running through the PCM isnt an option I will most likely go with something like what is shown in this manual from Holley. http://documents.holley.com/199r11334.pdf

Originally Posted by Wildkarde

They all have that option in the ecm, just that from 2003 on theres no output for turning the compressor on and off in the ecm, its handled by the BCM through the data link.

Its an 04 truck pcm, blue/green. I know the pcm has the output but don't know if it works when the AC is controlled externally (like through VA). If the output is in the pcm for high rpm/wot cutoff, but the AC command is actually triggered by the bcm, does the pcm disable output work regardless of whether or not AC is on? If so, that would work. Need to figure that out.

[NC_John]

Originally Posted by Wildkarde

Autometer makes some RPM activated switches that should get you the ability to trigger a relay above a certain rpm.

I thought about all that, but decided it wasnt worth the hassle and complexity just so I didnt have to remember to shut the AC off when I was making a run.

Will check that out.

I want it to function like the factory setup, for spur-of-the-moment shenanigans.

[ls1nova71]

Originally Posted by NC_John

Its an 04 truck pcm, blue/green. I know the pcm has the output but don't know if it works when the AC is controlled externally (like through VA). If the output is in the pcm for high rpm/wot cutoff, but the AC command is actually triggered by the bcm, does the pcm disable output work regardless of whether or not AC is on? If so, that would work. Need to figure that out.

The A/C isn't controlled by the BCM in an '04. It's controlled by the HVAC switch, which is a module that communicates with the PCM via the serial data line, hence, there is no dedicated 12v A/C request wire. You can kind of get around it though, but it's not perfect. What you can do is find a blue/green PCM that has IAC drivers in it, add the 12v request wire, then have the tune changed to make it work. If I remember correctly, you need to change it from serial request to analog cycling. This would allow you to control the compressor through the PCM. What it wont do though is run the electric fans, you will need the VA trinary switch for that. What is the service number on your PCM? I'm going to make a wild guess that its 12586242, but if it's 12586243 then that's the PCM you want. There are others that will work, but these are specifically 2004's.

[NC_John]

Originally Posted by ls1nova71

What you can do is find a blue/green PCM that has IAC drivers in it, add the 12v request wire, then have the tune changed to make it work. If I remember correctly, you need to change it from serial request to analog cycling. This would allow you to control the compressor through the PCM. What it wont do though is run the electric fans, you will need the VA trinary switch for that. What is the service number on your PCM? I'm going to make a wild guess that its 12586242, but if it's 12586243 then that's the PCM you want. There are others that will work, but these are specifically 2004's.

Ahhhh... the man I was hoping to hear from!

Well, this PCM is already cracked by HPTuners and I sure don't want to buy another license and I'd really prefer to manage the on/off of the AC through the Vintage Air controls, just for simplicity.

LT1swap.com shows pin 14 as A/C Refrigerant Pressure Sensor and pin 43 as the AC compressor clutch relay control on the green harness. 43 must incorporate the logic for WOT and high RPM cutoff. I wonder how to enable that output works regardless of whether or not the PCM is actually controlling the AC compressor. How can I force the PCM to always send an AC compressor request as an output but just use it to drive the relay that goes in series with the Vintage Air compressor signal.

Might just be easier to go the external NX and Holley switch route.

Think I can see any of this through a tech II ? I don't know if HPTuners will go that in depth (and I don't personally own that software). I'll check the service number this afternoon/evening.

thanks

[NC_John]

Originally Posted by sprint_9

If running through the PCM isnt an option I will most likely go with something like what is shown in this manual from Holley. http://documents.holley.com/199r11334.pdf

Oh hell, that switch is $175 from summit! Yikes.

[sprint_9]

Originally Posted by NC_John

Oh hell, that switch is $175 from summit! Yikes.

I saw a couple cheaper ones that might work. I agree, that NOS switch seems expensive.

https://www.summitracing.com/search/...PM%20Activated.

[NC_John]

Originally Posted by ls1nova71

What is the service number on your PCM? I'm going to make a wild guess that its 12586242, but if it's 12586243 then that's the PCM you want. There are others that will work, but these are specifically 2004's.

I've got a 12586242. Doing more research and it might just be easiest, if not the least expensive, to do the external switches/relays and just keep the pcm out of it. Of course, if I have idle speed issues when the compressor kicks on, that might change my thinking.

[ls1nova71]

Originally Posted by NC_John

LT1swap.com shows pin 14 as A/C Refrigerant Pressure Sensor and pin 43 as the AC compressor clutch relay control on the green harness. 43 must incorporate the logic for WOT and high RPM cutoff. I wonder how to enable that output works regardless of whether or not the PCM is actually controlling the AC compressor. How can I force the PCM to always send an AC compressor request as an output but just use it to drive the relay that goes in series with the Vintage Air compressor signal.

Think I can see any of this through a tech II ?

Pin 43 does control the compressor clutch, but it's the PCM that controls pin 43. The PCM knows throttle position percentage and engine RPM and commands the clutch on and off by these and other inputs. I don't think you are going to be able to force the PCM to send the request as a hard wired output, at least not with the PCM you have. You can see some parameters with a TechII, but nothing that is really going to help you in your situation.

Originally Posted by NC_John

I've got a 12586242. Doing more research and it might just be easiest, if not the least expensive, to do the external switches/relays and just keep the pcm out of it. Of course, if I have idle speed issues when the compressor kicks on, that might change my thinking.

This is probably your best bet if you can find one module that does both throttle position and RPM in one package, I would do that. The DBW throttle body should be more than able to compensate for the additional load placed on the engine by the A/C compressor.

[davepl]

TPS Switch and RPM switch, both of which are available from NX, would seem to do the trick.

A simple mechanical contactor for the idle would be simpler though! Like a WOT switch but wired for idle.

[NC_John]

Originally Posted by davepl

TPS Switch and RPM switch, both of which are available from NX, would seem to do the trick.

A simple mechanical contactor for the idle would be simpler though! Like a WOT switch but wired for idle.

I'm not sure what you mean with controlling it by the idle. 'Splain please!

[davepl]

If I understand you need to know two things:

1) When you're at idle
2) When you're above a certain RPM

(2) Can be done with a nitrous window switch. It connects when RPM is greater than some amount.

(1) Can be done with either a mechancial WOT switch set up at idle rather than WOT, or a TPS window switch.

The TPS Window switch (like part # NX 19859) monitors the 0-5V signal coming from the TPS and and then connects when the TPS is above or below a certain value. Your worst case here is that it works backwards from what you want (connects at idle and you want connected at NOT idle) and then you could use a relay to NOT the signal, but I'd check the manual for the switch.

So the WHITE wire from the NX switch goes to the TPS wire on the throttle body. Grey to RPM.

Then you go in and set where your RPM windows are and what to do when you hit them as per the manual here:

http://www.nitrousexpress.com/oldweb...ndowswitch.pdf

It's -possible- you can do the whole thing with just this switch and a relay, but I haven't thought it through that far!

[NC_John]

Originally Posted by davepl

If I understand you need to know two things:

1) When you're at idle
2) When you're above a certain RPM

........

http://www.nitrousexpress.com/oldweb...ndowswitch.pdf

It's -possible- you can do the whole thing with just this switch and a relay, but I haven't thought it through that far!

Actually the two conditions when you want to disengage the AC compressor are wide open throttle (not idle) and at a certain rpm and above (as prescribed by Sanden or compressor manufacturer - they do provide that spec).

So it sounds like we are talking about doing the same thing- you just might have found a switch that will allow me to monitor both functions in one. I'll take a look at it.

[NC_John]

yeah Dave, it looks like that switch will do both functions with the one module. $195 from Summit so still not cheap but less expensive than using two different modules.

thanks!

[davepl]

Happy to help, hope it does what you need!

There are a lot of little "circuits" on Amazon too. I bought one to do theatre style dimming of the interior lights, for example. Just they can be hard to find with search!