AEM v2 6100 A/C signal from amplifier | AEM
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turbogate
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AEM v2 6100 A/C signal from amplifier

Hey guys, quick question.  Pin 34A (input) on the 6100 box expects which signal? ground or positive?  I'm have a ground signal to send to ecu to idle up/compensate for A/C compressor load when it kicks-in (6100 box on MKIII 2JZ Supra).  I figured I would use the default pin.

Thanks,

AEM_NS
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34A is an analog input that

34A is an analog input that should only receive a 0-5v or ground signal. Sending 12v into this pin could damage the hardware.

turbogate
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Thanks, glad i asked.  The

Thanks, glad i asked.  The signal I have to send is a ground signal, if I choose another available switch input, let's say switch 6 (pin 4A) and send a ground to it, can I select that as the input for the A/C Switch input option to have the AEM adjust the idle to compensate for the a/c compressor load when the A/C kicks in?  

Thanks again,

AEM_NS
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Check the available inputs

Check the available inputs for the A/C Switch Input (under Idle tab) option to see what inputs are available.

Kurt
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There is a difference in the

There is a difference in the way the MKiii and MKIV control the a/c compressor clutch.  

In the MKIV, the a/c amplifier is looking at the dual pressure switch and all the other climate control sensors and will send the signal to pin 34a when it decides the clutch should be engaged.  From there, the ecu decide if conditions are ok to engage the clutch (rpm, thorttle).  So, the stock ecu, or AEM EMS is told to activate the a/c clutch but it doesn't have to do it right at that moment.  This allows for a delay and increase idle % to compensate for the added load so rpm doesn't drop.  This arrangement allows for the control you're wanting to implement.

Pin 34A on the 6100 is a 0-5v analog input, as opposed to a switch input.  Switch inputs (#2-#6 are available) have a 12v pull-up and are intended to have the wire either go to nothing or go to ground.  What the AEM sees on these inputs is either 12v or 0v... On or Off.  I don't think the MKIV a/c amplifier completely grounds the request signal to 34a, so that's why it needs to use an analog voltage input to see when the request is made.  There are two "software switches" in the V2 called switch 7 and switch 8.  These software switches have options that allow an analog voltage threshold (and also rpm and tps criteria) to create a "switch" that is either on or off.  If the MKIV a/c amplifier pulled that wire completely to ground, then one of the regular switch inputs would work, but that's not the case.  Look through the 6100 startup cal and you'll see it uses switch 7 as the a/c request input.

I haven't looked too deeply into the workings of the MKiii a/c system, but from the diagrams it looks like the clutch is operated directly by the dual pressure switch or maybe by the a/c amplifier.  Not by the ecu like the MKIV does so no delay and idle % increase. Pin 7 at the a/c amplifier (brown wire) goes to the clutch relay.  This works either of two ways which you will want to investigate.  1: It gives a constant ground when you press the a/c button and the dual pressure switch is alone responsible for turning the a/c clutch on and off.  Or, 2:  the a/c amplifier is looking at the signal from the dual pressure switch and then controls the clutch through pin 7.  In case 2, it's possible you could divert that signal to a spare switch input on the AEM and wire a spare LS out to the a/c clutch relay.  This would allow the AEM to control the clutch and allow for a delay and idle % increase each time the a/c amplifier asks for the clutch to engage.  If it's case 1 then it complicates things and you'd have to get more creative.  

turbogate
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Thanks Kurt for the detailed

Thanks Kurt for the detailed explanation.  My A/C is already working as expected; in the MKIII the A/C compressor is controlled by the A/C control panel through the amplifier.  Almost like the MKIV, but without going through the ECU at all.  What i'm trying to do is send a ground signal to the ECU (A/C request input?) to compensate for the compressor load and adjust the idle when it engages/dissengages as the the climate control turns the compressor ON and OFF based on the climate control sensors.

Below is what I'm trying to do with the 6100 box but the below is for the MKIII 1130 box.

http://www.supramania.com/forums/showthread.php?50143-Fixing-a-c-idle-up...

Thanks guys

 

Kurt
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So, pin 11 on the a/c amp is

So, pin 11 on the a/c amp is a ground switch that goes to a regular switch input on the AEM (#2-#6).  The problem with this is that it won't turn on and off with with the compressor clutch, it's just "on" when the a/c is on.  The person in your link makes an important point about the idle learned value and how it can cause stalling after "winding down" to compensate for the inadequate signaling configuration.  I find it best to allow only -1.2% or as little as possible negative feedback range to avoid idle stalling issues. 

The solution in your link was to add a relay in the engine bay controlled by the a/c clutch relay.  This added relay sent a ground signal back to the AEM when the clutch is active.  But the a/c clutch control remains with either the dual pressure switch or pin 7 from the a/c amplifier.  You'll want to test this and find out which.  This solution provides an appropriate switch signal to give an idle up but does not allow for a delay in clutch activation to give the iacv time to actually move there before it.  Idle will likely drop down and oscillate each time.  

It will either be simple or only slightly less simple to give control of the a/c clutch to the AEM.  Either case will involve running that brown wire from the a/c clutch relay back to a spare LS output on the AEM.  Cut it at the a/c amp plug so it's no longer connected to pin 7.  If the a/c amp works by monitoring pin 12 for 12v from the dual pressure switch and then grounds pin 7 on/off to control the clutch then you can simply wire pin 7 to a regular switch input on the AEM and you will have your switch signal request for a/c clutch.

If pin 7 is simply always ON (ground) when you press the a/c button then that means it's just the dual pressure switch that controls the clutch.  You can do what was suggested in your SM link and control an extra relay with the 12v from the dual pressure switch and send a ground switch signal to the AEM.  Just do this on the wires at the a/c amp so you don't have to run anything from the engine bay.

 

turbogate
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As always you are the man

As always you are the man Kurt, thanks for taking the time to write all of this.  It is truly appreciated.

JesLet
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Joined: 06/23/2015 - 23:08
Kurt wrote:

Kurt wrote:

There is a difference in the way the MKiii and MKIV control the a/c compressor clutch.  

In the MKIV, the a/c amplifier is looking at the dual pressure switch and all the other climate control sensors and will send the signal to pin 34a when it decides the clutch should be engaged.  From there, the ecu decide if conditions are ok to engage the clutch (rpm, thorttle).  So, the stock ecu, or AEM EMS is told to activate the a/c clutch but it doesn't have to do it right at that moment.  This allows for a delay and increase idle % to compensate for the added load so rpm doesn't drop.  This arrangement allows for the control you're wanting to implement.

Pin 34A on the 6100 is a 0-5v analog input, as opposed to a switch input.  Switch inputs (#2-#6 are available) have a 12v pull-up and are intended to have the wire either go to nothing or go to ground.  What the AEM sees on these inputs is either 12v or 0v... On or Off.  I don't think the MKIV a/c amplifier completely grounds the request signal to 34a, so that's why it needs to use an analog voltage input to see when the request is made.  There are two "software switches" in the V2 called switch 7 and switch 8.  These software switches have options that allow an analog voltage threshold (and also rpm and tps criteria) to create a "switch" that is either on or off.  If the MKIV a/c amplifier pulled that wire completely to ground, then one of the regular switch inputs would work, but that's not the case.  Look through the 6100 startup cal and you'll see it uses switch 7 as the a/c request input.

I haven't looked too deeply into the workings of the MKiii a/c system, but from the diagrams it looks like the clutch is operated directly by the dual pressure switch or maybe by the a/c amplifier.  Not by the ecu like the MKIV does so no delay and idle % increase. Pin 7 at the a/c amplifier (brown wire) goes to the clutch relay.  This works either of two ways which you will want to investigate.  1: It gives a constant ground when you press the a/c button and the dual pressure switch is alone responsible for turning the a/c clutch on and off.  Or, 2:  the a/c amplifier is looking at the signal from the dual pressure switch and then controls the clutch through pin 7.  In case 2, it's possible you could divert that signal to a spare switch input on the AEM and wire a spare LS out to the a/c clutch relay.  This would allow the AEM to control the clutch and allow for a delay and idle % increase each time the a/c amplifier asks for the clutch to engage.  If it's case 1 then it complicates things and you'd have to get more creative.  

 

Hello Kurt,

I am very slow at this i hope you can help. I have a 1995 Supra NA with 2jzgte non vvti swap and using am AEM V2 6100. A friend told me i need to do a relay setup in order to run my A/C from the AEM V2.

Can you please tell me where pins 87 and 86 on the relay go to ?  (85 is ground and 30 is 12+ battery)

I found teh wiring diagram for 1995 Supra and you can see on pages 230 and 231

http://shoarmateam.nl/upload/MKIVSupra/Supra-MKIV-Repair-Manual/Wiring%20Diagrams.pdf

 

Thank you