A/C request Blue/Green connector ECU
#1
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Ok, maybe we can get this in a sticky with the correct info. ive got an LQ4 from a 2004 truck, its got the blue/green connector ECU. This one is a DBW and normally used the HVAC headunit to control the compressor via serial data through the ECU. We all know that the usually tuners can change this to a simple 12v A/C request, and a variable/fixed compressor etc etc.
So the question is, what pins have to be changed on the ECU for
1. A/C request,
2. Compressor clutch control, and
3. Pressure sensor, and what sensor to use.
There is a lot of stuff out there for the red/blue connector ecu, but a lot of scattered info for the blue/green Lets see if we can get it all in one place. For both the red/blue and blue/green ECU's and have it easily acessible. Hard fast simple answer, this is what goes where
So the question is, what pins have to be changed on the ECU for
1. A/C request,
2. Compressor clutch control, and
3. Pressure sensor, and what sensor to use.
There is a lot of stuff out there for the red/blue connector ecu, but a lot of scattered info for the blue/green Lets see if we can get it all in one place. For both the red/blue and blue/green ECU's and have it easily acessible. Hard fast simple answer, this is what goes where
#4
TECH Enthusiast
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If you want to use a variable compressor wire it like a 02 Camaro. If you want a fixed compressor wire it like a Express van. Both use a 12 volt A/C request. The programming portion only sets the A/C type. Also note that you can use a variable compressor on anything. The difference is a wiring and either a pressure sensor or switch.
#5
TECH Apprentice
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If you want to use a variable compressor wire it like a 02 Camaro. If you want a fixed compressor wire it like a Express van. Both use a 12 volt A/C request. The programming portion only sets the A/C type. Also note that you can use a variable compressor on anything. The difference is a wiring and either a pressure sensor or switch.
#6
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Wire the sensor like a van then? And get a sensor from a van? is that a binary (only low or high pressure) or trinary (both high and low) switch? Or is it a variable sensor.
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#8
TECH Apprentice
iTrader: (21)
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I've heard bp automotive can make the 12v request and the pressure sensor work together. I own hptuners and built my own harness, so I'd like to figure out how we can do this on our own.
#9
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Ok so then this diagram is for an 02 Fbody, this cannot be used with a fixed compressor? Because ive seen people do it, there is even a thread or 2 in here that used this. If you wanted fan control can you do it this way?
THe second diagram is the express setup, very simple. High pressure cutout inline with the A/C request. Compressor clutch control, and the low pressure switch looks like its a ground signal for cycling control.
With that said, what in HP tuners gets changed. Is it that obvious? Im gettin my ECU flashed tonight at a buddys house and Id like to have that all straightened away.
2002 F-body
![Name: 2002fbodycompressorcntrl_zps634a112d.gif
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2004 EXPRESS VAN
THe second diagram is the express setup, very simple. High pressure cutout inline with the A/C request. Compressor clutch control, and the low pressure switch looks like its a ground signal for cycling control.
With that said, what in HP tuners gets changed. Is it that obvious? Im gettin my ECU flashed tonight at a buddys house and Id like to have that all straightened away.
2002 F-body
![Name: 2002fbodycompressorcntrl_zps634a112d.gif
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Size: 96.6 KB](https://ls1tech.com/forums/attachments/conversions-swaps/606342d1501313852-c-request-blue-green-connector-ecu-2002fbodycompressorcntrl_zps634a112d.gif)
2004 EXPRESS VAN
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Last edited by autocomman; 07-23-2014 at 11:36 AM.
#11
TECH Enthusiast
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If the OS does not have 2 fans then you have to program it for 2 fans and wire it again like an 02 Camaro or a similar 2 fan setup. All 411 and Red/Green wiring is basically the same minus variations in configurations such as O2 sensors, fans, A/C, etc. All can be programmed to function like something else or a different OS can be used. If you at using a cable a 04 GTO or 05 Express van is a good start. If you are using DBW then a 04 Vette or 05 CTSV is a good start for car tunes. It is the combination of the 2 -wiring and OS programming that gets you what you want.
#15
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Perhaps it was my misunderstanding, but I thought the 01 Fbody AC unit sent a ground signal to the PCM C2, pin 17, but what I read here, the AC unit sends a +12V signal. Can someone please set me straight; is it ground, or is it +12V to C2, 17?
Thanks,
Andy1
Thanks,
Andy1
#16
TECH Enthusiast
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I want to make sure I understand this, the 04 express van calibration uses a 12v signal for the AC request? But the express van calibration won't control the fans?
Perhaps it was my misunderstanding, but I thought the 01 Fbody AC unit sent a ground signal to the PCM C2, pin 17, but what I read here, the AC unit sends a +12V signal. Can someone please set me straight; is it ground, or is it +12V to C2, 17?
Thanks,
Thanks,
#17
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Hi All this is a great topic I'm working on the same problem.
I've come up with these solutions for Blue/Green Connectors
On the left would require reprogramming with HPTuners not sure this is possible anybody can give me some input on this?
The option on the right would make the AC work independently not sure if it would affect the engine performance.
Thanks!
I've come up with these solutions for Blue/Green Connectors
On the left would require reprogramming with HPTuners not sure this is possible anybody can give me some input on this?
The option on the right would make the AC work independently not sure if it would affect the engine performance.
Thanks!
Last edited by kleyba; 08-11-2014 at 09:53 AM.
#18
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Some poeple say when you dont tel the ECU the A/C is on their car runs fine. Really though with the A/C request hooked up properly, at near WOT the A/C kicks out, you can also set it to turn off over a certain RPM, the ECU also ups the idle, and can control fans if need be...so reconfiguring the ECU and hooking up proper A/C request and compressor control is the correct way to do it, but guys have gone around that.
#19
10 Second Club
iTrader: (19)
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Sorry to dig up such an old thread but I'm having issues getting the IAC to respond to the request signal on a swapped car. The OS is a 2001 suburban, its in an 89 caprice. I have the 12V signal coming from the pressure switch/sensor & have verified voltage to pin 17 but still the computer acts like it doesn't recognize the request signal. The compressor is set to analog cycling, does this need to be changed?
I'm not trying to operate the fans or anything fancy, just keep the car running when the ac is engaged.
Edit: I didn't ground C2 pin 55, is this needed?
I'm not trying to operate the fans or anything fancy, just keep the car running when the ac is engaged.
Edit: I didn't ground C2 pin 55, is this needed?
Last edited by WS6HUMMER; 08-06-2015 at 02:08 PM.
#20
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Im wondering that same thing WS6hummer, i finally got to the ac this weekend. Got the request hooked up properly, verified A/C request on a scanner, but it wont turn the relay on. I have the pressure sensor hooked up and it was a hot day, 111 psi, should be more nad sufficent to kick the compressor on, but wouldnt do it. Its a stock 03 silverado 6.0 OS, but with electric fans enabled and analog compressor control fixed compressor etc etc. Does the low pressure switch wire need to be grounded? on pin 55??
Mark
Mark