A/C request Blue/Green connector ECU
09-05-2018, 07:01 PM
#101
I think most of the confusion arose from the desire to eliminate the pin 80 pressure sensor from the system (notice I don't have it in my diagram above). If I understand correctly autocomman, you're saying that you have to have this sensor intact to use the truck ECM/flash? Or is it just necessary if you want certain features?
12-29-2018, 10:53 AM
#103
Ok, so I'm back at this again..... What I have now is a 2004 Silverado 6.0, and rewired the A/C back to the way it was originally in the '04 with the three wire pressure sensor. I added the wire for the 12v A/C request and just want to know what exactly to set the parameters to in the tune. I know it was serial originally, and need to change it to analog, but is it "analog cycling"? Basically all I want to do is add the 12v request to an '04 Silverado.
05-15-2019, 01:28 PM
#104
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So I've read this entire thread due to the problem I currently have. I have an 04 suburban 5.3 and 4l60e swapped into a 91 suburban with vintage air. I'm using the factory 3 wire pressure sensor, everything is wired right and I'm getting the 12v ac request at green 17 verified with a test light. I can use hptuners vcm scanner to command the AC compressor on through the pcm, when I do the AC blows cold and the cooling fans come on when the pressure threshold is reached. My PCM is service number 12586242. I've come to understand that it is simply not capable of accepting the 12v request. Here's my dilemma: I have HP tuners and don't want to waste credits trying to find a PCM that will control my fans and AC while being DBW. Can anyone tell me a PCM service number that they know will accomplish this?
05-15-2019, 02:06 PM
#105
TECH Senior Member
You might try contacting LSX Power Tuning. Not positive they would know, but it's worth a shot. They are of a lot of help on this forum.
01-17-2021, 07:07 PM
#106
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Dcon (07-19-2021)
08-30-2021, 06:02 PM
#107
Have you actually solder these in place to see if it work? I messed around all day trying different thing to get mine to work and come across this, I have already order the resistor and capacitor to try, but have you gotten it to work?
08-30-2021, 06:49 PM
#108
TECH Senior Member
08-30-2021, 07:36 PM
#109
Skylerm09- yes, I did solder these elements (2 resistors and a capacitor) into the motherboard, and the changes worked. I was able to show this with a bench-top experiment (see document attached). Providing 12 volts to C2 17 in the PCM resulted in the voltage at C2 43 going low, which is an indication that the PCM is trying to command the AC compressor to come on.
Note that to get this to work on the benchtop, you have to simulate the crank and cam signals, which I did with a arduino and the ardustim c-code software found online which I modified for my own use.
I was also able to get the 2 fan controls to cycle on and off by simulating the engine coolant temperatures with a potentiometer.
So all these functions were working in a PCM that did not originally work.
Note that to get this to work on the benchtop, you have to simulate the crank and cam signals, which I did with a arduino and the ardustim c-code software found online which I modified for my own use.
I was also able to get the 2 fan controls to cycle on and off by simulating the engine coolant temperatures with a potentiometer.
So all these functions were working in a PCM that did not originally work.
08-30-2021, 08:12 PM
#110
Can you give me exact on the capacitor? I order 100,10, 3. kOhm resistor I didn’t really understand what you were saying, I’m no professional or even a novice at this but I seen you picture and I’m good with a iron. So I wanna give it a shot before I spend 100$ on credits and 50 on a pcm.
09-01-2021, 01:16 AM
#118
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Hope this is not duplicate post? (Last message had attachment image, not allowed for beginners?)
This is how I wired A/C, now FAN(s) are on when A/C is on.
Edit: without pressure sensor.
https://universalpatcher.net/wp-cont...ensor-Fans.png
Compressor type: Analog.
Maybe gnd to pin 55 is not required?
This is how I wired A/C, now FAN(s) are on when A/C is on.
Edit: without pressure sensor.
https://universalpatcher.net/wp-cont...ensor-Fans.png
Compressor type: Analog.
Maybe gnd to pin 55 is not required?
Last edited by Jouko Y; 09-03-2021 at 06:11 AM.
09-02-2021, 05:57 PM
#119
The HVAC module communicates by the GM class-2 serial protocol used at that time. It's a digital signal, not analog. I used the HVAC module as a baseline test. I wanted to confirm first that the PCM would operate as expected as it arrived from GM. Because the donor vehicle for the PCM was a 2004 Silverado or Sierra, the way the AC system was controlled from the factory was with that module. So before I modified the PCM, I wanted to verify that I could correctly interpret the response of the PCM when AC was requested through the HVAC module. This was a confirmation that my bench-top setup was correctly wired up and working properly.
Once that was done, I could then proceed to modify the PCM, and try to activate AC with just a 12 Volt signal. Which was also successful, but only after I implemented the fix to the motherboard. Before that, only the HVAC module would activate AC. Now, I can program the PCM to accept either a serial data or analog AC request.
Once that was done, I could then proceed to modify the PCM, and try to activate AC with just a 12 Volt signal. Which was also successful, but only after I implemented the fix to the motherboard. Before that, only the HVAC module would activate AC. Now, I can program the PCM to accept either a serial data or analog AC request.
09-02-2021, 07:27 PM
#120
The HVAC module communicates by the GM class-2 serial protocol used at that time. It's a digital signal, not analog. I used the HVAC module as a baseline test. I wanted to confirm first that the PCM would operate as expected as it arrived from GM. Because the donor vehicle for the PCM was a 2004 Silverado or Sierra, the way the AC system was controlled from the factory was with that module. So before I modified the PCM, I wanted to verify that I could correctly interpret the response of the PCM when AC was requested through the HVAC module. This was a confirmation that my bench-top setup was correctly wired up and working properly.
Once that was done, I could then proceed to modify the PCM, and try to activate AC with just a 12 Volt signal. Which was also successful, but only after I implemented the fix to the motherboard. Before that, only the HVAC module would activate AC. Now, I can program the PCM to accept either a serial data or analog AC request.
Once that was done, I could then proceed to modify the PCM, and try to activate AC with just a 12 Volt signal. Which was also successful, but only after I implemented the fix to the motherboard. Before that, only the HVAC module would activate AC. Now, I can program the PCM to accept either a serial data or analog AC request.
never ceases to amaze me how smart some guys on here are... thanks for sharing this, i'm sure this will be helpful to lots of people
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G Atsma (09-02-2021)