A/C request Blue/Green connector ECU
08-17-2015, 11:31 PM
#21
On The Tree
Thread Starter
Join Date: Aug 2013
Posts: 188
Likes: 0
Received 0 Likes
on
0 Posts
Anyone? I understand you can change options within the OS, but fan control, analog request and fixed cycling compressor, do i need the low pressure switch input to make it come on?
08-19-2015, 11:11 AM
#22
Yes it is, back when I was putting the A/C in my el camino (2001 red/blue tahoe operating system) all I had to do was ground pin 55 (right to ground, no switch needed) and then I hooked pin 17 to my a/c clutch power wire. As soon as the compressor turned on the idle would kick up and the fans would kick on. But without grounding pin 55 the computer will not kick up the idle or actuate fans.
Further info for this thread:
Oddly enough, years later I realized that my fan turn on points are based on A/C pressure but I don`t have any type of A/C press sensor hooked into the pcm. Seeing that I am hopeful that maybe using a truck OS on the later blue/green pcm and wiring it with the 12v a/c request + grounding pin 55 may work for actuating the fans?? I have another car that I need to try this on but just have not had time yet. I will report back when I do.
Further info for this thread:
Oddly enough, years later I realized that my fan turn on points are based on A/C pressure but I don`t have any type of A/C press sensor hooked into the pcm. Seeing that I am hopeful that maybe using a truck OS on the later blue/green pcm and wiring it with the 12v a/c request + grounding pin 55 may work for actuating the fans?? I have another car that I need to try this on but just have not had time yet. I will report back when I do.
08-26-2015, 10:14 AM
#24
Teching In
Join Date: Jan 2014
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
analog or analog cycling? Hey guys do you know what the default tune is for 99-02 camaro if it is set to analog, or analog cycling? Reason I ask is I did an ls1 conversion into my thirdgen camaro, and used a standalone PSI conversion harness with no AC provisions. Pocket - a member here and on thirdgen.org built a 4th gen harness to use on my car with the ls1 compressor, and connecting to my factory harness for AC, and pins on the computer (Red/Blue) that had to be added. It was plug and play but when I turn my ac on the compressor doesn't start, and I can manually jumper the relay and it kicks on. So I am thinking maybe its my tune setting? Its currently set for Analog, and the hptuners OS is for a 4th gen camaro 5.7L. Any help would be appreciated.
08-29-2015, 11:51 AM
#25
I believe that the 99-02 is usually set to analog from the factory, I pulled a couple files and they were all set to analog which makes sense. As the 99-02 used a 12v trigger so it should be analog and it was not a cycling system.
Are you using a pressure transducer from a 99-02 f-body? That system will not work with a low/high pressure switch, it has to be the pressure sensor.
Are you using a pressure transducer from a 99-02 f-body? That system will not work with a low/high pressure switch, it has to be the pressure sensor.
08-30-2015, 05:32 PM
#26
Teching In
Join Date: Jan 2014
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
I am using a pressure sensor for a 90 grand am three pin, as advised from thirdgen.org forum. ACDelco part 15-72104. It is wired correctly and using my multimeter, I am getting correct voltage on all the PCM's ac wiring. The only thing in question right now is the Red/Black wire on the pressure switch C2 pin 14, circuit 380. I register 4.2v there, and I believe that is too high for it to turn the compressor on.
I start the car with the AC turned on, and the fans immediately come on, but I don't hear the AC compressor engage. I have taken the pressure sensor pigtail loose, and the fans immediately go off, and I am almost sure I hear the AC compressor click like its either engaging or disengaging.
I have ordered another pressure sensor to see if maybe I have a bad one, I have read 2-2.5 volts is where it should operate. My ac tech that filled it with R134 swears it is filled correctly and the system shouldn't be over pressure - which is what the 4.5v sounds like to me.
I still have the third gen cycling switch hooked up, but from studying the 02 LS1 AC wiring diagram its not even being used. Should I unplug this?
I start the car with the AC turned on, and the fans immediately come on, but I don't hear the AC compressor engage. I have taken the pressure sensor pigtail loose, and the fans immediately go off, and I am almost sure I hear the AC compressor click like its either engaging or disengaging.
I have ordered another pressure sensor to see if maybe I have a bad one, I have read 2-2.5 volts is where it should operate. My ac tech that filled it with R134 swears it is filled correctly and the system shouldn't be over pressure - which is what the 4.5v sounds like to me.
I still have the third gen cycling switch hooked up, but from studying the 02 LS1 AC wiring diagram its not even being used. Should I unplug this?
08-30-2015, 06:44 PM
#27
Teching In
Join Date: Jan 2014
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
It also appears that GRN/WHT going to relay control on PCM pin C2 - 43 is putting out 12+ volts, rather than seeing the ground that I am expecting. When I manually ground the relay on that pin the compressor clutch clicks and engages.
08-31-2015, 02:21 PM
#28
Yep, that sounds like its over pressure. But that pressure sensor is not the correct one for a 02 f-body which may be the problem. It looks like the 1994-2001 grand am uses the same sensor as the 02 f-body but the 1990 is different. Try putting a 80k ohm resistor between red/blk and gray wire. That should get you about 2v and then both the fans and compressor should kick in.
09-01-2015, 02:08 PM
#29
Well after spending hours playing with HPTuners and a tech 2 I have found that the A/C request switch feature only partially works. You don`t have as much capability to change the A/C request type as the options in HPTuners would lead you to believe.
I`m working with a 2003 blue/green pcm # 12576106 operating system # 12579405. This PCM and OS were used in both trucks/suv`s and vans with serial (trucks/suv`s) and analog cycling (vans) a/c request types. Since this PCM and OS was used both with the pressure switch and sensors and as a serial or analog cycling request I thought that I would be able to simply change my request type from serial to analog cycling, ground C2 pin 55, give +12v to C2 pin 17, and get the pcm to bump my idle and turn the fans on.
Turns out the PCM would acknowledge the A/C request but would not bump the idle, energize the a/c relay or fans as it was looking for the pressure sensor signal not the ground from the low pressure switch. I was kinda pissed but realized this OS was also used in the vans....so I changed my platform type to GMT610. This did not work as it was still looking for the pressure sensor. I really don`t understand why as this OS was used in both trucks and vans. So I changed back to the GMT800 platform and added 2 100K resistors in parallel (I didn`t have any resistors between 47k and 100k on hand so the 2 paralleled 100`s make approx 50k) in place of the pressure sensor. Now I had the PCM accepting an 12v a/c request and the PCM was seeing ~228psi of pressure but it still would not bump the idle, trigger the clutch relay or the fans. I tried using the tech 2 to manually enable the clutch relay but it told me the A/C pressure was out of normal range. I tried using different resistors and varied the a/c pressure between 91 and 372 psi but nothing worked and the tech 2 always said the a/c pressure was out of range if I tried to enable the relay manually.
Finally I changed my a/c request type to analog. That fixed most of the issues. Now with +12v to C2 pin 17 and the 2 100k parallel resistors between pin C1 45 and C2 pin 14 the PCM would trigger the a/c clutch relay and the idle would bump up. I still am not able to trigger the fans no matter where I set the fan 1/2 enable A/C pressure, but I know this truck had a mechanical fan from the factory so maybe it is impossible to trigger an e-fan based on A/C pressure with this operating system?
Short notes:
You cannot change your pressure sensor type. If your PCM ran a pressure sensor from the factory that is what you are stuck with. If it had high/low pressure switches your stuck with those. Even if your PCM/OS was used with either setup you cannot change between them with HPTuners.
You can change your a/c request type up to a point. You can change between serial and analog or between analog cycling and serial cycling. You cannot change from serial to analog cycling or serial cycling to analog. HPTuners will let you make the change but the PCM will not function with it. I have no idea what the "passive" option does.
I`m working with a 2003 blue/green pcm # 12576106 operating system # 12579405. This PCM and OS were used in both trucks/suv`s and vans with serial (trucks/suv`s) and analog cycling (vans) a/c request types. Since this PCM and OS was used both with the pressure switch and sensors and as a serial or analog cycling request I thought that I would be able to simply change my request type from serial to analog cycling, ground C2 pin 55, give +12v to C2 pin 17, and get the pcm to bump my idle and turn the fans on.
Turns out the PCM would acknowledge the A/C request but would not bump the idle, energize the a/c relay or fans as it was looking for the pressure sensor signal not the ground from the low pressure switch. I was kinda pissed but realized this OS was also used in the vans....so I changed my platform type to GMT610. This did not work as it was still looking for the pressure sensor. I really don`t understand why as this OS was used in both trucks and vans. So I changed back to the GMT800 platform and added 2 100K resistors in parallel (I didn`t have any resistors between 47k and 100k on hand so the 2 paralleled 100`s make approx 50k) in place of the pressure sensor. Now I had the PCM accepting an 12v a/c request and the PCM was seeing ~228psi of pressure but it still would not bump the idle, trigger the clutch relay or the fans. I tried using the tech 2 to manually enable the clutch relay but it told me the A/C pressure was out of normal range. I tried using different resistors and varied the a/c pressure between 91 and 372 psi but nothing worked and the tech 2 always said the a/c pressure was out of range if I tried to enable the relay manually.
Finally I changed my a/c request type to analog. That fixed most of the issues. Now with +12v to C2 pin 17 and the 2 100k parallel resistors between pin C1 45 and C2 pin 14 the PCM would trigger the a/c clutch relay and the idle would bump up. I still am not able to trigger the fans no matter where I set the fan 1/2 enable A/C pressure, but I know this truck had a mechanical fan from the factory so maybe it is impossible to trigger an e-fan based on A/C pressure with this operating system?
Short notes:
You cannot change your pressure sensor type. If your PCM ran a pressure sensor from the factory that is what you are stuck with. If it had high/low pressure switches your stuck with those. Even if your PCM/OS was used with either setup you cannot change between them with HPTuners.
You can change your a/c request type up to a point. You can change between serial and analog or between analog cycling and serial cycling. You cannot change from serial to analog cycling or serial cycling to analog. HPTuners will let you make the change but the PCM will not function with it. I have no idea what the "passive" option does.
09-08-2015, 01:28 PM
#30
Teching In
Join Date: Jan 2014
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
That sounds almost identical to the issues I am having except I am already using the 02 fbody os, and I've tried multiple sensors, just not one off an 02 camaro, which I am almost sure will not fit on my high pressure threads.
That's why the guys on the thirdgen.org suggest this one in particular. I also tried one from a 93-97 lt1 fbody with same results. Sees 4.55volts. I put the car on a set of autozone ac gauges and saw about 35 on low and 100 on high side, which I know should be higher on high side. I am totally at my wits ends, and thinking I am going to buy a new set of gauges for my own use, and test to see what they show. If need be I'll charge it more, but it seems to me if its at that 4.5v it should be showing a much higher gauge pressure from calculations I saw someone else post in a spreadsheet.
I don't want to damage the new compressor and just jumper it to run and would prefer not to half *** it, since spending so much money on it. I asked HPT support about it and have had no advice from them. I am a little off put that they don't give more control or show more details.
That's why the guys on the thirdgen.org suggest this one in particular. I also tried one from a 93-97 lt1 fbody with same results. Sees 4.55volts. I put the car on a set of autozone ac gauges and saw about 35 on low and 100 on high side, which I know should be higher on high side. I am totally at my wits ends, and thinking I am going to buy a new set of gauges for my own use, and test to see what they show. If need be I'll charge it more, but it seems to me if its at that 4.5v it should be showing a much higher gauge pressure from calculations I saw someone else post in a spreadsheet.
I don't want to damage the new compressor and just jumper it to run and would prefer not to half *** it, since spending so much money on it. I asked HPT support about it and have had no advice from them. I am a little off put that they don't give more control or show more details.
09-17-2015, 07:00 AM
#31
Well after spending hours playing with HPTuners and a tech 2 I have found that the A/C request switch feature only partially works. You don`t have as much capability to change the A/C request type as the options in HPTuners would lead you to believe
You cannot change your pressure sensor type. If your PCM ran a pressure sensor from the factory that is what you are stuck with. If it had high/low pressure switches your stuck with those. Even if your PCM/OS was used with either setup you cannot change between them with HPTuners.
You can change your a/c request type up to a point. You can change between serial and analog or between analog cycling and serial cycling. You cannot change from serial to analog cycling or serial cycling to analog. HPTuners will let you make the change but the PCM will not function with it. I have no idea what the "passive" option does.
You cannot change your pressure sensor type. If your PCM ran a pressure sensor from the factory that is what you are stuck with. If it had high/low pressure switches your stuck with those. Even if your PCM/OS was used with either setup you cannot change between them with HPTuners.
You can change your a/c request type up to a point. You can change between serial and analog or between analog cycling and serial cycling. You cannot change from serial to analog cycling or serial cycling to analog. HPTuners will let you make the change but the PCM will not function with it. I have no idea what the "passive" option does.
09-17-2015, 01:21 PM
#32
Yep, its just the fans that I have not been able to get to work. I thought I would be able to use the express van wiring and just change to cycling analog but that does not work. For whatever reason you have to keep the silverado wiring and change the request type to analog. It sees the a/c request, bumps the idle up and does everything but turn the fans on.
09-17-2015, 09:33 PM
#33
Yep, its just the fans that I have not been able to get to work. I thought I would be able to use the express van wiring and just change to cycling analog but that does not work. For whatever reason you have to keep the silverado wiring and change the request type to analog. It sees the a/c request, bumps the idle up and does everything but turn the fans on.
When you say you got it to work by wiring in the resistors to trick the PCM into seeing a set pressure, wouldn't that just make the compressor run all the time and probably freeze it up? I suppose I could try and find a 2005ish Express van tune with DBW and a 4l80, but as of now I have only seen DBC throttle bodies in the older GenIII vans.
09-18-2015, 09:56 AM
#34
Right I`m fairly confident that you can`t wire your 04 silverado like a van and get it to work. What OS are you currently running and was it from A vehicle with a pressure sensor or high/low switches?
You can also use the resistor trick. Wire your A/C switch in the car through your low pressure switch on the vehicle and then to pin 17. (You can also tie the high pressure cutout into that line if your using one.) Then wire a resistor in place of the pressure switch. The PCM will not command the A/C relay on unless the pressure switch is within operating range AND pin 17 has 12v supplied to it.
Sadly swapping to an express van tune does not fix the issue as I have been told the express van tune will not command the electric fans on due to an a/c request as no express van ever had e-fans so GM didn`t put that command line in the programming. If you want to try an express van OS go after OS # 12592618 or 12587811. Both are supposed to be very versatile and can run DBW, cable TB, 80e/60e, flex fuel sensor, etc. I have not verified that personally as my turbo car is still not together but thats what I have read about them and the options seem to be there in HPTuners. The 2618 OS is more widely used it seems.
You can also use the resistor trick. Wire your A/C switch in the car through your low pressure switch on the vehicle and then to pin 17. (You can also tie the high pressure cutout into that line if your using one.) Then wire a resistor in place of the pressure switch. The PCM will not command the A/C relay on unless the pressure switch is within operating range AND pin 17 has 12v supplied to it.
Sadly swapping to an express van tune does not fix the issue as I have been told the express van tune will not command the electric fans on due to an a/c request as no express van ever had e-fans so GM didn`t put that command line in the programming. If you want to try an express van OS go after OS # 12592618 or 12587811. Both are supposed to be very versatile and can run DBW, cable TB, 80e/60e, flex fuel sensor, etc. I have not verified that personally as my turbo car is still not together but thats what I have read about them and the options seem to be there in HPTuners. The 2618 OS is more widely used it seems.
09-19-2015, 05:46 PM
#35
I'm doing swap into a 79 f150 would it be best to use 79 wiring just connect old compressor clutch to new compressor or should I wire old clutch wire as a/c request?
What switch is in back of a/c compressor? 02 Tahoe engine compress n Harness. 79 f150 doesn't seem to have any pressure switches. Will look at diagram for f150
What switch is in back of a/c compressor? 02 Tahoe engine compress n Harness. 79 f150 doesn't seem to have any pressure switches. Will look at diagram for f150
09-21-2015, 07:56 PM
#36
Staging Lane
I'm using the F-body OS on a 411 PCM wired correctly with a pressure sensor and (incorrectly) with a ground from the low pressure switch to C2 55. I'm using a Sanden 508 fixed compressor and initially had the same problems, the PCM wouldn't energize the relay. After experimenting with different OS's, switches and wiring I ended up stumbling across my current setup which engages the compressor, fans and ups the idle.
09-29-2015, 07:07 AM
#38
Staging Lane
09-29-2015, 08:01 AM
#39
I'm using the F-body OS on a 411 PCM wired correctly with a pressure sensor and (incorrectly) with a ground from the low pressure switch to C2 55. I'm using a Sanden 508 fixed compressor and initially had the same problems, the PCM wouldn't energize the relay. After experimenting with different OS's, switches and wiring I ended up stumbling across my current setup which engages the compressor, fans and ups the idle.
10-12-2015, 11:36 AM
#40
I figured out why my fans would not engage.
My A/C Fans Disable speed was set to 0mph. I did not think this was a problem as the HPTuners description states "A/C Fans Disable speed: If the AC is on both fans will disable if speed is above this value and other thresholds are not met". Now my Fan 1 AC enable pressure was already set to 225 and disable to 220 (I`m not running a pressure switch so I faked it with a resistor that reads 228psi) I assumed that since my a/c pressure was above 225 the fans would enable as "other thresholds" would be met.
I changed the AC Fans disable speed to 40mph and the fans came right on.....always on... (due to my AC pressure constantly being 228 even with the A/C turned off). I thought I was onto something and tried raising the Fan 1 AC enable pressure to 250 thinking that would allow the fans to turn off when the A/C request was off, but turn the fans on when the request was on and speed was below 40mph. No luck there, now the fans would not enable regardless of speed or A/C request status. Looks like I will either have to put a pressure sensor inline to monitor the actual pressure, or use a relay to enable to a/c pressure sensor resistor bypass only when the compressor is running.
Cliffnotes, In order for the fans to activate BOTH the Fan 1 AC enable pressure AND the A/C Fans Disable speed conditions must be met. Not either/or like the HPT notes would lead you to believe.
My A/C Fans Disable speed was set to 0mph. I did not think this was a problem as the HPTuners description states "A/C Fans Disable speed: If the AC is on both fans will disable if speed is above this value and other thresholds are not met". Now my Fan 1 AC enable pressure was already set to 225 and disable to 220 (I`m not running a pressure switch so I faked it with a resistor that reads 228psi) I assumed that since my a/c pressure was above 225 the fans would enable as "other thresholds" would be met.
I changed the AC Fans disable speed to 40mph and the fans came right on.....always on... (due to my AC pressure constantly being 228 even with the A/C turned off). I thought I was onto something and tried raising the Fan 1 AC enable pressure to 250 thinking that would allow the fans to turn off when the A/C request was off, but turn the fans on when the request was on and speed was below 40mph. No luck there, now the fans would not enable regardless of speed or A/C request status. Looks like I will either have to put a pressure sensor inline to monitor the actual pressure, or use a relay to enable to a/c pressure sensor resistor bypass only when the compressor is running.
Cliffnotes, In order for the fans to activate BOTH the Fan 1 AC enable pressure AND the A/C Fans Disable speed conditions must be met. Not either/or like the HPT notes would lead you to believe.