A/C request fix works for me hope it helps others.
05-26-2014, 05:14 PM
#1
A/C request fix works for me hope it helps others. I just completed a conversion using my stock vehicle a/c wiring including (pressure sensor), just wanted to add the ls1 ECU for cut out on starting, idle raise ect ect, and what a headache this was.
SO originaly my ECM had its A/C driven by the body control module which i had deleted, so i wired the ECM directly, still with no success, I had a real time scan tool connected and everything should have worked As request was saying it was registering, I could force the a/c to work, but could not get the ecm to run it as needed. After hours of searching and reading issues others had, especially after segment swaps, I've joined a few ideas together and have it working sweet, I hope this helps others, I don't think I have re invented the wheel maybe just made it easier for others. PIN 55 (oh how hard you were to figure out)
AC Request.
Please be aware wiring this system as i have drawn/modified you need to make sure you have a pressure sensor installed in your system "pre the ls1 component" otherwise there is risk of over pressurizing the a/c system.
SO originaly my ECM had its A/C driven by the body control module which i had deleted, so i wired the ECM directly, still with no success, I had a real time scan tool connected and everything should have worked As request was saying it was registering, I could force the a/c to work, but could not get the ecm to run it as needed. After hours of searching and reading issues others had, especially after segment swaps, I've joined a few ideas together and have it working sweet, I hope this helps others, I don't think I have re invented the wheel maybe just made it easier for others. PIN 55 (oh how hard you were to figure out)
AC Request.
Please be aware wiring this system as i have drawn/modified you need to make sure you have a pressure sensor installed in your system "pre the ls1 component" otherwise there is risk of over pressurizing the a/c system.
The following 2 users liked this post by 80gus:
All_gas_NO_brakes (04-22-2020), newby96 (05-17-2022)
05-26-2014, 06:28 PM
#3
This is working on a gto based harness with a 4l80e van segment swap
05-27-2014, 09:24 AM
#6
TECH Enthusiast
Not sure why you want to fake the pressure sensor other than to get the ECM to control the idle. All you need to do is this:
1. Decide on the compressor -fixed or variable.
2. Wire the system for the above with either a pressure switch for a fixed and sensor for a variable (not both).
3. Program the PCM for the compressor type.
The wiring diagram for a 02 Camaro or a 02 Express van can be followed. The Camaro uses a variable compressor with the sensor and the Express vans and trucks use a fixed compressor with a pressure switch. The difference is because the fixed compressors cycle and the variables do not. If you do not cycle the fixed compressor you may get the evaporator freezing up. Since it appears that you are running a fixed compressor you can easily eliminate the purple wire by programming the PCM to be a fixed compressor and wiring it as such. The problem you encountered is because you did not switch the type of compressor. The 04 GTO and any Red/Green OS will work the same way regardless of how the original OS is wired including the A/C systems using serial data and of course the GTO's using the BCM's.
1. Decide on the compressor -fixed or variable.
2. Wire the system for the above with either a pressure switch for a fixed and sensor for a variable (not both).
3. Program the PCM for the compressor type.
The wiring diagram for a 02 Camaro or a 02 Express van can be followed. The Camaro uses a variable compressor with the sensor and the Express vans and trucks use a fixed compressor with a pressure switch. The difference is because the fixed compressors cycle and the variables do not. If you do not cycle the fixed compressor you may get the evaporator freezing up. Since it appears that you are running a fixed compressor you can easily eliminate the purple wire by programming the PCM to be a fixed compressor and wiring it as such. The problem you encountered is because you did not switch the type of compressor. The 04 GTO and any Red/Green OS will work the same way regardless of how the original OS is wired including the A/C systems using serial data and of course the GTO's using the BCM's.
Last edited by 69 Ghost; 05-27-2014 at 09:32 AM.
05-27-2014, 10:06 AM
#7
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THe only thing pin 55 would do is cut the A/C if the charge was low. (I would think) the cycling switch should be a no brainer if your running a fixed A/C.
So 80GUS, are you saying it didnt work till you put that resistor on pin 55 to simulate a low pressure cutout switch?
So 80GUS, are you saying it didnt work till you put that resistor on pin 55 to simulate a low pressure cutout switch?
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05-27-2014, 03:03 PM
#8
Not sure why you want to fake the pressure sensor other than to get the ECM to control the idle. All you need to do is this:
1. Decide on the compressor -fixed or variable.
2. Wire the system for the above with either a pressure switch for a fixed and sensor for a variable (not both).
3. Program the PCM for the compressor type.
The wiring diagram for a 02 Camaro or a 02 Express van can be followed. The Camaro uses a variable compressor with the sensor and the Express vans and trucks use a fixed compressor with a pressure switch. The difference is because the fixed compressors cycle and the variables do not. If you do not cycle the fixed compressor you may get the evaporator freezing up. Since it appears that you are running a fixed compressor you can easily eliminate the purple wire by programming the PCM to be a fixed compressor and wiring it as such. The problem you encountered is because you did not switch the type of compressor. The 04 GTO and any Red/Green OS will work the same way regardless of how the original OS is wired including the A/C systems using serial data and of course the GTO's using the BCM's.
1. Decide on the compressor -fixed or variable.
2. Wire the system for the above with either a pressure switch for a fixed and sensor for a variable (not both).
3. Program the PCM for the compressor type.
The wiring diagram for a 02 Camaro or a 02 Express van can be followed. The Camaro uses a variable compressor with the sensor and the Express vans and trucks use a fixed compressor with a pressure switch. The difference is because the fixed compressors cycle and the variables do not. If you do not cycle the fixed compressor you may get the evaporator freezing up. Since it appears that you are running a fixed compressor you can easily eliminate the purple wire by programming the PCM to be a fixed compressor and wiring it as such. The problem you encountered is because you did not switch the type of compressor. The 04 GTO and any Red/Green OS will work the same way regardless of how the original OS is wired including the A/C systems using serial data and of course the GTO's using the BCM's.
I have 2 ECM's here that had both styles of compressor settings both were tried and neither would work. The resistor is needed to fake a pressure, thius wiring setup cycles via the original cars Pressure sensor and ECM, this is just a way to add the LS1 ECM into the system
06-03-2014, 08:57 AM
#10
TECH Enthusiast
Code:
I have 2 ECM's here that had both styles of compressor settings both were tried and neither would work. The resistor is needed to fake a pressure, thius wiring setup cycles via the original cars Pressure sensor and ECM, this is just a way to add the LS1 ECM into the system
06-03-2014, 12:56 PM
#11
Code:
I have 2 ECM's here that had both styles of compressor settings both were tried and neither would work. The resistor is needed to fake a pressure, thius wiring setup cycles via the original cars Pressure sensor and ECM, this is just a way to add the LS1 ECM into the system
06-03-2014, 04:06 PM
#12
TECH Enthusiast
So are you using a green/blue connector ecm? And you have it working with the 12v request and the pressure sensor like the 98-02 f-body is wired using a red/blue connector ecm?
06-04-2014, 08:26 AM
#14
If you run the Express tune, they are wired like the older99-02 trucks with the 12v request. The problem I had is I couldn't get the DBW from a 03-up truck to work. I hear that now HPTuners has an option to change the serial a/c request to 12v, I'm going to try it next time I do one.
06-04-2014, 09:23 AM
#15
TECH Enthusiast
If you run the Express tune, they are wired like the older99-02 trucks with the 12v request. The problem I had is I couldn't get the DBW from a 03-up truck to work. I hear that now HPTuners has an option to change the serial a/c request to 12v, I'm going to try it next time I do one.
06-04-2014, 09:41 PM
#16
If you run the Express tune, they are wired like the older99-02 trucks with the 12v request. The problem I had is I couldn't get the DBW from a 03-up truck to work. I hear that now HPTuners has an option to change the serial a/c request to 12v, I'm going to try it next time I do one.
06-04-2014, 09:43 PM
#17
I'm not using HPTuners I am using Tunercat. As far as I know there is no switch to change from the serial request to 12volt. The difference again is in the wiring, etc. The OS's have the wiring built in and are turned on by A/C compressor type. Funny you should mention that you could not get your DBW to work I just tested a 05 CTSV OS and could not get the IAC to work with a cable TB even though ETC was turned off in the matrix. The 05 express van uses the same OS and is DBC. I was going to test that OS but have not gotten around to changing the tables and putting it in the car.
http://lt1swap.com/cable_conversion.htm
06-05-2014, 09:09 AM
#19
TECH Enthusiast
The OS is the same, but the hardware in the ecm is different. Here is a link that explains it...
Here is the reason why I prefer the newer OS's and PCM's over the 411 which is by far the most popular...
http://www.superchevy.com/how-to/0704gm-factory-pcms/
Last edited by 69 Ghost; 06-05-2014 at 09:15 AM.
06-05-2014, 09:26 AM
#20
Not quite. The OS's are different the 04 Vette, 04 GTO, are different. The 05 CTSV and Express van's can have the same OS. The pressure sensor or switch along with the fan setup are controlled by the OS. All OS's have settings to change them. The real difference between the PCM's is if they have the IAC driver or not. Be careful if you decide to upgrade. The 243, 463, and 802 have the IAC drivers but the 242, 462, and 801's do not. If you are running a DBW setup then it does not matter. Other than that they are basically the same other than speed and memory. Note you can go to a newer PCM from the 99-02 as a plug and play but you have to change the O2 sensor wiring if you go the other way.....
Here is the reason why I prefer the newer OS's and PCM's over the 411 which is by far the most popular...
http://www.superchevy.com/how-to/0704gm-factory-pcms/
Here is the reason why I prefer the newer OS's and PCM's over the 411 which is by far the most popular...
http://www.superchevy.com/how-to/0704gm-factory-pcms/