AC Request: How does it work
02-23-2017, 05:34 PM
#61
Dan, going over my own personal notes, I noticed something about Camaro AC pinouts.
What year F body is your computer flashed as?
for instance 99 PCM uses blue #27, 34, 35 for the pressure switch.
02 PCM uses blue #14, 57 and red #45!
i don't have notes on the other years off hand but could this possibly explain your issue?
What year F body is your computer flashed as?
for instance 99 PCM uses blue #27, 34, 35 for the pressure switch.
02 PCM uses blue #14, 57 and red #45!
i don't have notes on the other years off hand but could this possibly explain your issue?
02-23-2017, 06:35 PM
#62
OK so 1st the f body doesn't use a "pressure switch". It uses a "pressure sensor" which is used for the GM variable displacement compressor which has an internal regulater that cycles the compressor. The Variable Displacement Compressor will not kick on if the pressure is too low. So best bet is to hook up a set of manifold gages to make sure u have the correct refrigerant level.
As for your refrigerant pressure sensor connector, a=1, b=2, c=3. So match it up with the pic u posted it above. Your 5v refrence signal is spliced into the iat temp sensor's 5v reference wire. The ground (low reference) shows correct on the pic u posted. The other wire is just the Refrigerant pressure sensor signal. From looking at your pics it seems that u have the wire sorrect.
I just wired up my standalone harness like this so it's fresh on my mind. Hope this helps some.
As for your refrigerant pressure sensor connector, a=1, b=2, c=3. So match it up with the pic u posted it above. Your 5v refrence signal is spliced into the iat temp sensor's 5v reference wire. The ground (low reference) shows correct on the pic u posted. The other wire is just the Refrigerant pressure sensor signal. From looking at your pics it seems that u have the wire sorrect.
I just wired up my standalone harness like this so it's fresh on my mind. Hope this helps some.
07-09-2017, 02:04 PM
#64
It has been a long time since I posted on this. Since my last post I swapped the AC request from pin 18 to pin 17, since PSI thought I had a different PCM. That didn't change anything and when I went to my tuner he told me that he was not seeing the AC request signal so I had just been living with the problem.
Then this summer I noticed that the AC would not blow cold until I was moving or the engine had warmed up enough to kick on the fans. Now remember I only have a binary switch that came with the Vintage AC kit. I really should have installed a trinary switch when I did this install since I have electric fans. Because of this I decided to add a relay that would ground one of the fan relays when the compressor got 12 volts. This way my fan would always run when the AC compressor was clutched in. I just finished doing this and it looks like my problems are solved.
Then this summer I noticed that the AC would not blow cold until I was moving or the engine had warmed up enough to kick on the fans. Now remember I only have a binary switch that came with the Vintage AC kit. I really should have installed a trinary switch when I did this install since I have electric fans. Because of this I decided to add a relay that would ground one of the fan relays when the compressor got 12 volts. This way my fan would always run when the AC compressor was clutched in. I just finished doing this and it looks like my problems are solved.
09-27-2017, 06:05 PM
#65
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Dan,
any luck on this?
I finally had a couple of free minutes at work. I searched our diagnostic database for testing data for the sensor, but it appears none exists (at least in our database).
I'll copy/paste the information I found on the sensor. This is the ONLY information listed aside from the actual wiring schematics. You already know the gist of this, but I'll post it anyway.
"2002 Chevrolet Camaro 5.7L Eng SS
1Search™
Print Date: 2/21/2017
hvac refrigerant switch/sensor
A/C Pressure Sensor [ A/C COMPRESSOR CLUTCH ]
Some models are equipped with an A/C pressure sensor which is used to inform PCM of A/C system pressure levels. Low pressure signal will cause A/C compressor to disengage to prevent system damage. High pressure levels cause PCM to engage high speed cooling fans while A/C compressor clutch is engaged. Extremely high pressure levels will cause PCM to disengage A/C compressor clutch to prevent system damage.
A/C Pressure Sensor [ INPUT DEVICES ]
Some models are equipped with an air conditioner pressure sensor which is used to inform PCM of A/C system pressure. PCM uses this signal to determine A/C compressor load on the engine to control idle speed with IAC valve. Failure in A/C pressure sensor circuit or with A/C pressure sensor should set a related diagnostic trouble code and A/C compressor clutch will become inoperative. A fixed high pressure value will exist if the ground circuit to sensor is faulty.
A/C Pressure Switches
A/C high and low pressure switches may be used in the PCM-monitored A/C request signal circuit. Switches are normally closed, completing the circuit between ignition and PCM. PCM will engage or disengage A/C clutch relay based upon status of this circuit. When system refrigerant pressure increases beyond a certain point, high side switch will open, causing A/C request line voltage to drop. If system refrigerant level decreases, causing refrigerant pressure to drop below normal, low side pressure switch will open, once again causing A/C request line voltage to drop. Switches may be used as normal clutch cycling devices or as safety devices which prevent compressor damage in the event of excessively high or low refrigerant pressure.
A/C Refrigerant Pressure Sensor
The A/C system is protected by the A/C refrigerant pressure sensor. The sensors output to the PCM is variable and is dependent upon pressure inside the line. A higher pressure results in a higher voltage output. The A/C pressure is constantly monitored in order to allow the A/C compressor clutch to disengage as needed. If line pressures climb above 414 psi (2854 kPa) or fall below 35 psi (241 kPa), the PCM will turn off the A/C compressor clutch. When high side pressures drop back down between 39-250 psi (269-1724 kPa), the PCM will allow the A/C compressor to operate.
A 5 volt reference signal is sent out over the 5 volt reference circuit, from the PCM, to the A/C refrigerant pressure sensor. The PCM reads the A/C pressure by monitoring the voltage on the A/C refrigerant pressure sensor signal circuit. Ground for the A/C refrigerant pressure sensor is provided by the low reference circuit."
any luck on this?
I finally had a couple of free minutes at work. I searched our diagnostic database for testing data for the sensor, but it appears none exists (at least in our database).
I'll copy/paste the information I found on the sensor. This is the ONLY information listed aside from the actual wiring schematics. You already know the gist of this, but I'll post it anyway.
"2002 Chevrolet Camaro 5.7L Eng SS
1Search™
Print Date: 2/21/2017
hvac refrigerant switch/sensor
A/C Pressure Sensor [ A/C COMPRESSOR CLUTCH ]
Some models are equipped with an A/C pressure sensor which is used to inform PCM of A/C system pressure levels. Low pressure signal will cause A/C compressor to disengage to prevent system damage. High pressure levels cause PCM to engage high speed cooling fans while A/C compressor clutch is engaged. Extremely high pressure levels will cause PCM to disengage A/C compressor clutch to prevent system damage.
A/C Pressure Sensor [ INPUT DEVICES ]
Some models are equipped with an air conditioner pressure sensor which is used to inform PCM of A/C system pressure. PCM uses this signal to determine A/C compressor load on the engine to control idle speed with IAC valve. Failure in A/C pressure sensor circuit or with A/C pressure sensor should set a related diagnostic trouble code and A/C compressor clutch will become inoperative. A fixed high pressure value will exist if the ground circuit to sensor is faulty.
A/C Pressure Switches
A/C high and low pressure switches may be used in the PCM-monitored A/C request signal circuit. Switches are normally closed, completing the circuit between ignition and PCM. PCM will engage or disengage A/C clutch relay based upon status of this circuit. When system refrigerant pressure increases beyond a certain point, high side switch will open, causing A/C request line voltage to drop. If system refrigerant level decreases, causing refrigerant pressure to drop below normal, low side pressure switch will open, once again causing A/C request line voltage to drop. Switches may be used as normal clutch cycling devices or as safety devices which prevent compressor damage in the event of excessively high or low refrigerant pressure.
A/C Refrigerant Pressure Sensor
The A/C system is protected by the A/C refrigerant pressure sensor. The sensors output to the PCM is variable and is dependent upon pressure inside the line. A higher pressure results in a higher voltage output. The A/C pressure is constantly monitored in order to allow the A/C compressor clutch to disengage as needed. If line pressures climb above 414 psi (2854 kPa) or fall below 35 psi (241 kPa), the PCM will turn off the A/C compressor clutch. When high side pressures drop back down between 39-250 psi (269-1724 kPa), the PCM will allow the A/C compressor to operate.
A 5 volt reference signal is sent out over the 5 volt reference circuit, from the PCM, to the A/C refrigerant pressure sensor. The PCM reads the A/C pressure by monitoring the voltage on the A/C refrigerant pressure sensor signal circuit. Ground for the A/C refrigerant pressure sensor is provided by the low reference circuit."
Pegged for future refrence
12-13-2019, 03:09 PM
#66
I know this is an old post. But, I'm swapping in a 2005 5.3 from a truck and I got all the harness etc. I can't seem to find any info on the Green/Blue connectors as to where to pin an A/C request or A/C on. I have identified and kept the wires going to the pressure sensor. The only pins I see in the pinout from LT1 in regards to A/C pinouts is pin #43 A/C clutch relay and pressure sensor and pin A3 on the C2 Underhood connector Any help would be appreciated.
Thanks
Thanks
Last edited by Plumber452; 12-14-2019 at 05:03 AM.
12-14-2019, 02:18 PM
#67
I know this is an old post. But, I'm swapping in a 2005 5.3 from a truck and I got all the harness etc. I can't seem to find any info on the Green/Blue connectors as to where to pin an A/C request or A/C on. I have identified and kept the wires going to the pressure sensor. The only pins I see in the pinout from LT1 in regards to A/C pinouts is pin #43 A/C clutch relay and pressure sensor and pin A3 on the C2 Underhood connector Any help would be appreciated.
Thanks
Thanks
12-16-2019, 09:06 PM
#68
There is a way to wire so that you can use an original, old style 12v request wire from an 80's or prior GM, using a fixed compressor, pressor sensor from a variable compressor wired to the PCM to control the electric fans, which can be wired up to run on high and low rather than left and right, and a high pressure switch from a fixed compressor to control the compressor. If you have a drive by wire you'd need a very specific PCM serial number and, as mentioned, wired like an express van. The fans would need to be wired like an 06 or so Tahoe. All this is explained in some threads here and I think I listed all the parts in my Caprice build. That's how I wired my Caprice up with help from the forum members.