A/C issue, any ideas?

[357i]

Trying to get my a/c set up to work on my swap and running into an issue. I have the pressure switch bypassed(jumped the high pressure side) and am able to engage the compressor using the vcm scanner. But I can not engage the compressor by putting +12v to the green/white a/c request wire, in the red ECU connector, pin 17. I have not found any thing in hptuners that would block the a/c other than the disable rpm. Any ideas?

[IDRIVEAG8GT]

Check your fans Zone 1 and Zone 2 for proper operation.

[jimmyblue]

Are you sure that you have a pressure -switch- ? My
car has a sensor and neither short not open are happy
places.

Is A/C request active high, or active low?

[mecanicman]

Thats because the pcm grounds that wire, not power it up.

[mecanicman]

A/C Mode
The purpose of the air conditioning (A/C) system is to provide cool air and remove humidity from the interior of the vehicle. The vehicle operator can activate the A/C system by activating the following modes:

MAX A/C
A/C
BI-LEVEL
MIX-BLEND
FRONT DEFROST
The A/C system can operate regardless of the temperature setting, as long as the ambient air temperature is above 3°C (38°F). If the A/C compressor clutch is turned off due to cold ambient air temperatures, the compressor will not come back on until ambient air temperatures reach 5°C (41°F).

Regardless of the selected A/C mode setting, a request is made to the powertrain control module (PCM) to turn on the A/C compressor clutch. The request is made through the A/C request signal circuit from the HVAC control assembly. Power and ground are provided to the HVAC control assembly by the ignition 3 voltage and ground circuits.

When the vehicle operator makes an A/C request, a 12 volt request signal is sent out over the A/C request signal circuit and grounded through the PCM . When this request signal is grounded, the PCM can activate the A/C compressor clutch.

The PCM turns on the A/C compressor clutch by providing a path to ground through the A/C compressor clutch relay control circuit for the A/C compressor clutch relay. Power is provided to the A/C compressor clutch relay from of the underhood fuse block on the ignition 1 voltage circuit. Once the relay closes its internal switch, power from the battery is provided to the A/C compressor clutch through the A/C compressor clutch supply voltage circuit. Whenever the compressor is turned off, the A/C compressor clutch diode prevents a voltage spike from entering the vehicles electrical system. The ground circuit provides a path to ground for the compressor. The A/C compressor clutch relay control circuit is grounded internally within the PCM. On vehicles with the V8 option, an A/C compressor clutch status signal is sent to the PCM on the A/C compressor clutch supply voltage circuit.

The PCM will engage the A/C compressor clutch any time the engine speed is below 5000 RPM and the A/C is requested unless any of the wing conditions exist:

Throttle angle is at 100 percent (WOT).
Vehicle launch, hard acceleration from a stop.
Idle quality
The A/C refrigerant pressure sensor is above 2854 kPa (414 psi) or is less than 241 kPa (35 psi).
Engine speed is more than 5500 RPM.
Engine coolant temperature (ECT) is more than 121°C (250°F) for the L36 and 125°C (257°F) for the LS1.
Transmission shift
Engine torque load
Top of travel clutch switch position, if equipped
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 2854 kPa (414 psi) or fall below 241 kPa (35 psi), the PCM will turn off the A/C compressor clutch. When high side pressures drop back down between 269-1724 kPa (39-250 psi), 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.

Recirculation Mode
Recirculation is only available in MAX A/C. When MAX A/C mode is selected, vacuum is applied to the recirculation actuator. The force of the vacuum overcomes the spring pressure inside the actuator, which is linked to the recirculation door, into recirculation mode. This brings air from inside the vehicle instead of fresh air from the outside.

Air Temperature Control
The temperature control knob regulates the HVAC system air temperature in any mode. A temperature control cable mechanically links the knob to the temperature door.



Does not look like you can bypass the pressure switch on this one, must be used.

[flame]

Need more info the truck pcm uses pressure switches and the cars use a pressure transducer. What motor, wiring, pcm are you using?

[pdsq98gt]

Did you ever get this to work? We just swapped an ls1 into an s10 and are running into a similar problem. Supposedly current performance set the harness up like a 99-02 truck and we have tuned it to f-body specs. Is it possible to do an a/c segment swap from a 99-02 truck and get this to work?