I have a 58 chevy pickup with a 2004 5.3L and 4l60e trans. I am getting ready to put an air conditioning unit in from Hot Rod air. Is there a way to get a high idle when the air in on. Maybe a signal to a pinout or ? Thanks Mark

 

You can adjust for it in the tune.

 

The wiring harness only controls the engine at this point. I cant use the original variable compressor on the aftermarket ac. All the aftermarket companies use the old style compressor that turns off and on. Are you suggesting turning up the idle at all times? This is my first computer contolled engine so maybe I'm not understanding you. Thanks Mark

 

oh, you might look into controling the compressor with the PCM, the PCM can adjust the idle to compensate for the compressor load.

 

I had a small wire harness problem when getting this thing running and learned a little about what pin assignment on the pcm go where but I dont know about what would control a high idle. Any info? Thanks Mark

 

PCM Controlled Air Conditioning

In order to improve engine operation, and protect the A/C compressor and A/C clutch during Wide Open Throttle (WOT) performance, the A/C compressor operation is controlled by the PCM.

This A/C system consists of the following components:


The heater and A/C control module
The A/C high pressure cut-out switch
The A/C compressor cycling switch
The A/C compressor clutch relay
The A/C compressor clutch
The PCM
When the heater and A/C control module is placed in an A/C mode, a request signal is sent to the PCM. The PCM will then energize the A/C clutch relay, unless abnormally high or low A/C pressure is detected. The A/C clutch relay is controlled by the PCM so that the PCM can increase idle speed before turning ON the clutch, or disable the clutch during WOT or high coolant temperature.

The PCM energizes the A/C clutch whenever the engine is running less than 5,000 RPM and the A/C has been requested, unless any of the following conditions are met:


wide open throttle (WOT)
The A/C compressor cycling switch pressure is less than 18 psi or more than 45 psi .
The A/C high pressure cutout switch pressure is more than 420 psi .
The engine speed is more than 5,500 RPM .
ECT is more than 121°C (250°F) .
Any of the conditions described above inhibits the A/C compressor relay operation.


HVAC COMPRESSOR CONTROLS CIRCUIT DESCRIPTION

The HVAC air delivery electrical system consists of a control module, blower switch, mode and temperature potentiometers & (motors), recirculating outside air control push button, temperature, mode and recirculating motors that operate their respective actuators and doors.

The mode, recirculating and temperature door motors are powered by ignition 3 voltage when the ignition switch is in the RUN position. The ground path is provided by the body wiring harness junction block to ground located in the left hand upper plenum area. The HVAC control module is powered by ignition 3 voltage from the HVAC fuse located in the fuse block when the ignition switch is in the RUN position. Grounding for the module is through the same circuit utilized for the door motors.

The recirculating door motor is controlled by a signal from the HVAC control module via recirculation actuator control when the push button is activated on the control head. Also, the recirculation door motor can be controlled by the PCM which monitors the automatic recirculation switch activity (located at the bottom right hand side of the Air Conditioning (A/C) condenser) and will signal the door motor to the recirculating mode when the switch closes due to high refrigerant pressure. This will allow cooler air from inside the vehicle to flow over the A/C evaporator thus cooling the refrigerant temperature.

The mode and temperature door motors are positioned in proportion to the variable voltage signal received from the HVAC control module. Adjusting the temperature dial (potentiometer) in the control head provided a variable (0-5 volts ) voltage to the door motor via temp actuator control. There is a constant 5 volt reference sent to both motors via 5 volt reference from the control module. The module uses this reference voltage to accurately determine the door motor position through a feed back temp actuator signal which also varies from 0-5 Volts .

The air delivery mode functions consist of vent, bi-level, heater, defog and defrost (non rear HVAC vehicles) and upper or lower (Rear HVAC vehicles). The mode door motor operates in the same manner as the temperature door except for the signal and feed back circuits which are mode actuator control and mode actuator signal respectively. The HVAC control module receives a mode signal from the control head and will adjust the voltage control signal to the motor in accordance with the mode selected.


A/C Request Signal

The A/C request circuit signals the PCM when an A/C mode is selected at the A/C control head. The PCM uses this information in order to enable the A/C compressor clutch and to adjust the idle speed before turning ON the A/C clutch. If the A/C high pressure switch is open, the A/C request will not be detected by the PCM. The PCM also disables the A/C compressor clutch if the A/C request signal is not available to the PCM due to a high refrigerant pressure condition.






Check out the attached diagrams for a visual. Hope you've gained further knowledge of what you need. Don't forget to post pics of the truck and powertrain.