Skip to content

2.3 HVAC System

Type: Factory HVAC System

Model: 2005 TJ/LJ HVAC Assembly

Manufacturer: Chrysler/Jeep (OEM)

Mounting: Factory under-dash location

Power Source: PMU OUT5 (blower motor), OUT17 (A/C clutch)

Control: Factory TJ HVAC control panel

Overview

Factory 2005 TJ HVAC system retained. Uses vacuum-operated mode doors, cable-operated temperature blend door, and factory dash control panel. Requires only 2 PMU outputs.

PMU Integration

Circuit PMU Load Control Notes
Blower Motor OUT5 (25A) ~20A max Auto (ignition ON) Factory resistor pack controls speed
A/C Clutch OUT17 (7A) 3-5A In 9 trigger Factory A/C button → PMU In 9

See PMU Outputs for complete configuration.

Control Methods

Function Control Type PMU Involvement
Blower Speed Electrical (resistor pack) OUT5 provides power
A/C On/Off Electrical (PMU switched) In 9 triggers OUT17
Temperature Mechanical (cable) None
Mode (defrost/vent/floor) Vacuum None
Recirculation Vacuum None

Vacuum System

Source: R2.8 intake manifold → check valve → reservoir → firewall → factory HVAC controls

Components: 10-15 ft vacuum line (1/4" ID), check valve, vacuum reservoir, tee fittings

R2.8 ECM A/C Integration (Optional)

The R2.8 ECM may have an A/C request input that enables idle speed bump when the compressor engages. This compensates for the additional load and prevents rough idle.

Signal Direction Purpose Status
A/C Request PMU → R2.8 ECM Tell ECM when A/C clutch is engaged TBD - verify ECM pin

If ECM has A/C input: Wire PMU OUT17 (or parallel signal) to ECM A/C request pin.

If ECM lacks A/C input: No action needed - idle may dip slightly when A/C engages but not critical.

Outstanding Items

  • Verify if R2.8 CM2220 ECM has A/C request input pin (check Cummins wiring diagram via QuickServe Online)
  • If available, wire A/C signal from PMU to ECM for idle bump compensation

See installation checklist for build tasks.