Cold-Start Arrest

Cold-Start Arrest







If, at engine start-up, engine coolant temperature is below 86 °F (30 °C), and the left Y-factor is 100%, the control module automatically initiates the cold-start arrest function. The purpose is to avoid cold drafts in the passenger compartment.


NOTE: Cold-start arrest is overridden if the "maximum defrost" program is selected or if the blower control thumbwheel is in the maximum speed detent position at engine start-up.


Cold-start arrest operation is as follows:
- The defroster flaps are fully opened; at other air distribution flaps are fully closed.
- The blower runs at very low speed (3 volts).
- The A/C compressor is turned "Off".
- The auxiliary coolant pump is turned "Off".

The control module monitors the coolant temperature as the engine warms up:
- When coolant temperature reaches 68 °F (20 °C), the module increases blower voltage with temperature.
- At 86 °F (30 °C), the A/C compressor is enabled, the auxiliary coolant pump is turned "On", and air distribution is determined by control panel button positions.
- Above 122 °F (50 °C), blower voltage is determined by blower speed thumbwheel position.

Beginning with software version "03" (from 12/88 production), the A/C compressor operates during cold-start arrest if the A/C compressor push button is depressed, to help prevent window fogging following engine start-up.


NOTE: Also beginning with software version "03", if the IHKA system is "off", at engine start-up and remains "off" as the engine warms up, the blower motor turns off automatically when the cold-start arrest function ends.