Mode Control

Chevrolet:

Pontiac:

The mode control has eight settings: "OFF," "MAX," "A/C," "BI-LEVEL A/C," "VENT," "HEATER," "DEFROST BLEND," and "DEFROST." Some settings are symbols on the heater and air conditioning control (1). These symbols are identified in images 1 and 2. Each setting is described below.

"OFF" MODE

At this setting, electrical power is not supplied to the blower motor and A/C is not requested to the powertrain control module (PCM). A small amount of air which is forced into the heater and air conditioning module by forward movement of the vehicle will still be discharged through the heater and defrost outlets. This is the only mode in which the blower motor does not operate.

"MAX" A/C MODE

The "MAX" A/C setting is one of five settings which requests A/C operation to the PCM. At this setting the blower motor will operate in one of the four blower motor speed control settings and air will he discharged from the instrument panel air outlets only.

To provide maximum air conditioning, most of the air entering the heater and air conditioning module is taken from the vehicle interior (re-circulated) where it is most likely cooler than the outside air. This is the only mode in which air is re-circulated, all other modes use outside air only. This setting would be most useful during conditions of high temperature and humidity, or when the outside air may have an objectionable odor.

NORMAL "A/C" MODE

The normal "A/C" setting functions the same as "MAX" A/C setting, except only outside air enters the module. There may be a slight reduction of blower noise compared to "MAX" A/C mode because the re-circulation valve (door) is closed.

"BI-LEVEL A/C" MODE

The "BI-LEVEL A/C" setting requests A/C to the PCM and allows the blower motor to operate in one of four settings. Only outside air enters the module and air is distributed through the instrument panel outlets and the floor outlets with a small amount to the defrost outlet.

"VENT" MODE

The "VENT" setting does not request A/C to the PCM but allows the blower motor to operate normally. This is one of two economy modes (other than "OFF") in which A/C is not requested. Air is discharged through the instrument panel outlets only.

"HEATER" MODE

The "HEATER" setting functions the same as the "VENT" setting, except most of the air is discharged through the floor outlets with a small amount discharged through the defroster outlets. The "HEATER" mode is the normal selection for cold weather operation unless windshield defrosting or side window defogging is required.

"DEFROST BLEND" MODE

The "DEFROST BLEND" setting allows operation of the blower motor and sends an A/C request signal to the PCM for compressor operation. During this setting, air is discharged through the defroster and floor air outlets. This setting allows greater passenger comfort than "DEFROST" but is not as effective in defrosting the windshield and side windows.

"DEFROST" MODE

The DEFROST" setting functions the same as "DEFROST BLEND" setting except most of the air is discharged through the defroster outlets with a small amount going through the heater and side window defoggers.