Operation CHARM: Car repair manuals for everyone.
Home >> Subaru >> 1990 >> Legacy Sedan 4WD F4-2.2L SOHC >> Repair and Diagnosis >> Relays and Modules >> Relays and Modules - HVAC >> Control Module HVAC >> Description and Operation
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

Control Module HVAC: Description and Operation

Fan Control Amplifier




The fan control amplifier is located on the cooling unit. It amplifies a 12-step base current flowing from the auto amplifier to change blower speed.


Hi Relay




The Hi relay is located on the heater unit. It receives a signal from the auto amplifier to operate the blower motor at high speed.

pro multis · About Operation CHARM