1989 Mercury Marquis NO HEAT IN PASSENGER CABIN

CWISENER

MEMBER
1989 MERCURY MARQUIS
V8
2WD
AUTOMATIC
11,000 MILES

STATUS: CLIMATE CONTROL SYSTEM PROVIDING 0% HEATED AIR TO PASS. CABIN. TEMP. ** CLIMATE CONTROL SYSTEM STATUS***> TEMP CONTROL VALVE - OK, (2)HEATER CORE WATER LINES ARE WARM AT BOTH INLET/OUTLET CONNECTIONS, (3) SERVO MOTOR OPERATING ACCESS DOORS AS DESIGNED. (4) TEMP CONTROL CABLE IS CONNECTED AND OPERATIONAL (5) VENT AIR DIST. POINTS ARE ALL OPERATING CORRECTLY My Question is: WHAT COULD PREVENT HEATED AIR FROM HEATER CORE COMPARTMENT REACHING THE AUTO CLIMATE CONTROL SYSTEM FOR DISTRIBUTION INTO PASSENGER CABIN? I HAVE EXUASTED ANY ADDTL. OPTIONS FOR REPAIR DOCS, MANUALS AND SELF HELP RESOURCES. **************PLEASE REPLY WITH ANY DIAGNOSES, SOULTIONS, DIAGRAMS, TROUBLESHOOTING PROCEDURES, AND POSSIBLE FAUTLY PART DESCP./ PART# ETC. (DESPERATE IN DALLAS) {chris wisener} cwisener@msn. Com (972)836-2768

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

Heater Core "” Plugged

WARNING: The heater core inlet hose will become too hot to handle if the system is working correctly.

Check to see that the engine coolant is at the correct level.
Start the engine and turn on the heater.
When the engine coolant reaches operating temperature, feel the heater core inlet and outlet hose to see if they are hot.
If the inlet hose is not hot:

the thermostat is not working correctly.
If the outlet hose is not hot:

the heater core may have an air pocket.
The heater core may be restricted or plugged.
If both are hot, the temperature blend door in the heater plenum may be broken or stuck.