Step by step guide on how to
fix your heater, this information pertains to most cars, trucks and SUV's.
Difficulty Scale: 4 of 10
Tools and Supplies Needed
Protective gloves and eye wear
Begin with the vehicle on level ground, engine off (cold) in park with the emergency
Heater Controls - A heater cannot operate unless the engine
is full of coolant/antifreeze.
Step 1 If coolant level
is low check the system for leaks
Refilling Cooling System - The
control the rate in which the engine heats up. If this unit is stuck
open the engine will stay at a low temperature which created little to no heat for
the heater. Visit -
Engine Thermostat - The heater control air blend door is controlled
by a electronic/vacuum/cable which can malfunction causing a problem. Check the
door operation by moving the heat control from hot the cold while listening for
moment inside the heater plenum. Please Visit -
Step 3 Blend Door Actuator
Blend Door Actuator - this problem happens more than I thought
at first, but after reviewing many posts with the same problem the fix was relatively
simple. With the engine running at full temp jack the front of the car up and let
it run for 2 minutes then go to the rear of the car and do the same thing, this
will burp or purge the air bubbles locked in the heater core and allow the heater
to work again.
- Inspect heater system vacuum lines especially
to the heater control valve. These
can cause the system to not function. If a hissing noise is present under
the dash when the engine is running a vacuum leak exists and must be repaired to
restore the heater functionality.
Broken Vacuum Line - The
prevents the flow of
the heater core during the
function, occasionally this valve will stick not allowing hot coolant to flow, inspect
the valve for movement while in operation.
Heater Control Valve - Use a vacuum gauge to test various control
tubes which are used to move
Step 7 blend
, also use a hand held vacuum pump to test servo diaphragms by
connecting to the vacuum port directly. If no vacuum is present, open the hood and
inspect all small vacuum lines from the
to the firewall and
under the dash, this test can be used for the heater control valve as well.
Vacuum Gauge - The
Step 8 heater core
is responsible for converting hot coolant into heated air, if this core becomes
plugged it will not operate correctly. To check for a plugged heater core, start
the vehicle and allow the engine to warm up to normal operating temperature while
turning the heater to its hottest setting. Grasp both
they both should be hot, if only one is hot, the core could be plugged or the heater
control valve is malfunctioning.
Heater Core - If
Step 9 no air
is being produced from the vents while the heater is in operation inspect the
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