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
- Screwdriver set
- Protective gloves and eye wear
Begin with the vehicle on level ground, engine off (cold) in park with the emergency
Step 1 - A heater cannot operate unless the engine
is full of coolant/antifreeze.
If coolant level
is low check the system for leaks
Step 2 - 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 -
Blend Door Actuator
Refilling Cooling System
Step 3 - Inspect heater system vacuum lines especially
to the heater control valve. These
Blend Door Actuator
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.
Step 4 - The
Broken Vacuum Line
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.
Step 5 - Use a vacuum gauge to test various control
tubes which are used to move
Heater Control Valve
, 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.
Step 6 - The
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.
Step 7 - If
is being produced from the vents while the heater is in operation inspect the
Step 8 - A
cabin air filter
helps clean the air before it enters the passenger compartment,
when this filter becomes plugged it stops the airflow and needs to be
can be low
Replacing Air Cabin Filter
, especially in winter conditions. A
can be actuated by either a vacuum line or control cable.
To warm the passenger cabin, the heater system makes use of heat generated from
the engine by blowing across the
and onward through the system duct work.
When a heater core develops a leak, there are usually two indications, steam
could be produced from the vent system and is accompanied by a
, or the passenger floor can become wet from leaking coolant, these
are signs the core
If further assistance is needed, our certified technicians are ready
to answer your car repair questions for free
Article first published 2016-02-05