How to Replace a Heater Control Valve
For heat to enter your vehicle, hot engine coolant needs to enter the vehicle’s
. However, that flow of hot coolant needs to be regulated or you
would have heat entering the vehicle at all times. Some vehicles use a blend air
door to stop heat from entering the vehicle. Other vehicles have a heater
control valve.The heater control valve
is nothing more than a valve that is closed and opened
by a cable when you change your controls in the vehicle from cold to hot. At
that point, like a spigot in your house, coolant is allowed to flow through the
heater core. From the hot coolant
, the core gets hot and allows heat to enter
Like any other mechanical component, heater control valves go bad. Some will
actually develop enough corrosion on them that you can’t open and close it. As a
result, you get no heat in the vehicle
. Others can begin to leak coolant.
Regardless, they are easy to replace and not very expensive.Parts and Supplies needed to Replace a Heater Control Valve
1. Coolant2. New Heater Control Valve3. New Hose Clamps4. New Heater Hose (optional)5. Protective Clothing6. Eye protectionTools Needed to Complete this Job
1. Screwdriver2. Pliers3. Large Drain Pan to Collect Used CoolantInstructions
Step 1. Park the vehicle on a flat surface, place the parking brake on, and
place the vehicle in park (A/T) or in reverse (M/T)
Step 2. Allow the engine to fully cool so that the radiator is cool to the
touch.Step 3. Locate the radiator drain plug on the lower section of the radiator. It
will look like a wing nut. Place the large drain pan under it and drain
approximately half of the coolant from the radiator.
Step 4. Place the coolant in a safe place to be reused. NOTE: Animals are
attracted to coolant. It can be fatal if they drink it, so make sure to keep it
out of their reach.Step 5. Locate the heater control valve. Most are near the firewall of the
vehicle on the passenger’s side of the vehicle. It will have heater hose
attached to both sides. The valve will have a cable attached to it for
Step 6. Loosen the clamps that attach the heater hose to the control valve.
NOTE: Some coolant will still be in the hose.Step 7. Once you remove the hose clamps, twist the rubber heater hose where it
attaches. Pliers usually make this job easier. While twisting, pull the hose
from the valve.Step 8. Once the heater hoses are removed, disconnect the heater valve control
cable.Step 9. OPTIONAL This is the perfect time to replace old or damaged heater hose.
If it appears to be original, is in poor condition, or is leaking, disconnect
the hose from the engine and replace it.Step 10. If you are reusing the original heater hose, make sure it is clean and
free of corrosion. Replace the old hose clamps by placing them on the heater
hose before installing the control valve.Step 11. Install the control valve cable on the new heater control valve and
fully push the heater hose on to the new valve.Step 12. Tighten the new hose clamps and refill both the radiator and overflow
bottle.Step 13. At this point, start the engine and turn the heater on high so the
valve is open and air can escape from the system.Step 14. Replace the radiator cap, allow the engine to warm up to operating
temperature, and check for leaks.Best Practices
- This is a good time to replace heater core hoses and clamps.
- Never work on a the cooling system when it is hot.
- Make sure the cable to the heater control valve is free and easy to move
before attaching it to the new control valve. If tight, try to lubricate it
or replace it.
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Article first published 2009-07-28 (Updated 2015-01-09)