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Heater Control Valve Replacement
 
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Pelican Technical Article:

Heater Control Valve Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$250

Talent:

*****

Tools:

Set of sockets, screwdrivers, multi-meter

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Heater valve, heater hoses, engine coolant

Hot Tip:

Work with a cool engine.

Performance Gain:

Heat will work again

Complementary Modification:

Change thermostat, flush cooling system.

BMW Z3 models are equipped with a climate control system or HVAC (called IHKA by BMW) that automatically controls cabin temperature once a temperature is set on the HVAC control head in the center dashboard. IHKA controls air-conditioning, heating, internal blower motor operation and numerous air outlets. The electronic IHKA control module governs the operations of the following components:

  • Heater valve in engine compartment - controls the flow of hot coolant to the heater core inside the IHKA housing underneath the center dashboard.
  • AC compressor in the engine compartment - driven by engine accessory belt.
  • Blower motor underneath the dashboard behind the glove compartment - motor speed modulated using the blower final stage.
  • Air outlets - electric stepper motors attached to vent flaps control the flow of fresh or recirculated cold and warm air to windshield, face-level vents and foot wells.
  • Engine cooling fan - IHKA microprocessor and engine control module (ECM) determine operation and speed of cooling fan.

The heater control valve controls the flow of hot coolant to the heater core in the IHKA housing under the dashboard. If your vehicle has no heat and the cooling system is properly bled, the valve may be faulty (stuck closed). You may also have a situation where the vehicle has heat all the time. This may be a valve that is stuck open. In this tech article, I will show you how to test and, if necessary, replace your heater control valve.

A quick check is to warm the vehicle up and then turn the heat ON; both heater hoses should be hot to the touch. If one hose is cool and the other is hot the solenoid is not allowing coolant flow. You could also have a bad signal to the valve; it is a two-wire circuit. Using a wiring diagram, you can identify the ground and battery positive feed to solenoid, and test for proper voltage when the heat is ON.

Do not remove the radiator or expansion tank cap or work on any other part of the cooling system while the engine is hot. Coolant or hot steam may escape and will scald you. To do any work on the cooling system, wait until the engine has cooled off.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

This photo shows the location of the heater control valve (green arrow).
Figure 1

This photo shows the location of the heater control valve (green arrow). It is located at the left side of the firewall, above the heater hoses.

To access the heater control valve, start by removing the E-box seal from the right side engine compartment.
Figure 2

To access the heater control valve, start by removing the E-box seal from the right side engine compartment. (green arrow)

Then, unclip the plastic harness retainer.
Figure 3

Then, unclip the plastic harness retainer. There are a total of eight clips (green arrows). Four are shown here, the other four are on the opposite side of the panel. Once unclipped, remove the retainer from the E-box by lifting it up.

Now, you can remove the wiring harnesses from the mounting points.
Figure 4

Now, you can remove the wiring harnesses from the mounting points. This will allow the plastic junction above the valve cover to be moved out of your way.

Next, remove the two 10mm nuts (green arrows) for the wiring harness junction mount.
Figure 5

Next, remove the two 10mm nuts (green arrows) for the wiring harness junction mount. Then remove the mount from the firewall.

Working at the right side bulkhead, cut the wire tie securing the harness to the firewall.
Figure 6

Working at the right side bulkhead, cut the wire tie securing the harness to the firewall.

Using a bungee cord or rope, pull the plastic junction toward the radiator support and out of your way.
Figure 7

Using a bungee cord or rope, pull the plastic junction toward the radiator support and out of your way. 

Replacing the heater control valve - Drain cooling system. See our tech article on cooling system draining and filling.
Figure 8

Replacing the heater control valve - Drain cooling system. See our tech article on cooling system draining and filling. Working at the heater control valve. Squeeze both release tabs and pull the connector straight off to remove.

Then, pull the heater valve out of the mount.
Figure 9

Then, pull the heater valve out of the mount. Pull the bottom out first, then remove the top pin from the rubber grommet. Be careful not to lose the rubber mounting pieces, if you do, replace them with new ones.

Loosen both heater hoses from the heater valve.
Figure 10

Loosen both heater hoses from the heater valve. (green arrows) Then, remove the hoses from the valve. Remove the heater valve from the vehicle and install the hoses on the new one. Then install into the mount and connect the electrical connector. Once the valve is installed, install the wiring harness and replace the cut zip ties. Install the hoses and tighten the fasteners. If needed, replace the coolant hoses.


Install the intake manifold and other items.

Fill and bleed cooling system. Once complete, double check all the hose connections and check engine for coolant leaks. Testing the heater control valve

The heater control valve is normally open (allowing coolant to flow to the heater core) and closed when the temp setting is on COLD.
Figure 11

Testing the heater control valve -  The heater control valve is normally open (allowing coolant to flow to the heater core) and closed when the temp setting is on COLD. There is a small plunger (green arrow) that seals the valve when the solenoid receives the correct electrical signal. This plunger can become restricted, reducing coolant flow. The electrical portion can also fail, creating a situation where you have heat all the time.

The inlet for the heater control valve is on the top.
Figure 12

The inlet for the heater control valve is on the top. (red arrows). Hot coolant flows from the engine crankcase to the valve. It then flows through the valve out the bottom to the heater core (green arrow). A quick check would be to confirm hot coolant is entering the valve at the upper hose (red arrows) and into the heater core through the lower hose (green arrow). The following steps will show you how to test the electrical signal to the valve. If you do not have coolant flow through the valve, and the voltage is correct, replace the valve.

Working at the heater control valve.
Figure 13

Working at the heater control valve. Squeeze both release tabs and pull the connector straight off to remove.

On my vehicle the brown wire is a constant ground and the blue wire is the battery volt control from the HVAC control head.
Figure 14

On my vehicle the brown wire is a constant ground and the blue wire is the battery volt control from the HVAC control head. To test the signal to the valve, I will connect a digital volt meter across the terminals and test the voltage.

Start by rotating the HVAC temperature control to full hot (green arrow).
Figure 15

Start by rotating the HVAC temperature control to full hot (green arrow). Then turn the ignition to the RUN position.

Then connect your DVOM across the terminals, your DVOM should read Zero volts.
Figure 16

Then connect your DVOM across the terminals, your DVOM should read Zero volts.

Next, rotate the HVAC temperature control to full cold (green arrow).
Figure 17

Next, rotate the HVAC temperature control to full cold (green arrow). Ignition in the RUN position.

Your DVOM across the terminals, your DVOM should read BATTERY volts.
Figure 18

Your DVOM across the terminals, your DVOM should read BATTERY volts. These steps show a properly working circuit. If you are missing a voltage signal, check that the ground to the valve is good. Then check the battery volts signal back to the HVAC control head.


When done, reassemble items and confirm wiring is routed as it was before.

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Page last updated: Fri 12/9/2016 02:07:09 AM