Environmental Impact

December 15, 2009 | Reply More


With cold weather closing in upon us, your customer’s attention may turn toward comfortable warmth. The days are getting shorter, children have returned to school, and on cold mornings they’d better have heat in their BMW’s! Inform your customers that even in this hectic life we live they should still take the time to properly warm up their vehicles, which will extend engine life.  After a short warm-up they will not want to be feeling cold. BMW has advanced its climate-control systems to address the driver’s concerns, such as quickly defrosting the windshield and sufficient heat provided quickly.


This single heater control valve is mounted behind the auxiliary coolant pump. It determines how much coolant makes it to the heater core, and the auxiliary coolant pump assists flow when heating demand is high.

In previous issues of TechDrive, the air conditioning portion of the overall HVAC system was covered in depth. IHKS, IHKR and IHKA were reviewed, leaning toward A/C compressor operation and engine management system integration. Now, let’s turn our attention toward keeping our customers warm.

Controlling the blower motor speed is obviously important, and has advanced from simple parallel circuits with a matrix of resistors of different values to a more sophisticated solid-state module capable of many more speeds, and which can respond to changes in demand automatically.

It’s Getting Hot In Here


The final stage unit is usually located behind the glove box. The yellow wire with a green tracer is the power supply from the heater relay, the brown wire is ground, and the red wire with a green tracer is the power supply. The black wire with a green tracer is the ground supply to the blower motor, and, finally, the blue wire with a red tracer is the control wire from the IHKR or IHKA control units.

While the conventional thermostat and heater core have been supplying heat for passengers for decades, over the past 20 years BMW has improved its systems with the addition of an auxiliary water pump. With added heater cores for dual- and multiple-zone systems, coolant plumbing has become more complex. With this additional piping and sharper angles, coolant flow is often compromised.

To help maintain flow, the auxiliary coolant pump is used to maintain flow through the additional hoses whether the thermostat is open or closed. Also, it allows the coolant that is heated by the engine after start-up to quickly get circulated through the vehicle’s heater core(s). The auxiliary coolant pump is only activated when heating demand is high. The IHKS, IHKR, and IHKA control unit manages the operation of the pump when the interior temperature is approximately five deg. F. colder than the selected temperature.  The pump is typically mounted on the coolant return side of the heater core(s), sending coolant back to the water pump. This allows even coolant flow through each heater core even on multiple-zone temperature-controlled systems. The pump works in conjunction with a heater control valve.

The heater control valve has been used


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Category: BMW TechDrive

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