Is the heater control in your BMW 2002 stuck? Or does the control operate sluggishly, never quite turning the heater fully on or off? It's time for a new heater temperature control valve.

In temperate climates such as ours, the heater is used only a few months per year. Sitting idle for so long, the valve can easily become fouled with grit and sludge. The plastic valve element in my car was scored by grit, just enough so that it couldn't quite stop the coolant flow. A Bavarian sauna!

Tools and parts required:

  • Heater temperature control valve
  • (2) short 7-mm wrenches
  • Short 8-mm wrench
  • (2) 1.5" hose clamps
  • Small pocket mirror

Degree of difficulty: Intermediate

First, determine that the valve is indeed the problem. The valve is located in the drain trough on the firewall just in front of the windshield on the passenger's side. It is tucked up under a welded plate to insure maximum frustration in getting to it. The side facing outwards is a cover plate, held in place by two wide screws. The other side looks like the accompanying sketch. You can place a small mirror in the trough up against the blower motor as an aid. Remove the 7-mm self-tapping bolt holding the actuator arm to the valve shaft and check the Bowden cable for free movement. Do not detach the cable from the arm it's a bear to reconnect. Only small wrenches (or a ratchet with flex extensions) will fit in the workspace. I used a MAFAC tool kit designed for 10 speed bikes. Coolant leaks around the valve or a freely-moving cable indicate a malfunctioning valve.

Drain the cooling system to prevent spillage when you remove the valve. Remove the 8-mm bolts holding the valve to its support bracket on the heater box. Loosen the hose clamps and remove the valve. Discard the cotter-pinned "sardine can" clamps they will be replaced by more manageable hose clamps upon re-assembly.

Install the new valve and hose clamps, being sure that the direction arrow on the valve body points into the passenger compartment. Install the 8-mm bolts which hold the valve to its support bracket on the heater box. Install the actuator arm on the valve shaft's end. Don't over-tighten the 7-mm self-tapping bolt it goes into soft plastic. Tighten all hose clamps. Finally, top up the coolant and run the engine to check for leaks and for proper heater control range. If necessary, adjust the control range at the Bowden cable clamp on the actuator arm. This is a drilled-bolt and nut combination, both 7-mm.

How can you prevent repetitions of heater control valve failure? Flush your cooling system regularly, use a good water pump lube with your coolant and, most important, exercise the valve. With the engine warmed up, turn on the heater for a few minutes every week A little care pays off.

Author: Terry Shankland