BMW E28 heater not regulating? Heater control valve 64111373188
Short answer: If the BMW 5 Series E28 (M10, M20 or diesel M21) heats at full blast all the time, reacts sluggishly to the temperature control or the heater goes cold at higher revs, the heater control valve 64 11 1 373 188 (Bosch 1 147 412 008) is often the cause – due to a ruptured diaphragm or an interrupted solenoid coil. The solution is a remanufactured genuine valve, tested for leak-tightness, flow and switching function, for 269,00 €.
The temperature control is set to cold, yet the E28 still blows warm air into the cabin. Or the other way round: at idle at the traffic light it gets pleasantly warm, on the country road the interior cools down again. On the BMW 5 Series E28 with air conditioning and automatic heater control, a solenoid valve in the engine bay controls how much hot coolant flows to the heater core. After more than 35 years, this valve is a typical candidate for control problems. This guide shows how to tell the heater control valve apart from other causes, how to test it yourself and which part number fits your car.
Symptoms
The valve is open when de-energized and is controlled by the heater controller: in the cold position it is energized and closed, in the warm position de-energized and open. This results in typical fault patterns:
| Symptom | Likely cause |
|---|---|
| Heater stays warm all the time, even in the cold position | Solenoid coil interrupted or no control signal – the valve stays open |
| Heater responds sluggishly or imprecisely to the temperature control | Valve no longer switches cleanly, deposits or worn seals |
| Heat at idle, heater core goes cold at higher revs | Ruptured diaphragm in the heater control valve |
| Coolant loss, damp spot on the bulkhead in the engine bay | Leak at the valve housing or at the connections |
| Heater weak at standstill, warm while driving (cars with air conditioning) | More likely the auxiliary water pump of the same assembly – the test principle is shown in our guide to the Auxiliary water pump (circulation pump) at the heater control valve |
Causes
The heater control valve sits in the engine bay on the bulkhead on a bracket, directly in the heater water line to the heater core. It is therefore constantly exposed to hot coolant, pressure fluctuations and engine heat. Over decades the diaphragm and seals harden, and limescale and corrosion residue from old coolant settle in the valve seat. The diaphragm eventually ruptures, and the valve no longer regulates the flow cleanly. The Bosch solenoid coil ages from the constant temperature changes; if the winding wire breaks, the valve stays open permanently.
The operating principle is similar on many classics of this era – Mercedes also uses Bosch solenoid valves in the heater. If you drive a W124 or W126, you will find the differences in the guide to the Mercedes duo valve.
Testing it yourself
- Visual inspection: Engine cold, hood open. Check the valve on the bulkhead and the hose connections for traces of coolant, crusts or damp spots. Check the coolant level in the expansion tank.
- Hose test: Let the engine warm up, set the controller to cold. The hose behind the valve toward the heater core should stay noticeably cooler. Then turn to warm – after a short time it must get hot. Caution around hot parts.
- Unplug the connector: With the engine warm, pull off the electrical connector at the valve. Since the valve is open when de-energized, the heater must now heat at full power. If no heat comes, the flow is disrupted (diaphragm, deposits) or the cause lies in the cooling circuit.
- Check the valve control: In the controller's cold position, voltage must be present at the connector. If voltage is present and the valve still does not close, the coil or the mechanics are defective. If there is no voltage, the fault lies with the heater controller or in the wiring.
- Rev test: If the heater gets warm at idle and cold at higher revs, this clearly points to a ruptured diaphragm in the valve.
Solution
A valve with a ruptured diaphragm or interrupted coil cannot be saved permanently by flushing. The safe solution is replacement with an overhauled genuine part. The genuine BMW heater control valve 64 11 1 373 188 from Behr with Bosch solenoid part (Bosch 1 147 412 008, Behr 90.944.01.109) is completely disassembled, cleaned and fitted with new seals at our shop. This is followed by a leak test, a flow test and a switching test of the solenoid valve. The complete valve with housing is sold, not just the valve insert. The refurbished part comes with a 5-year warranty. The previous BMW number 64 11 1 368 637 has been superseded by 64 11 1 373 188.
BMW heater control valve 64111373188 – remanufactured
Bosch 1 147 412 008 · Tested for leak-tightness, flow and switching function
For 5 Series E28 with M10, M20 and M21
269,00 €
To the heater control valveCaution, risk of mix-ups: The E28 with six-cylinder M30 (525i, 528i, 533i, 535i, M535i, M5) and the 6 Series E24 have the valve 64 11 1 373 191 with a different position of the water connections. The dual valve of the 7 Series E32 and 5 Series E34 is a different part, as is the small valve type 64 21 1 368 650 with white elbow. Compare the number on your valve before buying. You will find all overhauled valves in the collection Heater valves & duo valves, more classic parts from other makes under Other makes.
Compatible vehicles
According to the BMW parts catalog for vehicles with A/C and automatic heater control. Please compare the number on your own valve.
| Model series | Models (engine) |
|---|---|
| BMW 5 Series E28 sedan (1981–1987) | 518 (M10), 518i (M10), 520i (M20), 525e (M20), 524d (M21), 524td (M21) |
| BMW 5 Series E28 US version | 528e (M20), 524td (M21) |
| Does not fit | E28 525i, 528i, 533i, 535i, M535i, M5 (64 11 1 373 191) · 6 Series E24 · 7 Series E32 · 5 Series E34 |
FAQ
Does the heater control valve 64111373188 also fit an E28 525i or 528i?
No. The E28 with six-cylinder M30 (525i, 528i, 533i, 535i, M535i, M5) and the 6 Series E24 have the valve 64 11 1 373 191 with a different position of the water connections. According to the BMW parts catalog, the valve 64 11 1 373 188 is intended for E28 with M10, M20 and M21.
Is the heater control valve in the BMW E28 open or closed when de-energized?
Open when de-energized. In the controller's cold position the valve is energized and closes, in the warm position it is de-energized and open – the heater then runs at full power. If the coil is interrupted, the valve stays open and the heater heats permanently.
Why does the heater go cold at higher revs?
A ruptured diaphragm in the valve is typical. At idle some heat still reaches the heater core; as coolant pressure rises at higher revs, the flow is disrupted and the heater core cools down.
Does the valve also fit a BMW 7 Series E32 or 5 Series E34?
No. The E32 and E34 use a dual valve, which is a different part. The small valve type 64 21 1 368 650 with white elbow is not equivalent either.
How much does the overhauled heater control valve 64111373188 cost?
The remanufactured genuine heater control valve 64111373188 (Bosch 1 147 412 008, Behr 90.944.01.109) costs 269,00 Euro per piece. It was completely disassembled, cleaned, fitted with new seals and tested for leak-tightness, flow and switching function; the refurbished part comes with a 5-year warranty.
KFZTeile-Thot is a specialist business for tested and refurbished Mercedes parts with its own test benches – and with the same care also refurbishes tested classic parts of other makes such as this BMW heater control valve. Every valve is individually tested before shipping, and over 1,000 positive eBay reviews reflect this. Not sure which heater control valve is installed in your E28? Call us at +49 179 8991069 (Mon–Fri 8 am–6 pm) or write via our contact form – fastest with your VIN (chassis number) and model year; we check the fit free of charge.