Glow Plug Control Unit Relay – BMW (12217786821) Diesel Relay

The glow plug control unit relay (OEM 12217786821) is a vital engine electrical component designed to manage and regulate the current delivered to the glow plugs on diesel-powered BMW and MINI vehicles. This relay ensures each glow plug receives the correct electrical power and timing during cold start cycles, enabling efficient pre-heating of the combustion chambers for smoother and more reliable cold starts. A faulty glow plug control unit can lead to hard starts, extended crank times, irregular idle, and glow plug warning lights. Replacing a failing relay with a high-quality unit helps restore dependable diesel start-up performance and supports overall engine reliability.

OEM Number: 12217788327, 12217801201, 7788327

Operating Mode : Electric

Voltage : 12V

Number of Cylinders : 6 for left-hand/right-hand drive vehicles

Number of connectors : 2

Number of Pins : 1+12

Quantity : 1

Our SKU: TB12217801201_313

All our Glow Plug Control Unit Relay For BMW 12217786821 are OEM quality and reliable after market car parts. This Glow Plug Control Unit Relay For BMW 12217786821 is specifically compatible with BMW: 3 Series, 5 Series, 6 Series, 7 Series, X3, X5, X6, .

Please use our make-model-year tool to check this part's compatibility with your vehicle. However, please note that our tool is for reference only and we recommend that you check the part number on your old unit prior to purchasing.

If you are still not sure about the compatibility of this part to your vehicle, please supply us with the VIN number or Reg number in our live chat or contact form! You can also find details on our purchasing & shipping guide here.

Key Benefits

Precise Control of Glow Plug Power
Regulates electrical current and timing to the glow plugs, ensuring effective pre-heating of cylinder combustion chambers for improved cold starts.

Direct Replacement for OEM 12217786821
Designed to match BMW’s original specification, this relay replaces the factory part 12217786821 and related references such as 12217801200 / 7786821 / 7801200 without modification.

Restores Reliable Engine Start-Up
Replacing a defective relay can eliminate difficult starts, reduce crank time in low temperatures, and help minimise white smoke during engine start-up. 

Supports Diesel Engine Efficiency
Accurate glow plug timing promotes more complete combustion immediately after start-up, which can improve fuel economy and reduce emissions associated with improper ignition.

Compatible with Multiple BMW Models
Commonly used on a range of 4-cylinder diesel BMW and MINI applications, including E87 1 Series, E46 3 Series, E90/E91 and similar chassis with M47/N47 engines when matched to the correct part number.

Frequently Asked Questions (FAQs)

Q: What does the glow plug control unit relay do?
A glow plug control unit relay regulates the electrical current and activation timing sent to the glow plugs based on signals from the engine management system. This ensures the glow plugs heat up correctly before engine start, which improves combustion and reduces starting strain.

Q: What are symptoms of a faulty glow plug control relay?
Common symptoms include difficult cold starts, long crank times, glow plug/engine warning lights, uneven idle shortly after start, and increased white smoke at start-up. These often indicate inadequate glow plug heating or relay malfunction. 

Q: Is this a direct replacement for the original part?
Yes. This glow plug control unit relay is designed to replace the original OEM part 12217786821 and related references without requiring modifications, provided the vehicle’s engine code and part fitment match.

Q: Which vehicles commonly use this relay?
This relay is typically fitted to BMW and MINI diesel engines such as the M47 and N47 series used in various 1 Series, 3 Series, and X-Series models. Always check your VIN or existing part number to confirm correct fitment.

Q: Do I need professional installation?
While installation is generally straightforward for experienced technicians, professional fitting is recommended to ensure correct electrical connections and avoid triggering diagnostic fault codes.