Customers issue on this 2018 mk1 BMW i3: Intermittently no heat output into cabin of vehicle

Firstly we carried out a functions test on all interior heater controls and the customers’ issue was quickly confirmed. Good news for us as intermittent faults are quite often the most difficult to diagnose! There were no warning lights on or other faults reported.

After this we carried out a full vehicle system report, which will show us any fault codes in areas where the electronic systems have recognised there may be issues. Being an EV it is also crucial for us to know if there are any high voltage isolation fault codes logged in any onboard modules.

Fault codes logged:

801380 EDH: Internal Error

E70C3A Electric Auxiliary Heater: Does not respond

A conventional internal combustion engine’s (ICE) heating system utilises the heat produced by the engine to produce the heated air inside the cabin. This is achieved by a mechanical water pump pushing cooled coolant through the engine where it is heated and then into the heater matrix inside the car.

The BMW I3 uses a high-voltage electric auxiliary heater which is separate from all other high-voltage components and in principle functions like an electrical flow heater. The coolant is pumped via a small low-voltage brushless water pump into the auxiliary heater and heated depending on the driver’s request and the in-car temperature. Unlike that of an ICE, the heating circuit is a stand-alone circuit purely for providing heat inside of the vehicle and although still using coolant, the system provides no cooling effect whatsoever. It does however provide anti-freezing down to -40 degrees C.

Using the manufacturers’ technical data and wiring diagrams we were able to identify this component and create a test plan.

All circuit tests were carried out on the high-voltage and low-voltage systems confirming the electric auxiliary heater was at fault. This would require the high-voltage system to be disabled to enable us to replace this part.

We discussed our findings with the customer who authorised the repair.

Repair day: The area was cordoned off and all other staff members were made aware of it for safety purposes.

The high voltage system was disabled via the service disconnect and locked.

This is confirmed via a message on the dash display.

The 12-volt system is also disconnected.

Wearing class 0 gloves and other relevant PPE the high voltage connector is removed from the the electric auxiliary heater.

We confirm the high voltage system is indeed off by testing for voltage on this connector.

We proceed to remove the heater from the car and compare it to the new one from BMW. (Although they are visually the same the new one is the revised part)

New electric auxiliary heater fitted and connected.

The BMW i3 heater circuit uses a very specific coolant.

The small coolant circuit does not have a means to bleed so it must be filled with a specialist vacuum filling tool. The vehicle must not be in ECO-PRO MODE when doing this!

The high-voltage system is safely reconnected, and the electric auxiliary heater is programmed with the latest software installed. All systems are once again checked and tested before returning the car to the customer.

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