This is a full case study of a Porsche Taycan inverter replacement and electric motor repair carried out at our workshop in London. You will see exactly what failed, why it failed, and what the repair cost, so you understand what you are dealing with if your Taycan has broken down.
Table of Contents
- What Caused the Porsche Taycan Inverter to Fail?
- How the Fire Started Inside the Inverter
- Why Coolant Got Into the Electric Motor
- Step by Step: How We Carried Out This Repair
- Dropping the Battery and Rear Axle Assembly
- Replacing the Rear Electric Motor
- Opening the High Voltage Battery
- Programming the New Inverter and Getting the Taycan Ready
- Road Test Results and Final Checks
- Porsche Taycan Repair Cost Breakdown
- Frequently Asked Questions
- Conclusion
Your Porsche Taycan stalled completely while driving. No warning. Just stopped. You had it recovered and now someone is telling you the inverter is burnt, the electric motor is damaged, and the battery has a fault. It sounds like the car is finished.
It is not finished. But this is a big repair. The Porsche Taycan inverter replacement alone is not the end of the job. When we received this Taycan at our London workshop, what looked like one failed component turned into a full rear drivetrain and high voltage battery repair. This article explains exactly what we found, what we did, and what it cost.
What Caused the Porsche Taycan Inverter to Fail?
Root cause: the cooling system was not properly bled after previous work on the car.
This Taycan had been in an accident. Repairs were done. Coolant was drained and topped up. But the system was never bled correctly using the diagnostic procedure. Air pockets stayed in the cooling circuit. The cooling stopped working as it should. Heat built up. The inverter overheated and caught fire internally.
Here is the important point: no cooling components failed on this car. We did not replace a single pump, pipe, or valve as part of this repair. The original parts were all fine. The problem was that nobody ran the bleed procedure after the previous repair.
That one missing step cost the owner approximately £13,000 plus VAT.
How the Fire Started Inside the Inverter
The Porsche Taycan rear inverter has a cooling pad underneath it. Coolant runs through this pad to keep temperatures under control during driving. When the system is not bled, air pockets stop the coolant from flowing properly. The inverter gets too hot. In this case, it got hot enough to catch fire inside the unit.
When we removed the rear axle assembly and lifted it onto the work table, we could see the fire damage clearly. The inverter control unit was badly burned. A short circuit had happened between two of the high voltage phases. That short circuit sent a spike of current back through the system into the high voltage battery, where it blew a fuse and triggered a relay fault.
What looked like one broken part was actually a chain of failures, all starting from one uncleared air pocket in the cooling system.
Why Coolant Got Into the Electric Motor
Here is the part that changed everything about this repair.
When we lifted the rear motor and transmission assembly off the subframe, we found coolant inside the electric motor. This should not be there. The cooling circuit and the electric circuit must stay completely separate.
What happened: the heat from the inverter fire caused the cooling pad to fail. Coolant leaked from the pad, ran into the inverter, and then down into the electric motor.
We tested it immediately with an isolation test. The needle went to zero. The motor was finished. Replacing only the inverter and putting everything back together would have achieved nothing. We needed a new electric motor too.
Step by Step: How We Carried Out This Repair
This is not a simple job. To access the rear inverter on a Porsche Taycan, you cannot just unbolt it from above. The assembly design means you have to remove multiple major components first.
| Stage | What We Did |
|---|---|
| 1 | Dropped the high voltage battery to gain access to the rear subframe |
| 2 | Stripped the rear suspension and drive shafts |
| 3 | Removed the full rear axle, motor and transmission assembly |
| 4 | Separated the motor from the transmission |
| 5 | Replaced the electric motor with a donor unit |
| 6 | Installed the new inverter |
| 7 | Reassembled the full rear drivetrain |
| 8 | Opened the HV battery safety box and replaced blown fuse and faulty relay |
| 9 | Reprogrammed the inverter (two-stage: operational + immobiliser) |
| 10 | Bled the cooling system using diagnostic tool |
| 11 | Road tested 50 miles with live temperature monitoring |
Dropping the Battery and Rear Axle Assembly
The design of the Porsche Taycan rear drivetrain is interesting. The motor and transmission assembly does not connect directly to the subframe. It connects to the car body. The subframe also connects to the body. And the front mountings of the motor connect through a bracket that is attached to the battery.
This means you cannot remove the subframe alone. You cannot remove the motor alone. They all come out together as a system. The battery has to come out first to free the motor’s front mountings.
We used a specialist lift table to lower the battery safely. Then we dropped the complete rear axle assembly, keeping it in position while we swapped the work table underneath it.
Replacing the Rear Electric Motor
We sourced a donor rear motor. Before fitting it, we checked the part numbers. There was a one-letter difference in the part number compared to the original. On some Porsche components, one letter can mean a different gear ratio. We investigated and confirmed the motor was compatible. We did not take chances.
One thing worth mentioning: the Porsche Taycan electric motor is not a dry motor. Most EV motors have no internal oil. This one does. It has oil inside the housing for lubrication and cooling. This oil works alongside the external water cooling circuit. We checked the donor motor’s internal oil. It was clean and the correct colour.
We separated the motor from the transmission, fitted the new motor with the correct silicon grease on the O-ring seal, and reassembled the unit before installing the new inverter.
Opening the High Voltage Battery – the Blown Fuse and Faulty Relay
After programming the new inverter, the car still would not go ready. There was a fault code pointing to the high voltage battery’s internal safety box.
We dropped the battery again. A second time. This was not something we planned, but there was no other way.
Inside the safety box, we found the power relays and fuses. These are not standard fuses. They trigger ten times faster than a normal fuse to protect the battery cells from short circuit damage.
We did a resistance check on each:
- Fuse 1: good
- Fuse 2: blown
- Relay: faulty (sticking)
These faults were caused by the short circuit from the inverter fire sending an overcurrent spike into the battery. We replaced the fuse and the relay, reassembled the safety box, and reinstalled the battery.
Programming the New Inverter and Getting the Taycan Ready
A new Porsche Taycan inverter is not plug and play. It needs programming. And it is a two-stage process:
- Operational programming – this aligns the inverter with the car’s control systems. Takes approximately 6 minutes but requires a stable supply voltage of at least 13.6 volts.
- Immobiliser programming – the Taycan immobiliser is integrated into the rear inverter. Programming it involves placing the key in a specific position, just like programming a new key to the car.
After both stages were complete, we ran the full diagnostic bleed procedure for the cooling system. This is a 30-minute procedure where the car’s own pumps and valves cycle through a set sequence to push all air out of the system. It is not optional. It requires the diagnostic tool.
The 12V battery was also discharged when the car arrived. We sent it to our colleagues at Car Keys Solutions in Watford who charged and reset the battery control unit. This saved the cost of a replacement 12V battery.
Road Test Results and Final Checks
Before the car went on the road, we found several other issues. Some were from the original accident. Some were new.
- Wiper motor failure – caused by a voltage surge from the low 12V battery. The control unit inside the motor did not survive. We replaced it.
- Air suspension connector – a lower connector on one rear air spring had come loose. Reconnected.
- Crash sensor wiring – the front crash sensor connector was broken, left over from the original accident repair.
- AC system – only 140g of refrigerant found. Should be 850g. We flushed, vacuumed, and regassed the system.
- Coolant hose clips – two clips were not properly secured and one pipe was routed incorrectly from the previous repair.
| Component | Temperature Recorded | Expected Range |
|---|---|---|
| Rear inverter board | 33-44 degrees C | Under 70 degrees C |
| Battery cells | 17 degrees C | 17-40 degrees C (cold day) |
| Battery cell balance | Even across all cells | Even |
| Battery state of health | 100% | Expected at 14,800 miles |
Table 2: Road test temperature readings, Porsche Taycan, OGS EV & Hybrid Repair, 2025.
Porsche Taycan Repair Cost Breakdown
| Item | Approximate Cost |
|---|---|
| Rear inverter (new, dealer part, supplied by customer) | £3,000 – £4,000 + VAT |
| Rear electric motor (sourced separately) | £3,000 + VAT |
| HV battery fuse + relay | Included in parts total |
| Wiper motor + misc parts, fluids, consumables | Approx £1,000 |
| TOTAL PARTS | Approx £7,000 – £8,000 + VAT |
| LABOUR (full repair, all stages) | £5,500 + VAT |
| TOTAL | Approx £12,500 – £13,500 + VAT |
Table 3: Repair cost summary, Porsche Taycan, OGS EV & Hybrid Repair, London, 2025. Costs approximate; VAT additional.
Frequently Asked Questions
What causes a Porsche Taycan inverter to fail?
How much does a Porsche Taycan inverter replacement cost in London?
Can a Porsche Taycan be repaired by an independent specialist instead of a Porsche dealer?
What happens if coolant gets into a Taycan electric motor?
Why does the Porsche Taycan need the battery and rear axle removed to replace the inverter?
What is the high voltage battery safety box on a Porsche Taycan?
Does the Porsche Taycan electric motor have oil inside it?
How long does a Porsche Taycan inverter replacement take at an independent workshop?
Can the Porsche Taycan cooling system bleed be done without a diagnostic tool?
Why did the wiper motor fail during this Taycan repair?
Conclusion
A Porsche Taycan inverter replacement is one of the most complex EV repairs you can have. It is not just one part. It almost always involves the rear axle assembly, the battery, the electric motor, and the high voltage safety components inside the battery. In this real case at OGS EV & Hybrid Repair in London, the total repair cost came to approximately £13,000 plus VAT.
The cause was simple. The cooling system was not bled after a previous repair. That was the only mistake. But on an electric car with a thermal management system this complex, that mistake is enough to take out the inverter, the electric motor, and components inside the high voltage battery.
If your Taycan has stalled, thrown multiple fault codes, or you can see any sign of smoke or fire near the rear axle area, bring it to a specialist who can carry out a full diagnostic. The sooner the fault is found, the less damage spreads.
We at OGS EV & Hybrid Repair carry out Porsche Taycan independent specialist repair in London, including inverter replacement, electric motor repair, high voltage battery fault diagnosis, and full cooling system restoration.
