Life with the Model S has been good. I’ve kept up with a pace of about 25,000 miles per year since I took delivery despite various life changes along the way and I’ve enjoyed almost every mile (the exceptions are the ones below).

Software updates on my 4-year-old Model S have slowed down quite a bit with few new features being added and the only recent service was for some new winter tires (same as before) after I wore out the first set. So there hasn’t been a lot to write about other than the wait on the Model 3 until some recent failures.

Power Degraded

I was heading down to visit my daughter in ConnecticutĀ for a quick trip and about half way there I got an alarming notice on my display:

This was on the highway, so I let the car slow down to 60 or so and then tried to accelerate back to 70 and it was painfully slow to get there. I did get back to 70 and could maintain that on the highway.

I called Tesla service and they said I should bring in the car as soon as possible. Meanwhile, they gave me a procedure to reset it. This essentially involves parking in a safe area and then doing a full power down of the car, then waiting 30 seconds then powering the car back on. This is all accessed from the display where you can also engage the emergency brake.

Since I was on the highway there was no convenient spot to do it and I was keeping speed fine so I just carried on for a while. Eventually, I hit traffic and got off the highway to go around it. I came to a stop off the exit to make a turn and then getting the car going again was very difficult. Each stop light and turn people were honking me for not moving quickly and I had it floored.

Fortunately, the terrain was fairly level, there was so little power that I’m not sure it would have gotten going again if I had hit a stop light on a hill.

I eventually got through the residential area and found a Dunkin Donuts to pull into and performed the procedure. For the rest of the day (another 100 miles on back roads and highways), the car worked fine.

The power reduced mode is so degraded as to be unsafe.

The next day I hit the same issue on the way to work. I went through the same reset procedure and made an appointment with Tesla for later in the week to get it fixed.

Root Cause

I dropped my car off at Tesla and got an ugly Range Rover gas guzzler for a loaner — this was my first non-Tesla loaner since I bought my Model S. The gas tank was less than half full and I live a long way from the service center so it meant pumping gas for the first time in a long time.

Tesla eventually diagnosed the issue:

Technician verified low coolant flow to Drive Inverter. Inspected coolant system and found internal fault with 4-way valve causing a leak. Replaced the 4-way valve and performed three coolant air purges. Verified no leaks after purges.


This fix was an inexpensive $137.25 (I’m out of warranty) but the issue was concerning.

To date, I’ve had all recommended services (annual) for my car and, while the Tesla has less moving parts than an ICE car, it seems there are still some unique parts other than suspension and tires that are wearing out and failing over time which can cause various unique issues.

It turns out this wasn’t the only issue I’d hit just shy of $100K miles. Stay tuned for the next (more expensive) failure.