A few days ago, TWIKE 560 started acting weridly – on the center console the left three LED’s turned on if the main lights were switched on, the right-hand blinker would work, the left hand one not. However, if the lights were off, then both blinkers would work fine.
Every seasoned TWIKE pilot knows that this typically means one or more of the 12V fuses are blown and the center console typically – and oddly helpfully – shows which side of the TWIKE is affected by lighting the corresponding LEDs on the front panel. Looking at the TWIKE, this is easily confirmed.
The weird reaction is due to the fact that, unlike a car, TWIKE electronics actually switch the drain and not the source. This means that 12V is continuously available everywhere and ground is switched. Which is the reason why common anode LED’s – e.g. for the combined brake/lighting lamps – don’t work in a TWIKE.
Lucky me that in Switzerland another currently non-functional part of my TWIKE is seriously under-utilized: the horn. I believe that I’ve not used it for the last 3 years!
Unlike when I was driving TW560 across India – during those weeks, I used the horn constantly 🙂
This time, however, the problem was not solved by replacing a fuse, as there was no blown fuse to replace. Also the very unusual dimming of the parking lights was pointing to another problem that might be more serious.
There is only one way to find out what the problem is: diving into the innards of my TWIKE!
I get out my trusted long-distance repair set that contains all the tools necessary to repair most of the less serious problems a TWIKE might have…anywhere.
With the box open I start pulling out the light green Imbus tool to get access to the battery bay.
WARNING
Opening the battery bay exposes you to the dangers of >400V DC. This type of current and voltage kills silently and efficiently. If you’re not 110% sure what you’re doing and take the necessary precautions…PLEASE CONSIDER HAVING SOMEONE QUALIFIED DO THE JOB FOR YOU.
With the warnings out of the way, the place we want to go to today is the so-called AK-Rail. It’s the place most of the electrical connections of a TWIKE go to and you can imagine it to be the higher-voltage part of the TWIKE’s ICU.
Again, and I cannot stress this too much, this PCB is full of contacts and traces that carry either AC or DC voltages – both at deadly levels. Please stay safe.
The parts we’re now looking for are the MOSFET’s that control the lights. The obvious first suspects are VM4-7 but some measuring later, I was confused: all of these were working fine. Where else could the fault lie?
A while later, I started re-reading the descriptions I thought to myself – which other parts of the TWIKE aren’t working: Horn and weird and strange dimmed parking lights.
Tadaa: the horn MOSFET wasn’t the problem but VM3 … responsible for the parking lights was acting very strange: with very low loads it worked fine but as soon as there was just more than a few watts the current would collapse and stay there.
A simple soldering job later, we’re back in business! Everything is back to normal and I’ve learned something new.
I really enjoy being able to repair close to everything on a TWIKE – this is the hackability / sustainable engineering that I’m missing from most current products on the market!