Suppressing automotive voltage spikes

Thread Starter


Joined Dec 15, 2014
Hey guys,
My motorcycle is known to have this problem where the ignition coil can fail in a way that sends a very high voltage spike through the electronics and damages the ECU. The repair costs thousands of dollars.

When I connect a scope to my bike's battery with the engine running, I see a constant 14V with occasional transient spikes to 40-70VDC. I believe this is normal for an automotive power system, but it got me thinking. Would it be possible to place a device in the bike's electrical system (across the battery?) that would absorb voltage spikes of this type as well as in the case of a coil failure? Perhaps some type of TVS diode? Where would the device have to be placed in order to protect the entire system?

Thank you :)


Joined Nov 30, 2010
Nobody can tell you how to protect every part of an electrical system based on no information except, "It's a motorcycle."
Even if you come back with a make, model, and wiring diagram, it's still a major job to figure out every possible failure mode.
I think designing a spark coil that can fire into the ECU and destroy it is a bad design, but then, I think a car with 12 computers in it is a bad design, so don't believe me if you don't want to. I'd sell the car if I didn't think they all have a mass of unnecessary computers in them nowadays. You can still sell the motorcycle and get an old one without all the sensitive electronic systems designed for maximum Dealership profits.


Joined Jun 19, 2012
The trend to make everything digital and over complicated has it's hidden cost.

It's impossible to protect modern electronics from every possible source of damage, expect more unexpected failures.


Joined Nov 30, 2010
Seriously, I bought a 2005 Ford Explorer. Every MCU in it except the PCM and the transmission controller had failures, and that's about 8 of them.
Being an electronics nerd, I simply disabled most of them. My motto about cars: I owned a 1948 Ford pick-up truck and it had everything I need except air conditioning. Why my present car needs 12 computers, I will never know.


Joined Apr 9, 2013
Best way to protect for spikes is to clamp at the source, That will imply you install a TVS rated at least 18V at the ignition coil input, in parallel with the coil.
To make your life easier (no worries about polarity) I would suggest a bipolar TVS. Power dissipation of the TVS shall be in the range of 1500W.