What is "Power Transistor"?

[JM2]

Greetings.

The hms online manual ignition troubleshooting chart lists 'faulty power transistor' as a cause of not starting. I have not seen that mentioned in any of the posts I've read. What is it? -Thanks.

[Barnyspup]

There are 2 Coils which supply spark. The spark occurs when the current to the coil is switched Off. This is under control of the ECM (Engine Control Module) using the various sensors to determine exactly when to switch the coil Off.

The coil windings carry a hefty current and so it takes a special high current power transistor to be able to do the switching.
Those power transistors are buried deep within the ECM and aren't a DIY replacement item.

I suspect maybe the technical writer for the manual merely threw the info in on a whim.


Jim

[JM2]

Thanks, Jim. I've been reading posts all afternoon and have found yours to be especially helpful.

You posted a pic called 'engine control relay.gif'. Would that be the same relay that others call 'main engine relay (under the dash)'?

[Barnyspup]

"Engine Control Relay" is the Hyundai designation, but I suppose Main Engine Relay would fit as well.

My simplified diagram below shows the function of the relay.

(My initials would be JM1)