2002 California EV Tachometer is Dead

[StuCorpe]

Just curious, could you use a multimeter with Frequency readout to check the output of the ECU?  I have a elcheapo Fluke and an off brand that both have frequency up to 10 MHz and have never tried using them for this.  Anyone else tried it? ???

[rodekyll]

I think the 15M ECU must generate a nice square pulse for the tach, My 78 with the P8 gets a pulse from elsewhere.

Do you have another bike you can try the ECU in, see if the tach works in it?

You say in your first post the bike is running so I doubt the ECU was damaged by jump starting, they have a safety diode that protects it from reverse voltage.

If it turns out the ECU output is not pulsing I would be tempted to try picking up a pulse from one coil

A coil or magnet pickup was what I was thinking when I asked how the signal is formed.  I've drilled a little hole into my flywheel and JB welded a .3" round magnet in it.  I'm hoping a hall effect sensor glued into the timing inspection plug will tell my tach what's up.

A coil pickup would be made by simply running a wire from the sensor pickup on the tach down to the plug wire, somewhere near the plug itself.  Just wrap the wire 3-8x around the spark plug wire.  It does not have to be 'tight'.  You can wrap some electrical tape around the last wrap on the wire to hold it there.  I have some special wire for that -- about 16ga, and very fine, limp strands of a silver-looking wire.  I've done it with fine strand copper wire, too.  I think the key is more wire gauge and strand size (= number of strands in a given gauge) than the strand material, but that's just a guess.

A coil pickup is a mod that needs to be 'tuned' for the individual bike.  If you get any signal from your initial wraps, it's encouraging.  Then you just need to find the sweet spot on the spark plug cable and the right number of wraps for a stable signal.  If the needle is jumpy or starts swinging wildly at some rpm, an adjustment to the position or #wraps is in order.

[rodekyll]

I'm plumbing in my efi wiring on the trike -- same harness as you use.  The tach wire has a single bullet connector that lives a few inches from the injector plugs.  I forgot about it.  It's an odd connector.  I've done perfect matings of the two plug parts and due to the design, missed the male/female coupling of the wire completely.  I mean -- it looks perfect but didn't connect.  Your problem could be that easy . . .

[Brooksr13]

OK a few more clues and tests....

I noticed that the High beam was not working and went into the headlight shell to investigate. The shell was filled with burnt plastic from the connector to the bulb and the wire to the High beam was fried. I clipped the wires and attched another socket and replaced the blown bulb.  Something got very hot in there at one time.

Back to the Tach.  I removed the center wire (Black-Ground) and ran a jumper directly from the Center connector on the Tach to the Battery (-)   No Change

I replaced the ground wire and ran a wire from the + terminal on the Tach directly to the Battery (+)  No Change

Is it possible that the ECU is running just fine except for sending out a signal to the Tach on the Black and Yellow wire????


Mark

[Kiwi_Roy]

Is it possible that the ECU is running just fine except for sending out a signal to the Tach on the Black and Yellow wire????

Yes, I'm sure I mentioned that (reply #21 & #27)

I haven't tried picking up off the high tension lead as Rodekyll mentioned but it should work. I was thinking more of connecting to one of the primary wires. For the pair of coils you have a common 12 Volt feed (same colour on both coils) and a different colour for each coil, Tap into either of the latter, for a test poke a sewing pin through the wire that way if it doesn't work the impact on the wire is minimal.

[Kiwi Dave]

Is it possible that the ECU is running just fine except for sending out a signal to the Tach on the Black and Yellow wire????


Mark

Exactly what I was thinking.  Easy way to eliminate would be to borrow someone else's ECU of a similar model (It's a Magneti Marelli IAW 15M, most California's this century except the Vintage).  One of the easier ones to get at, behind the LH side cover.

[Brooksr13]

Yeah, I have been looking for one for a while, neither of the two local shops have a spare and of course will not just let me "try" one.

Mark

[Kiwi Dave]

Run a wire directly from the ECU terminal to the appropriate place on the tachometer (after removing the existing wire).  If the tach now works, then the ECU is OK and there's something amiss in the wiring.  If it doesn't, and you've tested the tach on another bike, it's gotta be the ECU.

[Brooksr13]

Yes I have done that.....Tis the ECU it seems.  That Tach runs just fine on my Centauro.  Now off to find a used 15M ECU.