Wildguzzi.com
General Category => General Discussion => Topic started by: Brooksr13 on March 18, 2015, 05:11:54 PM
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OK, So now in my continuing saga of silly events, I agreed to look at my cousins wife's 2002 California. She needed a new battery, new tires and had several oil leaks. Not being able to start it, I went and picked it up on my trailer and brought it home. First Mistake.
I then fixed all that was wrong with it and found several electrical issues that she had not known about. Burned out TS relay..etc.
Once I had it all ready to go, it of course fell off of my lift, bending the bars and breaking a mirror and clutch lever. Long story short......On the test ride after replacing all the bent parts I noticed that the Tach was not responding. I checked the wiring and all looks good, I took out the tach and connected it to my Centauro and it revs fine.
I'm kind of at a loss here. I have looked at the wiring diagram and it looks to me like if one of the wires were bad, several other things should be showing signs of not working.
Any ideas??
Mark
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No, but congratulations on having a cousin who's wife has a Guzzi.
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Yes that is unusual, he rides a Honda.
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Hmm , did any tachs of that era ever work for more than a month ? :o :D
Dusty
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Given the behavior of my instruments I agree, but in this case he's got a proven tach, it's just on the wrong bike.
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Given the behavior of my instruments I agree, but in this case he's got a proven tach, it's just on the wrong bike.
It's FM ;D Dunno . Bad ground seems to be a popular answer .
Dusty
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Well the Centauro Tach does not work on the California and the California tach works on the Centy so that seems to say that the Tach itself is ok.
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On my Stone the the instrument light bulb on the tach is yellow and the ground is black. The tach wire power positive is fed from the neutral/other bulbs/ lights and the negative wire is yellow/black going to the ECU. Mike
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If the starter button sticks in my centauro tach will not work.
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None of the wiring was changed when this occurred so i am pretty sure that isn't the issue. also the starter button is not stuck and returns when pressed.
Mark
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None of the wiring was changed when this occurred so i am pretty sure that isn't the issue. also the starter button is not stuck and returns when pressed.
Mark
May have missed it , was the tach working on the EV before the tip over ?
Dusty
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Unknown, so i kind of feel responsible for it. I'm thinking that the Tach is good since it runs fine on my Centauro. Just not sure where to start looking electrically on the California.
Mark
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The two bulb wires do not run the tach so, check the negative wire(yellow/black) back to the ECU. Then check the positive wire for power. Compare what you have from your other bike that works. I would guess either no power (first), or no signal from the ECU probably not(but the wire could be damaged)since the bike runs. Mike
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I believe the yellow wire is strictly for the light bulb, black wirer is ground for light bulb and could also be ground for the tach. There is another wire (not sure of color) that goes back to the ECU (computer) which is the wire that drives the tach.
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You should have + - and a wire from the ECU (actually from somewhere else if it has the large P8 ECU)
I think it's a yellow wire with black stripe, it might be run outside the loom. You could probably run a new wire
to a coil terminal if you can't locate it.
I believe the Tach gets 12Volts from the headlight relay, is the light going?
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Both the Tach light and headlight are fine.
Yellow Wire goes to Tach Bulb
3 other wires are :
Yellow/Black -------> ECU
Black --------> Ground
Red/Green --------> looks to power all indicator bulbs and terminates at the Starter relay and start switch
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There is a mention of a Black wire with a ringed connector for another ground wire to the body of the tach on my Stone. I believe it goes on one of the rear studs. It was taped on bikes like my Stone that did not come originally with a tach. It was mentioned in the tach installation instructions. Could you be missing that second ground? I just don't remember that far back. Mike
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As mike says, there is a ground for the light and a Negative for the electronics, this is shown in the manual.
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Yes I have both grounds and they are good, I have power to the tach on the Red/Green wire.
If the Tach gets its signal from the ECU shouldn't I read voltage on the Black/Yellow wire???
Mark
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OK Here is what and how I have tested so far:
Both Grounds on the Tach show continuity between the connector on the Tach and the fin on the Voltage Regulator
When the Key is turned on, I read power on the Red/Green wire and the Tach light bulb lights up.
I unplugged the ECU, found the Yellow/Black wire in the plug and tested continuity between it and the Yellow/Black connector on the Tach harness.
What am I missing here???
Mark
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And just to make sure I was not crazy, I took the tach out of the California and put it on my Centauro and it works just fine.
So the tach is fine......
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Forget about the lamp supply, it is separate
The tach should have
Black wire on a negative terminal (not the one on the case, that's for the light)
A red/black wire +12 Volts from the headlight relay on a Positive terminal
Yellow/black pulses from the ECU on another terminal,
Which ECU do you have, the large P8 or smaller 15M
If you turn the key on and scratch a wire from the pulse input terminal onto + you should be able to get it to go upscale a little bit.
It's always possible the ECU pulse outputs fried.
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I think you have the 15M ECU. I do not know how to check the tach signal. But so far you seem to pointing towards the ECU being the problem. Mike
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Yeah, I'm coming to that conclusion. Before I started working on this bike, she had a completely dead battery and I know that she tried a number of times to jump start it using a car battery. Could that have blown the ECU?
Mark
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Find someone that has an oscilloscope that will do a signal trace for you. Maybe someone one at the local trades school?
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It's dead, Jim. :'(
Too soon?
I'm going with either the signal wire (which I thought was gray . . . where did I come up with that?) or the ecu signal. Is it getting a pulse generated by the ecu or does the ecu simply pass on the cam position sensor signal and the tach does x2?
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Signal Wire: Yellow/Black is good end to end...Just don't know if the ECU is producing a signal. Found many weird things electrically that were bad on the bike and wondering if trying to jump start a dead battery can cause damage to the electrical components. I could barely get the old battery out of the bike as the sides were swollen. I think she dodged a bullet as it didn't just burst on her.
Mark
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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
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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
Me, too..
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Can you explain, "Pick up the pulse from one coil" ?
Mark
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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? ???
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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.
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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 . . .
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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
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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.
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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.
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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
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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.
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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.