Tachometer is dead

Hello all, I am hoping to get some insight into trouble shooting my tachometer. I have a 1998 with 18k miles.

The story starts with a new stator that I installed for my friend last fall. He had been having dead battery problems and he guessed it was the stator. To be honest I was a bit put out because he was asking me to "help" fix it - which translated into me doing all the work and him watching.. He's an old friend so I knew what I was getting into. The fix went well, though he never took it out again, fast forward 6 months and my friend passed away and I have inherited the bike.
So I did a bunch of basic stuff, cleaning, new chain and sprockets, fluids, I took it out a a few rides, nothing too long as I didn't have papers for it yet. Finally got the tags two weeks ago when the DMV reopened. My first day out the bike cut off, I lifted the seat to find a bulging battery and a blown FI/fuel pump fuse.
I got a new gel battery and hoped to start it up to test everything, but it immediately would blow that fuel pump fuse. After the relays tested good I figured it was the ECU, that arrived today and solved the fuse blowing. The bike fires up, the stator still works and the new regulator is wired up.
Two things I noticed, both the headlight bulbs had burned out - replaced those and they now work fine.
The major problem now is that the tachometer does not work, all the other gauges are good - though I have not ridden it yet to test the speedometer. I tested the yellow wire at the instrument cluster connector against the ground and got about 3 or 4 volts at idle then it shot up as i revved the engine. So the tach seemed to be getting the appropriate power signal to function properly. There are two other wires in the diagram but I can't figure out wha they are and have no idea how to test them. I know just enough about this stuff to get myself into trouble, and not much else! Anyway, if anyone has any experience troubleshooting a dead tach I would be super grateful.

 

If you follow the wiring diagram.... yellow/green is the tach signal from the ECU, green/black is ground, and brown/blue is the 12V feed for the tach and the instrument lights, check the fuse for tail lights or see they are all working. If all OK, then you may have to open up the cluster and see that all circuits are intact to the tach.

 

Ok, I'm going to open it back up today and check. If it is something inside the cluster is that repairable?

 

Any electrical issue - do the drill.

Im concerned about the 3 or 4 volts. That says reg is unhappy - or at least needs checking.

 

The three wires for the thank tested good, I guess the next step is to pull off the instrument cluster. For now I just put it all back together, I'm eager to ride it around.

 

I just got back from my first ride after getting it all back together, the speedometer doesn't function either, I guess I'll be taking apart the gauge cluster this weekend

 

I've read elsewhere around here there may be a trace or ground not making contact, so perhaps broken you have to repair solder it, 'er sumthin. Others with experience may chime in.

 

Ok, so I took off the instrument cluster, found the wires that correspond to the copper strips on the back and did some tests. These were all taken at the back of the circuit board, not at connectors.
First thing that is interesting is that all the bulbs work.
On the Tachometer side:

at the yellow/green wire I get .57 - .60 volts at idle then it increases as I rev the engine up to 2 volts , I didn't rev it too high.
on the brown blue I get 13.8 volts, this one goes to the bulb.

On the speedometer side:

I get 7.24 volts steady at the pink wire
the brown blue wire has 13.8 volts

Between the two I tested resistance and got 1 ohm with the bike running, it dropped to .4 when I shut the bike off.

Everything on the lcd seems to work fine including the trip meter.

So, I'm kind of at a loss - I don't know if those values are correct, and if they are I'm not sure what else there is to check. So if anyone has any insight or can refer me to a someone adept at repairing these types of things within a hundred miles or so of Arlington, VA I would greatly appreciate it.

Thanks!!

 

Ok, I took apart the gauge cluster. The speedo and tach both have circuit boards, on each there was a resistor, (the same one) that looks like it blew. I took it to an electronics repair shop, but they can't do anything without the schematic for the circuit board. The two resistors are definitely toast and I'm imagining I'd have to be very lucky if none of the other parts on the board aren't also fried. I'm looking at used gauges on eBay now, and also wondering if anyone has sent one of these off to get repaired, or even better if someone has the schematic for the circuit board.

Thanks

 

Ok, so the latest development is that I got one quote for $150 per hour labor to fix the tach and speedo not including $25 shipping. If anyone has a clear image of their speedo or tach circuit boards could you please post it? I can't identify the burnt out resistor because it is blackened beyond recognition. My hope is that if I can replace that one resistor then that will solve the problem. It would be a $2 fix instead of $175.

 

So, I ended up just buying a used instrument panel on eBay for $165. So, the electrical failure cost me the following: $99 for ECU, $165 tach and speedo, $80 for a new battery, and $22 for headlight bulbs -all together $366. It all could have been avoided. I could have checked the regulator when I replaced the stator, though I cut myself some slack for that as I didn't own the bike at the time. Then the evening I first got it registered I took it out for about an hour, the next morning it wouldn't start. That's when I should have checked everything out, even so when I had it out that day it it started running weird and if I had just pulled over right away I probably could have avoided frying everything to death. Anyway, moral of the story is if you don't have a beefy misfit rectifier get one right away, it will end up saving you a bunch of money. The one I got was an FHO11aa from a yamaha R1, the connectors are also available from eBay the same ones that fit the later versions of this regulator). The fins on this thing are huge but still fit under the body work, I just had to position it differently than the original and drill a couple of holes for the bolts. I know there is a ton of info on this stuff all over the place, but maybe some of this will be helpful to those that have not upgraded their electrics.