XJ650J Tach and Dash Lights Not Working

I removed the instrument cluster before winter and cleaned it up and lubed the speedo over winter.

The good news is that with a new speedo cable and a cleaned an lubed speedo clutch, the speedo now is as smooth as butter.

The bad news is that my tachometer and the "dash" lights are no longer working. All other lights work just fine. Bike runs just fine. Brake lights, turn signals, horn, warning lights, all fine. Just the two bulbs that light up behind the speedo and tach and the tach itself not working.

The fact that the cluster was fine last fall, I had the cluster out over the winter and now there is a problem means that there is a really good chance that I messed something up.

I'm not sure if I'm dealing with one problem or two.

Here's what I've looked at so far:

• Any wires I forgot to plug in in the headlight bucket? Nope, all the non-used connectors seem to match the wiring diagram.
• Fuses? They all checked out.
• Bulbs? They all check out fine
• Headlight relay? Tried a different one with no difference (this may have been grasping at straws)
• TCI not sending signal to tach? Maybe, but TCI works well enough so that it runs fine

Would there be a poor ground somewhere that could effect the tach and dash lights but nothing else?

What's my next move?

Thanks

 

dash lights try changing the bulbs.
it is a simple circuit

 

Most likely since the non functioning tach uses a different 12V source than the indicator bulbs but shares the ground

It is easy to prove, just go inside the headlight bucket and find the tach 4 pin connector and the speedo 3 pin connector. Check the black wires for continuity to the frame - they should be shorted

High beam indicator and auto cancel working?

 

High beam indicator - tested, NOT working. Should have tested that before.

T/S auto cancel: tested, appears to NOT be working. I drove around like a bonehead with a turn signal flashing for a while and it never stopped.

Looking at the schematic, it looks like they share the black ground, so that's a good bit of data. But other things seem to share the black ground that are working (flashers and tail light), which confuses me.

Do I assume there is a continuity problem with the black ground somewhere and start doing continuity checks at all the endpoints where the black wire goes?

 

all the grounds are black in the wiring diagram it just shows everything going to the same wire for ground .
it is likely that the ground wire in the connector is not making good contact to the mating connector

test ground from bulb socket as it is the end of the line if bad cheak from connector to main harness. then check from tach connector to bulb socket

 

I didn’t see it mentioned, is the headlight working? If so it almost has to be some ground connection as that is needed for the lights and the reed switch for the canceling unit. All located in the cluster.

Did you check the ground at the harness like @Rooster53 asked? Definitely next step there. Just because the blinkers and tail light work does not mean the cluster is grounded, same wire in circuit but doesn’t mean there is continuity from the harness main ground connection to all the other connection points.

 

Headlight high and low beam works.

I checked and cleaned up ground points at the coils and right under the rectifier.

Continuity of the black ground wire doesn't seem to be the problem - I can put 12V just about anywhere on the frame and read 12V at those ground wires in the bucket, which tells me the black wire in the bucket is grounded to the frame.

To add insult to injury, I somehow managed to wreck the TCI as well. Only runs on 1 and 4 now. I swapped over the TCI from a 750 for a second and it ran fine, so really seems like TCI is cooked now.

 

Huh? What do you mean you can put 12V on the frame? An open ground wire is going to measure battery voltage if you reference it to ground (the frame).

Go back to checking continuity at those black wires for the circuits that are not working, like stated before they should ohm a short to ground.

Every one of those dots you see on the schematic is not exactly how it is built, but it does represent a splice point either at a crimp or at wires doubled up in a connector. It is not hard to imagine how an open in one of those could cause your issue.

 

To test the continuity of the black (ground) to frame, I made a simple circuit using a battery:
Battery -> frame -> ground wire in bucket -> DMM -> back to battery.
That circuit tells me the black ground wire in the bucket has continuity to ground.

 

So did the tach work then?

OK, but I thought that was what the battery in the DMM was for

So maybe you do have a 12V problem, kind of depends on if the tach worked with the other TCI

If so, go to voltage mode and just check the power at the respective connectors - got 12V, got ground, must me a bad bulb or bad meter harness

Start the bike up and stall it with the sidestand so the headlight relay will stay energized to check the 12V, or bypass the headlight relay to get the 12V, or energize the headlight relay by momentarily applying 12V to the appropriate AC Generator pin

....but headlight works and that voltage is used to power the headlight indicator bulb - so back to missing ground, bad bulb???

 

This is absolutely correct, and there is more than one "harness ground" on the bike. The one at the rear coil mounting bolt is one, there is another one by the regulator/TCI mounting, and on some bikes a third "harness ground wire to frame" mounting point.

How did u fry the TCI?

 

No. Still no worky. Maybe the tach is bad???

Either my el cheapo DMM doesn't do that or I don't know how to use it. Most likely the latter.

Where would this be? I've only found the one on the coil mount and one under the rectifier so far - and not counting the engine to battery wire.

Not sure. My best guess is that maybe I started the bike with a ground disconnected??

 

1 or 2 grounds at ignition coils.

there is a ground from motor to frame left side if i remember correctly

 

That bike only has one ground for the harness from the factory.

Tach not working is another indicator of a missing ground to the gauges and lights.

Have you checked ground at the actual connections in the bucket for the cluster?

 

Yes, I think so. I made this simple circuit:
Battery -> frame -> ground wire(s) in bucket -> DMM -> back to battery.
And it read 12V.
Which to me indicates that I have continuity from the ground wires in the bucket to the frame.

 

Right at the three connections for the cluster? Not just the grounds in the bucket.

 

Correct, putting the probe on the pin for the black wires in the connectors.

 

Tough one man, if the grounds are good for all three connectors I can't really see how you would have 12V+ issues on all three harnesses as well. The lighting circuit is really simple, 12 volts into the connectors and the wires go right to bulb holders. Did you try and tow a truck with the wiring harnesses for the cluster?

I would get my meter out again and check for 12V (positive and ground) on the harness (from bike) pins and see if you're getting power for the lighting, tach, and high beam individually.

 

Ya, I guess I'm just going to have to get in there and get a "running" voltage on each set of pins and see what we have.

Does anybody know what the readings on the tach wires (orange and brown) should look like? Does that voltage vary with RPM?

And now, just for a double kick in the @$$, I'm in quarantine with the covids. So it may be a few days before I can get out and do some more testing.

 

there is one wire running from 1 ignition coil to the tach tack counts the pulses of that wire and converts to rpm
orange and brown wires will have 12 volts as the tci fires only 1 of these wires is connected to the tach.

 

Got back out to do some testing today.

Also now, just because screw me, the headlight isn't working.

Getting no voltage at the following:
Dash lights
Tach
Hi beam indicator
and now headlight

Just for grins, I tried swapping the diode block. No change.

I'm almost ready to start removing the harness so that I can inspect every wire, inch by inch. Maybe my wife hired some rodent to chew on the wires in order to sabotage the bike or something. Anybody got a better idea?

Also, what is the tape called that you are supposed to use to repair/create wiring harnesses?

 

Wire Harness Tape:
Factory wire harness bundles were taped with a black electrically-insulating protective VINYL ELECTRICAL TAPE WRAP to provide both an orderly routing of the main harness wires and for additional wire protection. We have the correct 19mm wide black, high-voltage, adhesive-backed, all-weather stretch tape to allow you to repair or re-tape your harness. NOTE: XJ750 Maxim models that used this hard-shell, plastic ribbed tubing to protect the wire bundles had the hard-shell tubing externally wrapped with this tape.

 

You could do that, but it might be better to know what you are looking for just in case there is not an obvious break somewhere

So dash lights, high beam indicator, and and headlight power is from the headlight relay.

That's not specific enough to really help out. We would need to know specific points for no voltage.

Try the tach:

With the key switched to on at the 4 pin connector do you have 12V at the Br wire in repsect to chassis ground?
No - look for open signal fuse line
Yes
Do you have 12V at the Br wire in respect to the B wire on the 4 pin connector?
No - look for open ground wire in main harness
Yes
Tach is defective or missing iginition signal - verify ignition signal

Dash lights, hi beam indicator, headlight - activate headlight cirucuit as directed in post #10

Do you have 12V at either the Y or G wire on the headlight H4 connector in repect to chassis ground?
No - troubeshoot headlight relay circuit malfunction or open wire / switch
Yes
Do you have 12V at either the Y or G wire on the headlight H4 connector in respect to the B wire on the H4 connector?
No - look for open ground wire in main harness
Yes headlight should be illuminated, verify bulb

 

yamaha runs a ground wire then crimps on feeder grounds.

they do the same thing for the brown power wire from the key to split off for the fuse box

 

Update: I spent some time combing over the harness. Checking and double checking every connection, and looking for any signs of damage. I had the harness out of the bucket and pretty much ready to remove. Then I hooked up everything again (outside the bucket). No change. Then I re-checked everything AGAIN and found the headlight circuit fuse blown. Replaced that fuse and all the sudden got my headlight, dash lights and high beam indicator back.

The tach still didn't work, and the TCI was still toast (only firing on 1&4).

Got out the DMM again, and now I'm getting voltage to the tach - that's a lot better. Swapped out a known good TCI and still no tach.

I'm now assuming that tach is bad - maybe I blew it up by miswiring something, maybe it got messed up when out of the bike over the winter. Who knows?

I'm also 99% sure that the TCI is bad, since I can swap it out and it will run on all 4. Also, the "good" TCI doesn't make the tach work either.

I have a "new" tach on the way, still looking for a replacement TCI.

What happened? Not sure. A few possibilities that I can think of:
1. The fuse was sketchy all along, and my tinkering managed to fry the tach and TCI. I could have sworn I swapped out that fuse on day 1, but maybe not.
2. When putting the thing back together this spring, I connected something incorrectly, which caused the tach to fry and some lights not to work, and then later I fried the TCI by trying to run it without a ground connected. Somehow then managed to blow the fuse while testing (not surprising, could have easily shorted something out and blown it). Carefully reconnecting and replacing the fuse results in a "fix" of most symptoms, except for tach and TCI.
3. There was and still is a fault lurking inside the harness somewhere, and just jiggling and moving the harness "fixed" it for now.

My money is on #2.

I've got some work to do while I wait for the tach to show up - I've got a rebuilt caliper and master cylinder to swap out, along with all new brake lines. My 1&4 coil also reads 0 Ohm on the secondary side, so I'll replace that (although it obviously still works).

 

the tach works off of the spark on 1 of the ignition coils if you are not getting spark on cylinder 2 and 3 the tach is not going to be picking up the signal from that coil pack as it is not firing 2 and 3

 

I had hoped that the tach would start working when I swapped to the TCI that actually fired 2/3. But no luck.

 

OK, still don't know exactly what happened with the lights, but had a huge facepalm moment today.

Tach was wired incorrectly. When I took it apart I marked where the black and brown wires went, but I marked them wrong. So when I put it back together, I put it back correctly as far as my markings were concerned. But that was incorrect.

For future me or anyone else, here is the correct wiring of the tach: