Oil light led

[norton1974_imp]

Is there a repair option for replacing low pressure light led in the tach?
Light never worked and switch checks good.
Have not checked wire , that is next on list
Thanks,for your time
GR

 

[pekingduck]

Funny you should ask, was just working on a set of instruments today.

Unplug the white 6-pin connector inside the headlight case, and, on the harness side, check for a ground on the blue wire with the red tracer. The switch is normally closed, and provides the ground to the indicator. The power to the light is on the circuit board that feeds the rest of the instruments.

If you need to take the instruments apart to check wiring, unbolt the whole assembly's 2 bolts under the top clamp, and lay it all on a big towel on the dining room table. There are about 25 screws to get to the last part of the wiring that plugs into the circuit board.



The LED is on the inside of the circuit board of the tach itself, held on by one screw, but you would have to pull the tach needle off to access it, and unsolder the LED. No spec on the LED values, or diagram of the printed circuits are available. Hopefully the problem is a poor or open connection somewhere.

If it's deemed not easily repairable, I'd drill a hole in the center steering nut for a nice big red LED, run one wire to any switched-on power, and the ground to the oil pressure switch. The early Japan market CB750s had a nice big red light as a speed warning.

 

[norton1974_imp]

Hello,thank you for your reply.Funny you should ask, was just working on a set of instruments today.

Unplug the white 6-pin connector inside the headlight case, and, on the harness side, check for a ground on the blue wire with the red tracer. The switch is normally closed, and provides the ground to the indicator. The power to the light is on the circuit board that feeds the rest of the instruments.

If you need to take the instruments apart to check wiring, unbolt the whole assembly's 2 bolts under the top clamp, and lay it all on a big towel on the dining room table. There are about 25 screws to get to the last part of the wiring that plugs into the circuit board.




[/QUOTE]
Thank you,great idea useing steam.
Will check wire in h/l bucket first
Thanks and cheers

Any ship can be a mine sweeper.
Once

 

[norton1974_imp]

Hello, the oil pressure wire checks out from switch to plug.
what supplies the power for light ?
White connector shows 6wire white plug.
However only 5 wires are used.
One is blocked with a plug
Wireing diagram shows green ground wire
That is not present.
Any thoughts?
Thanks for your time
Gr

 

[pekingduck]

Hello, the oil pressure wire checks out from switch to plug.
what supplies the power for light ?
White connector shows 6wire white plug.
However only 5 wires are used.
One is blocked with a plug
Wireing diagram shows green ground wire
That is not present.
Any thoughts?
Thanks for your time
Gr

White 6-pin connector only uses 5 of the pins. Green ground wire goes to the gray 8-pin connector, so not likely a problem. There is a sub-harness that the 3 plugs in the headlight lead to, but you will have to take the meter off the bike and put it onto a table to work with. Then you can test continuity on the dark-blue/red wire trough this sub-harness. if it's good, plug the white sub-harness connector into the connector in the headlight, and check that wire to ground. If it's got continuity, then it looks like the LED may be bad, which is very rare.

 

[norton1974_imp]

Hello.
thank you for your help.
this clears a lot .
bike has 9500 miles on it and
i find it hard that led is blown.
this project should kill an afternoon.
Tally Ho
Gr

 

[pekingduck]

Hello.
thank you for your help.
this clears a lot .
bike has 9500 miles on it and
i find it hard that led is blown.
this project should kill an afternoon.
Tally Ho
Gr

Good luck. Let us know how it goes.

 

[norton1974_imp]

Hello, as I have only had this bike for a few months, I am not familiar with the wiring on it.
Do I need to remove the fuel tank to get with the plugs on the other side of the wires?
I have the Honda shop manual , and that is not covered.
Any advice would be greatly appreciated.
Thank you in advance.
GR.

 

[pekingduck]

Hello, as I have only had this bike for a few months, I am not familiar with the wiring on it.
Do I need to remove the fuel tank to get with the plugs on the other side of the wires?
I have the Honda shop manual , and that is not covered.
Any advice would be greatly appreciated.
Thank you in advance.
GR.

No need to take off tank. the 3 connectors from the meter all go into the back of the headlight case and plug in there.

 

[norton1974_imp]

Funny you should ask, was just working on a set of instruments today.

Unplug the white 6-pin connector inside the headlight case, and, on the harness side, check for a ground on the blue wire with the red tracer. The switch is normally closed, and provides the ground to the indicator. The power to the light is on the circuit board that feeds the rest of the instruments.

If you need to take the instruments apart to check wiring, unbolt the whole assembly's 2 bolts under the top clamp, and lay it all on a big towel on the dining room table. There are about 25 screws to get to the last part of the wiring that plugs into the circuit board.



The LED is on the inside of the circuit board of the tach itself, held on by one screw, but you would have to pull the tach needle off to access it, and unsolder the LED. No spec on the LED values, or diagram of the printed circuits are available. Hopefully the problem is a poor or open connection somewhere.

If it's deemed not easily repairable, I'd drill a hole in the center steering nut for a nice big red LED, run one wire to any switched-on power, and the ground to the oil pressure switch. The early Japan market CB750s had a nice big red light as a speed warning.

Hello,is the oil light power a different source than the light for the tach?
Blue wire with red ground good up to the gauge.

 

[pekingduck]

GR, want to verify a few things.
The light we're talking about is in the tach, not the speedo.
The 10A meter illumination sub-fuse (fuse F) is good.
The switch is on the right side of the engine, at the bottom front of the clutch cover. When the blue/red wire from the switch is grounded, the light does not go on.
There is continuity from the blue/red wire from the switch into the meter.

At this point, the shop manual says the meter assembly should be replaced. (HAH!)
You would have to take the tachometer apart to access the LED, which I don't recommend.
Putting an external light on is the next best option. Just hook a test light to power and to the switch to verify the switch is closing

(BTW, in 1974 I bought my 3rd Norton, a '71 750 Fastback, enjoyed it for 33 years and really regret selling it.)