Resistor type speedo/tacho

[vladr]

Does anybody know what is the resisto value/type of the R1 resistor from the dashboard (speedo and tacho).

 

After the classic rectifier issue it burned my computer and also the speedo and tachometer.

 

Dissasmable the dashboard and saw that one of the trasnsisots is totally burned for both clocks.

 

The color it's full black( not sure if it had a colour and burned to the point it's hard to distinguish a color). There are 3 more resistors with different values and code colors but none seem to be the same as the burned one.

 

Decide to solder from 1k and going down to 800, 600 etc. None worked.

 

From my basic knowledge in electronics, on a PCB a back resistor it's a 0 one (a simple bridge without resistance) but looks as a resistor due to the materials used to not dissipate the heat and change the resistance.

 

 

[Grum]

Sounds like you have had a nasty R/R Over Voltage situation. When you say "burned my computer " do you mean the LCD instrument display Or the ECM engine control module?

 

Can you post any pictures of the inside of the speedo and tacho.

 

Attached is a picture of the speedo, note that the resistor visible next to the large black capacitor is a 30ohm 1watt carbon film resistor.

Sorry have never had the instruments apart and there doesn't seem to be any internal wiring info out there.

 

[vladr]

Many thanks Grum for your feedback.Yeah it burned tot he ground the ECM.

 

Bought the motorcycle and the previous owner forgot to tell me regarding this issue, it had a 18v charge on the voltmeter he installed.

 

Me and me dad started to think it s not normal but we though it just "charges the battery faster". Silly us.

 

200 km later a, battery exploded and smoke started to get off the ECM.

 

After many many many hours investigating this topic and making various tests, the ECM was burned and had the br/bl wire grounded.

 

It seems that s pretty normal for the current to flow on the two extremities of the circuit, one was the ECM and the other one the dashboard.

 

Redid all the harness by hand and installed a MOSFET RR bypassing the harness and connected directly to the battery though a 20amp fuse. To be sure I will not get again stranded.

 

RRegarding the speedo, I've measured those ones and indeed most of them are 300ohm. I supposed the same will be this "R1" resistor but it's seems that it's the first one that gets to the speedo, this by logic, should be giving a higher resistance and then the current flow to the 300 ohm ones.

 

And indeed, there was only one topic here with a guy having exactly the same symptoms and asking the same. 

 

BEst bet would be to buy a SH dashboard and that's it, but I was very curious regarding the resistor as Ive also tried to measure the resistance if the burned ones and showed different values, 1000 700 and then started to go down around 350. So not sure if those are the symptoms of a burned resistor 

[Grum]

4 hours ago, vladr said:

After many many many hours investigating this topic and making various tests, the ECM was burned and had the br/bl wire grounded.

 

Sounds like a real mess!!!

The Brown/Black wire you mention is the Ground control wire for the Fuel Cut Relay. I'm sure (but not 100%) that this wire is Grounded by the ECM in the default or unpowered state and remains Grounded until the Fuel Prime time is completed at switch On, then, as you crank the engine and the ECM detects pulses from the Ignition Pulse Generator it will again provide a Ground for the Brown/Black wire to energise the Fuel Cut Relay running the Fuel Pump. 

[vladr]

FOR FUTURE REFERENCE

 

Amazing news, I've bought a SH dashboard and just for curiosity measured the R1 resistance.

 

Strangely, it's a 30 Ohm. Hope this helps for others that pass through the same issue. Soldering one should be the cheapest way to have a working dashboard again.

 

 

Regarding your question Grum, I agree with you but my main issue was that the br/bl wire had an abnormal ground that somehow sent it over the w/bl, br/bu and r/bl wires though the fuse box C from the diagram scheme.

 

 

I've discovered this with a multimeter and checking the fuses with the ground. From all 6 fuses (excluding the clock one) 3 of them had w ground.

 

If I ve unplugged the fuse C, the other 2 D and G (or F don't remember for sure) worked fine without a ground on them.

 

Thus, unplugged all the fuses and checked directly the wires that go from them. And the culipt one was the br/bl.

 

 

The chronological order for he issue was:

 

 

While riding with 18v, dashboard showed 0 and after 10 second engine died.

 

Battery exploded and smoke was coming from the ECM

 

Saw the Maine fuse A blowed so I was thinking this should be an easy fix.

 

Started to blow everytime Ive turned the ignition on. 

 

While testing this and burned over 10 fuses, the ECM started to smoke with the ingition on from the Black wire, this is the point from which something changed in the circuit and the issue with the 3 fuses connected in series started to appear.

 

I assume that the ECM had a ground in the black wire and from then goes to the relay fuel pump and ground the br/bl ones and the respective one ground the other 2 fuses until half of the circuit it's grounded.

 

This explains why the fuel pump was not priming and why the fuse blows.

 

In either way, this issue seems to be solved as it was a 30ohm one. 

 

The bogging one I still think it's something relatively normal as this happens only when the engine is cold, no test to deduct a theory should be performed on a cold engine.

 

I will further test for the over 6RPM issue, that one really has the possibilty to truly be an issue.

 

Many many thanks again Grum for everything, we need more people like you!