Starting help..please

[DeanR]

So, to follow up on my no start... new battery and I'm good to go, except..

As I was in the process of putting in the new battery, screwdriver touched something it shouldn't. Nice big spark.
Starts right up, but now I have no headlight or speedo/tach lights. Taillight, turn signals, horn all ok. All fuses are ok and I don't know where else to look?

[3Phase]

So, to follow up on my no start... new battery and I'm good to go, except..

As I was in the process of putting in the new battery, screwdriver touched something it shouldn't. Nice big spark.
Starts right up, but now I have no headlight or speedo/tach lights. Taillight, turn signals, horn all ok. All fuses are ok and I don't know where else to look?

For a 1980 Special:

Check the voltage on the Red/Yellow wire at the Headlight fuse in case it popped but still looks good.

Remove the fuel tank and check the voltage on the Red/Yellow wire at the Headlight relay connector. It's not likely because there are no splices or junctions between the fuse and the relay but if there is no voltage at the connector, trace the Red/Yellow wire from the fuse block to the relay.

If the voltage is good then momentarily jumper the White wire to the Red/Yellow wire. The relay should click and latch ON. The lights should come on and stay on until you turn off the ignition switch.

If the relay doesn't work then replace the relay.

If the relay works when momentarily jumpered to 12V then start the engine and check for 12 Volts DC on the White wire to see if the diode in the wiring harness is working.


If none of the above works or you don't want to do all that: unplug the Headlight relay and jumper the Red/Yellow wire to the Blue/Black wire. The lights should come on immediately with the ignition switch and stay on until you turn it off.

If the lights still don't work with the relay bypassed there's a problem with the RLU or the lighting wiring but I have no idea what you could have touched with a screwdriver at the battery that would do that.

.

[DeanR]

Thanks Scott. I'll try to find that headlight relay and see what happens.

[DeanR]

Thanks Scott. I'll try to find that headlight relay and see what happens.

Is this what you're referring to?
This is a shot from the parts bike.

[3Phase]

That's the one!

The relay for the '78/'79 bikes is different and the relays won't interchange without some relatively simple changes but let's not go there and stick to getting your lights working.

Red/Yellow is 12V from the fuse
Blue/Black feeds that 12V to the RLU
White is one of the three stator wires from the alternator. Yamaha extended it and stuck a diode on it for sort-of-12V DC to operate the relay coil
Black is, erm, Ground

There is a latching diode inside the relay too, Blue/Black to White, I think, to keep the relay ON once it's triggered so the relay doesn't chatter at low voltage/low RPM and the lights don't flicker at stoplights. It also keeps the lights on if the engine dies or you use the kill switch.

If I may ask: Where did you touch with the screwdriver and shoot sparks?

.

[DeanR]

That's the one!

If I may ask: Where did you touch with the screwdriver and shoot sparks?

.

I think it was as I was about to connect up the pos termnial of the new battery. Don't know exactly what was touched.

Out to pull the tank.....again.

[DiverRay]

I think it was as I was about to connect up the pos termnial of the new battery. Don't know exactly what was touched.

You ALWAYS connect positive and THEN the Negative on the battery! Now you know why. Ground is ALWAYS FIRST off and LAST on! You may want to check around the starter relay, as you could have melted a wire or connector at the relay, and that would be the problem. Disconnect the ground wire, and pull on all the wires near the starter relay, then use a VOM to check the resistance between the battery cable and connections at the fuse block. IF you have more than 2 Ohms, you have a bad wire/connector.

[DeanR]

If none of the above works or you don't want to do all that: unplug the Headlight relay and jumper the Red/Yellow wire to the Blue/Black wire. The lights should come on immediately with the ignition switch and stay on until you turn it off.

No headlight doing the above.

Ground is ALWAYS FIRST off and LAST on! You may want to check around the starter relay, as you could have melted a wire or connector at the relay, and that would be the problem. Disconnect the ground wire, and pull on all the wires near the starter relay, then use a VOM to check the resistance between the battery cable and connections at the fuse block. IF you have more than 2 Ohms, you have a bad wire/connector.

I know diddly about the electrics Ray. But I do know that. Just had a stupid moment.

Where is the starter relay?

[3Phase]

No headlight doing the above.

Did you check to see if there is any voltage at the Headlight relay on the Red/Yellow wire?

You don't have to get out a meter or do anything complicated, just short it to ground with a screwdriver and see if the fuse blows.

... Where is the starter relay?

The Start relay is under the right-hand cover, next to the Fuse block and below the positive terminal of the battery. The positive battery cable connects to the Start relay.

Starter Relay Yamaha XS360, XS400, XS750, XS850, XS1100
Item condition:New
Quantity: 1 | 10 available
Price:GBP 40.49 | Approximately US $53.14



Honestly, Dean, except for the connection in the Fuse block there is nothing in that area of the bike that has anything to do with the just the headlight and instrument lights and that you could hit with a screwdriver.

.

[DeanR]

Check the voltage on the Red/Yellow wire at the Headlight fuse in case it popped but still looks good.

0.11

Did you check to see if there is any voltage at the Headlight relay on the Red/Yellow wire?

'0'

fusebox readings: fuses are all ok
1 - 0 empty
2 - 12.2 tail light
3 - 0.11 ....... assuming that's the headlight position(my labelling was somehow incorrect)
4 - 11.9 turn sig
5 - 0 empty
6 - 11.85 ignition
battery - 13.08

sorry to be asking basic elec. questions guys, but I need to be told what to do! I barely know how to turn the voltmeter on!

[DiverRay]

OK, the starter relay red/white wire is how you get power to the rest of the system. The blue/white wire is to start the bike.
As you have power to some of the systems, you will need to look at the headlight again. I would start at the headlight itself, and pull the connector so you can measure to see if you have any voltage there WITH THE ENGINE RUNNING. Remember, if you don't start the engine the headlight will not come on. You CAN kill the engine after you start it with the kill switch and the headlight should stay on, so you can do that and then hook up a small charger to keep the power flowing while you check things.
Update in a few minutes...

[DiverRay]

OK, looked at the factory manual.
1. Check the Blue/Black wire at the reserve unit. Should be 12V. If not, Headlight relay or deeper into the wires.
2. Check Blue/Yellow wire at the reserve unit. Should be battery voltage, if not reserve unit is bad.
3. Headlight voltage at Yellow wire/headlight? if no, dimmer switch or wires.
This should be a start, and I can add more if you still can't find the problem. I have a factory manual with the trouble shooting block diagram that helps a LOT.

[DeanR]

OK, looked at the factory manual.
1. Check the Blue/Black wire at the reserve unit. Should be 12V. If not, Headlight relay or deeper into the wires.
2. Check Blue/Yellow wire at the reserve unit. Should be battery voltage, if not reserve unit is bad.
3. Headlight voltage at Yellow wire/headlight? if no, dimmer switch or wires.
This should be a start, and I can add more if you still can't find the problem. I have a factory manual with the trouble shooting block diagram that helps a LOT.

Assuming those RLU readings are checked at the bullet connectors (in the harness connector) for those two wires, as that is where they are exposed? Bike running?



Headlight yellow voltage wire appears to be 0.

Not seeing anything burned looking at the starter relay.

[DiverRay]

Take a 2" bit of fine wire, bell wire works best, and strip about 1/2" on each end. wrap one end around the VOM lead, and push the other end into the connector along the proper color wire. You should be able to get a reading that way. Play with it at first with the bike off, and the VOM on resistance to see how far you will need to insert the wire. This is how you check with everything plugged in, and bike running without causing damage.
I would also do a resistance check from the black wire at the headlight to ground. It should be 0 to 2 Ohms MAX. This wire is joined to others and they all ground on the rear screw of the Reg/Rec mount. you will see about three or 4 wires, mostly brown, there.

[3Phase]

The fuses are NOT all okay, the fuse is bad or the fuse block is FUBAR.

... fusebox readings: fuses are all ok

1 - 0 empty
2 - 12.2 tail light
3 - 0.11 ....... assuming that's the headlight position(my labelling was somehow incorrect)
4 - 11.9 turn sig
5 - 0 empty
6 - 11.85 ignition
battery - 13.08

13V at the battery and 0.11V on the Red/Yellow wire at the Fuse block is not okay. Put the volt meter on both of those tiny little metal test points on the top of the fuse to measure the voltage drop and see if you get about 11 or 12 volts

or

swap the Headlight fuse with a good fuse from another circuit.

.