YUASA YTX15L-BS AGM 12V - PROBLEMS

[MartyNZ]

Tomek, there could more than one fault which causes the charging voltage to be low.

1. AC voltage from alternator low, as Chuck says. See attached page from the workshop manual for AC voltage table at three different engine speeds.

2. Burned connectors in the yellow wires from alternator to regulator. See attached picture.  

3. Poor grounding / earthing at the regulator, the timing case, battery connection, or the rear of the gearbox.  

4. Melted 30 amp fuse. Moving wires to a better fuse holder fixes this. See attached picture. 

WMV11_Alternator&Reg.pdf

 

[Kiwi_Roy]

There are several things that will stop the battery charging as others have mentioned but since the tach is playing up I suspect the headlight is also playing up, have someone ride ahead and watch your light in his mirror.
The headlight relay supplies the tachometer and the regulator Voltage reference.
Relay 1 and relay 2 are in the headlight circuit. The Start relay (#1) must be a 5 pin.


Sent from my shoe phone!

[TomekSZ]

There are several things that will stop the battery charging as others have mentioned but since the tach is playing up I suspect the headlight is also playing up, have someone ride ahead and watch your light in his mirror.

The headlight relay supplies the tachometer and the regulator Voltage reference.

Relay 1 and relay 2 are in the headlight circuit. The Start relay (#1) must be a 5 pin.

 

 

Sent from my shoe phone!

All the relays i repleace for omron 5 pin - not charging again. It is caple, voltage regulator or alternator. Or all the things in the same time

[swooshdave]

 

There are several things that will stop the battery charging as others have mentioned but since the tach is playing up I suspect the headlight is also playing up, have someone ride ahead and watch your light in his mirror.

The headlight relay supplies the tachometer and the regulator Voltage reference.

Relay 1 and relay 2 are in the headlight circuit. The Start relay (#1) must be a 5 pin.

 

 

Sent from my shoe phone!

All the relays i repleace for omron 5 pin - not charging again. It is caple, voltage regulator or alternator. Or all the things in the same time

 

 

Did you check the wiring as suggested before? Especially the grounds?

[GuzziMoto]

If the relays base, where they plug in to the wiring harness, is loose or corroded even a good relay will cause you problems. As Roy said, if you are having charging issues AND tach issues it is probably relay related. As he said, the headlight will also be affected (although not that small running light so if you have that light you may think your headlight is just getting dimmer).

[Kiwi_Roy]

This is a very simple sketch of the charging system but it will serve to point out a few details.

The alternator windings are connected across the two yellow wires. power flows from the wire that happens to be positive (lets say the left side at the moment) through the left side diode out the red wire and through the 30 Amp fuse to the battery. From the battery negative the current returns through the chassis to the regulator case, to the right side Silicon Controlled Rectifier and out the other yellow wire back to the alternator. I should point out that the current can only pass through the SCR if it is turned on by the regulator circuit (battery Voltage is less than 14.6)

 

A split second later the current reverses direction and flows out the right diode, through the battery and back to the alternator through the left SCR

At 5,000 revs per minute it's changing direction 1,166 times per second, it's quite busy.

 

The most important part of the regulator is the regulator circuit, it measures the battery Voltage and decides if it needs to turn on the SCRs and charge the battery, It uses the 12 Volts at the black wire (Voltage Reference) to fire the SCRs if the battery Voltage is a bit low, This wire is tapped into the Red/Black headlight circuit downstream of the headlight relay half way along the tank on the right hand side. You will find a double pin plug with 1 black 1 white wire, just ease the connector apart a little and measure the Voltage on the black.

 

 

I have found several regulators where one internal diode has become disconnected, the sketch shows testing the diodes using a multimeter with diode test feature. If you dont have a diode tester a battery and lamp (not an LED) will do, the lamp should glow at just over half intensity and not at all if you reverse the polarity.

 

Another separate part of the regulator is the charge light, it's pretty useless really, if there's no power on the black wire, the bikes not charging and the light doesn't work. If the headlights not working the first you will know is when the motor conks out.

 

 

 

m   It's very important to have a good ground on the regulator so the current can get back from chassis to the alternator. the factory provided a wire but it has too much resistance because it goes all the way back to the battery, a short No 12 from the regulator case to a timing cover bolt is much better.

Check the 30 Amp fuse and also the connectors in the yellow wires for any sign of discolouration, there should be none.

BTW the resistance between the yellows is very low(1 Ohm or less) and you should be able to measure 50 to 90 Volts AC between them while the bike is running.

 

I have the complete circuit for those that like to study electronic diagrams.