Low Charging Voltage...

[bmannon]

First post here. Just got my first Max last week. It is a 86. Ive wanted one of these since 85 when they first came out, and finally got one.

Bike runs fine and starts every time, but... lights dim when motor is revved so I checked the voltage at the battery. When it is idling it will be around 12.5-12.8vdc and when I rev it it will drop to ~12vdc. Engine off the battery voltage is about 12.2vdc.

Any ideas whats causing this?

Thanks in advance!!!!

 

[maleko89]

Use this fault finding diagram.
https://www.electrosport.com/electrosport_fault_finding.html

You won't go to 'D', the R/R doesn't have more than four colored wires.

But, Check your stator AC voltage, and test the R/R using the Yami service manual. Check connections of 3 white wires coming from stator and going to R/R. Check and make sure R/R mount is clean, otherwise won't ground properly.

 

[bmannon]

i will print it out and check it later, thank you!

 

[Buster Hymen]

The site Mark posted is a good place to start. I'm trying to figure out why the voltage goes down when you rev it up and your idle voltage is higher than when you rev it. Are you sure you posted that right? One of the biggest problems with voltage loss on a VMax is the connectors in the charging system. You can try cleaning them but most of us cut them out and solder them. Also the ground on your R/R is the chasis of the unit and it grounds itself to the bike frame where it is bolted on. This is usually corroded and a bad ground. You can clean this, or run a ground wire from the battery and put it unger one of the bolts that holds it to the frame.

 

[bmannon]

Yeap i posted it correctly, voltage drops and lites dim when the motor is revved, i suspect a bad ground, but the way my luck runs it is something MUCH more expensive.

Next weekend I am planning on changing the filters, rear tire and checking the electrical system per the flow chart that mark posted. I have already printed it and been studying.

When the r/r or the actual alternator go out dont they just usually quit completly? I think it is a connection problem and keeping my fingers crossed!!!!!!!

The site Mark posted is a good place to start. I'm trying to figure out why the voltage goes down when you rev it up and your idle voltage is higher than when you rev it. Are you sure you posted that right? One of the biggest problems with voltage loss on a VMax is the connectors in the charging system. You can try cleaning them but most of us cut them out and solder them. Also the ground on your R/R is the chasis of the unit and it grounds itself to the bike frame where it is bolted on. This is usually corroded and a bad ground. You can clean this, or run a ground wire from the battery and put it unger one of the bolts that holds it to the frame.

 

[maleko89]

It sounds like your R/R could be failing. The battery should read 13 volts with the engine off. Once running, should never get below 13 volts.

Stators rarely go bad, when they due it's usually because of bad/dirty connector and thus causes heat.

 

[bmannon]

if that turns out to be the problem would this be a good replacement....

It sounds like your R/R could be failing. The battery should read 13 volts with the engine off. Once running, should never get below 13 volts.

Stators rarely go bad, when they due it's usually because of bad/dirty connector and thus causes heat.

 

[maleko89]

No, that's the early model R/R. You want one from 1996 or later, it has a separate ground wire and heat fins. Best bet would be to order one from Mike Barth at University Motors in Fargo. Tell him you're a member of the V-max list and you'll get 15% over dealer cost.

 

[bmannon]

thanks for the info, i will test everything next week and report back!

No, that's the early model R/R. You want one from 1996 or later, it has a separate ground wire and heat fins. Best bet would be to order one from Mike Barth at University Motors in Fargo. Tell him you're a member of the V-max list and you'll get 15% over dealer cost.

 

[Buster Hymen]

I have a hunch it is not your R/R but just your connections. If you either clean them up really good or eliminate them, you can easily pick up 1 volt more at the battery.

 

[bmannon]

thats what i am hoping for....

I have a hunch it is not your R/R but just your connections. If you either clean them up really good or eliminate them, you can easily pick up 1 volt more at the battery.

 

[davidon]

OK related problem. Battery fully charged before riding. Ride for about an hour come back and stop engine. Try to start and barely turns over. Voltage is at 11.75. Checked Stator before this and was fine, Checked R/R before riding..diode test fine... Output about 13.9V when reving. Connections looks fine. Have HD ground kit. If the battery does not hold charge will a charger not help? After charging, battery back up to about 12.8V. Is this a sign of a bad battery (pc680 by the way)

D

 

[bmannon]

if the bike is putting out 13.9 volts and the battery wont stay charged then i would assume a defective battery.

whats weird is mine is putting out low voltage and it starts every time, yours is putting out specified voltage and wont start, weird!

 

[jfeagins]

If the battery is fully charged and everything's fine for an hour's ride, then you shut it off and immediately it won't restart, you may have the same problem with the starter that I experienced.

You might try removing the starter and cleaning it out and re-lubing the needle bearings. You can get a complete rebuild kit for around $50.00 - $60.00 and have new brushes to install while you have it off.

With mine, the brushes looked fine, but on one end (I forget front or rear) of the starter you will find needle bearings that are probably dried out and gunked up with brush dust. Clean those and relube them with hi-heat grease. The other end has a sealed bearing and is probably fine.

This little maintenence made all the difference in the world with the hot-starting issue for my 85 max.

Good luck.

 

[Buster Hymen]

If the battery is fully charged and everything's fine for an hour's ride, then you shut it off and immediately it won't restart, you may have the same problem with the starter that I experienced.

You might try removing the starter and cleaning it out and re-lubing the needle bearings. You can get a complete rebuild kit for around $50.00 - $60.00 and have new brushes to install while you have it off.

With mine, the brushes looked fine, but on one end (I forget front or rear) of the starter you will find needle bearings that are probably dried out and gunked up with brush dust. Clean those and relube them with hi-heat grease. The other end has a sealed bearing and is probably fine.

This little maintenence made all the difference in the world with the hot-starting issue for my 85 max.

Good luck.

You bring up a good point. What might seem like a charging or battery issue can be a starter or starter clutch issue.

 

[maleko89]

That may be a problem...but he originally said batter was 12.2 when returning from a ride. That definitely is a problem.

 

[bmannon]

Thanks for all the info everyone provided, my charging problem is now fixed. Here is what I did....

I cut out the connector between the alternator and r/r and soldered/heat shrinked the connections.

Ran the red wire from the r/r thru an inline fuse then directly to the (+) of the battey.

Ran a 12 gauge ground wire from one of the mounting screws on the r/r to the (-) of the battery.

It took a few hours to do but the results were well worth it. I am now getting just a little better than 14 vdc at my battery terminals :eusa_dance:

 

[Buster Hymen]

Thanks for all the info everyone provided, my charging problem is now fixed. Here is what I did....

I cut out the connector between the alternator and r/r and soldered/heat shrinked the connections.

Ran the red wire from the r/r thru an inline fuse then directly to the (+) of the battey.

Ran a 12 gauge ground wire from one of the mounting screws on the r/r to the (-) of the battery.

It took a few hours to do but the results were well worth it. I am now getting just a little better than 14 vdc at my battery terminals :eusa_dance:

Sweet! :thumbup1: It's amazing the voltage you loose through the connectors. Main thing is that you fixed it and it was a cheap $ fix.

 

[randyreber2]

First post here. Just got my first Max last week. It is a 86. Ive wanted one of these since 85 when they first came out, and finally got one.

Bike runs fine and starts every time, but... lights dim when motor is revved so I checked the voltage at the battery. When it is idling it will be around 12.5-12.8vdc and when I rev it it will drop to ~12vdc. Engine off the battery voltage is about 12.2vdc.

Any ideas whats causing this?

Thanks in advance!!!!

I had the same problem and it was the plug on the 30 amp fuses. They were corroded so I cleaned the plug and now it shows 14 volts at 1000 rpm