Triumphrat

10-06-2005, 11:07 AM

Hello all,
I'm the new owner of a '99 Thunderbird Sport, and I'm trying to figure out if I have a problem or not. Well, we all have problems, but specifically bike problems.

When I test rode the bike, it stalled and wouldn't restart...the battery was completely dead. The previous owner said he put in a new battery and everything was normal. When I picked up the bike, we put a volt meter on the battery at idle, and the voltage was 13.5v or 14v. So everything seemed fine.

I haven't had a problem starting the bike again. But I bought a Battery Tender Plus and plugged it in 2 days ago. The red light was on (and not the green one) indicating it was below 80%. So I left it over night and it showed fully charged yesterday. I went out for a ride, about 10 miles, and plugged the charger back in. Again, red light on, green light off. I unplugged the charger and checked the voltage at the battery at idle...12.5v. If I rev it a little, the voltage will go up to about 14v.

It seems to me that even at idle, the alternator should produce at least 13.5 volts. And after riding, I didn't expect a low charge again. It only makes me wonder because the charger was detecting low current.

I'm going to check the alternator and voltage regulator, but should I be concerned?

thanks

jimmyj900 · 10-06-2005, 12:20 PM

The alternator voltage is typically below the battery voltage at low rpms on these bikes and won't charge the battery until someplace around 2500 rpm. That's why Triumph specs the alternator at 14.5V at 5500 rpm.

Your battery voltage should be 13.2V with the ignition off and you'll have a slightly lower voltage at an idle.

Roll up the idle slowly while monitoring the battery voltage and it should increase to 13.5 or more by 3000 rpm.

ALSO, wire brush your battery terminals and cable ends until shiny, coat with hi-temp wheel bearing grease and reassemble!

A dirty/oxidized terminal will cause a resistive voltage drop that increases with current, so the harder the alternator tries to charge (higher voltage) the more the voltage will drop before reaching the battery.

A defective battery with excessive internal resistance will cause the same problem as dirty terminals -- but you can't fix it.

Jim

10-06-2005, 01:15 PM

great, thanks for the info! I've never heard of using wheel bearing grease before. But it sounds like I'm in good shape.

jimmyj900 · 10-06-2005, 10:06 PM

Quote:

I've never heard of using wheel bearing grease before.

The thing about the hi-temp grease is that it stays where you put it. Most other greases will flow when they get warm and melt all over the place, but seem to bake out and harden when you want it to stay soft. Must be one of Murphy's laws or something...

Jim