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Discussion Starter · #1 ·
My friend has an old Suzuki that won't charge the battery. He's got a new alternator, and when he revs the engine the headlight gets brighter. There's three wires from the alternator. One to the headlight, one to regulator, and one to rectifier. The one to rectifier seems to change alternating current into direct for charging the battery. He can't get a new regulator or rectifier, and the two he got from the junkyard didn't help. Can anyone tell me if any old regulator/rectifier from a Honda, Yamaha, or Chevy for that matter, will work?
 

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There are generic aftermarket regulator/rectifiers available for older bikes. However, you should know that older bikes (Suzuki's in particular) are notorious for poor charging systems. Most will not charge the battery at idle (even on a good day), some have to have the engine running over 2500 rpm to get to the point of charging the battery.

Here is a quick test...check voltage at the battery with the bike running at idle and at 3000 rpm. At idle, it may read low but at 3000 rpm it should read 13.5-15.0 volts. Any more or less indicates a problem.

Larry
 

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No Worries said:
There's three wires from the alternator. One to the headlight, one to regulator, and one to rectifier.
If that is the case, something is wired incorrectly. Bikes run on DC voltage...the rectifier's job is to convert AC volts to DC volts through a series of diodes. Usually, three wires from the alternator indicates a three phase charging system and all three should go straight to the rectifier.

The regulator makes sure the amount of voltage supplied to the bike's electrical system does not exceed a specific amount (usually 15v). Typically, the wires from the alternator (stator, generator, whatever term you use) go to the rectifier then to the rest of the system and then the regulator dumps off excess voltage via a separate path to ground.

Unless this is some kind of ancient dual-purpose bike, the above is usually true.

Larry
 

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Discussion Starter · #5 ·
Thanks Larry. His Suzuki has separate rectifier and regulator, and we will look for an aftermarket one that has them together. His manual shows the wire to the headlight switch coming back to the rectifier, but it has an on/off switch for the headlight, if that makes any difference.
 

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What year and model is this thing?

Larry
 

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Discussion Starter · #7 ·
larryg said:
What year and model is this thing?

Larry
It's a 78 GS 1000E. I have a 79 GS 1000E, but mine has a different regulator and rectifier (I replaced the stator years ago). Plus, mine doesn't have an on/off switch for the headlight, it's always on.
 

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No Worries said:
It's a 78 GS 1000E. I have a 79 GS 1000E, but mine has a different regulator and rectifier (I replaced the stator years ago). Plus, mine doesn't have an on/off switch for the headlight, it's always on.
Let me see what I can dig up, what your describing doesn't make sense from what I remember...'course, I am older than those bikes :cry:

Larry
 

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Discussion Starter · #11 ·
Well, we couldn't find a regulator for my friend's 78 GS1000, so we got a rectifier/regulator from a Yamaha that fit in the space. Hooked up the wires to the regulator, but not the rectifier, fired it up and the battery charged at 14 volts. Yeah! But it only started charging the battery after the headlight was turned on. While running, we turned off the headlight, and it still charged the battery. Somehow, the headlight can run on alternating current straight from the alternator. But the wire from the headlight back to the rectifier must start the charging process. The old regulator must have been sending all the juice to ground, but it works great now.
 

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Headlights being a huge draw on current will ususally always turn on charging systems. Just like in a car... when you're jumping a motor that is bigger than yours...you turn on your headlights to engage your charging system. I jumped a 454 v-8 with a Festiva before which is the idea I'm talkin about.
 
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