over charging! do i need a regulator?

[Guest]

Hello. I have just bought a 1980 gs550 cheap because the wiring between the starter relay and the fuse board had melted due to a short it looked like. I rewired it all and it ran fine. One day it wouldn't start. I pulled the newish battery out and it had boiled dry. I topped it up with acid and started the bike and put a voltmeter across the battery terminals and got 16.2v at 2000 revs. Seems too high. I have bought a second hand original rectifier off ebay the one on the bike is after market. Now my question is do I need to buy a regulator? The rectifier i got was listed as a regulator/rectifier on ebay. But in the haynes manual the regulator and the rectifier are 2 different components. There is no regulator on the bike just a rectifier. But the wiring has been messed about with a lot before I got it. This is probably a stupid question but I am pretty useless at electrics and would appreciate any help! Thanks...

[Steve]

You may have killed the battery if you truly added acid. The only thing that you should add after the initial dose of acid (if the battery is shipped DRY), is distilled water. If you added acid, the battery now has the wrong concentration in it to work properly.

Do you need a regulator? You probably already have one. The early bikes ('79 and older) had separate units, but your '80 should have a combination unit. How many and what color wires are there going to the unit that you just got?

As to the overcharging, check the ground wire coming out of the current R/R (rectifier/regulator) before changing anything. If the ground wire is not making a GOOD connection to a good chassis ground (the battery - terminal is even better), it can show high voltage.

There is also a possibility that the current R/R unit has a "sense" wire that is disconnected. How many and what color wires go to it?

.

[Davy]

Thanks Steve, the current unit has 3 yellows, a red and a black. The black is going to the negative battery terminal and making a good connection. The unit i just bought has a black, a white/red, a white/blue, a red and a yellow. Do you think I should just swap the units and test with a volt meter again? Your help is much appreciated!

[Steve]

It is possible that you have a faulty R/R. Go ahead and subtitute, let us know what you find.

If the stator is original, it will have yellow, white/red and white/blue wires. Connect those wires directly to the R/R wires, color-matching is optional. Note that the white/red stator wire will not have a direct match, in the stock configuration, it disappears into the harness and returns as a white/green wire. Avoid that useless loop, connect all three stator wires directly to the three R/R wires.

.

[Davy]

New regulator, same problem. I suppose its just a case of looking at the wiring diagram and tracing all the wires to see if its been wired up wrong?

[koolaid_kid]

Check your ground wire. It should be a clean, solid connection to the frame, eventually ending up at the negative terminal of the battery.

[Steve]

New regulator, same problem. I suppose its just a case of looking at the wiring diagram and tracing all the wires to see if its been wired up wrong?

It's hard to wire it wrong.

Three wires directly from the stator to the R/R. Color-matching is strictly optional.
Black R/R wire directly to ground, preferably directly to the battery.
Red R/R wire to the red wire in the harness.

Note that on many bikes, the R/R is 'grounded' to its mount, which is usually the battery box. The battery box, though, is rubber-mounted, which means that you MUST have a good wire going to the chassis or the battery - terminal. The battery box does need to be grounded, though, because the starter solenoid is mounted to it. However, the requirements for that ground wire are not nearly as great as the reuirements for the R/R ground, which needs to handle a LOT more current.

If the red wire is not making good connection to the harness you will have charging problems, but it will be undercharged, not over.

.

[Davy]

OK thanks for the advice. The red and black wires go direct to the battery, the wiring has been messed about with a lot. It looks like someone experienced has started to rewire it and then an amateur has finished it off. So now I have checked the ground wire connections to the frame, they are bad and I will renew them. Could this be the cause? Also I will check the black wire from r/r to battery for breaks.
Thanks again!

[koolaid_kid]

OK thanks for the advice. The red and black wires go direct to the battery, the wiring has been messed about with a lot. It looks like someone experienced has started to rewire it and then an amateur has finished it off. So now I have checked the ground wire connections to the frame, they are bad and I will renew them. Could this be the cause?
Thanks again!

Absolutely. A bad ground gives the regulator the impression that not enough voltage is being supplied, so it will try to compensate by increasing voltage.
Fix that and your issues will most likely go away.

[Davy]

Well I have renewed the ground wires to the frame with good connections and it has definately helped, the engine is running nicely now, it was lumpy before, but I am still getting 15.8v at 2000 revs. Do you think the battery may be faulty from when I cooked it before?

[lemonshindig]

A bad battery should not cause a high voltage reading.

Is your headlight on? It should be always on.

-Matt

[koolaid_kid]

No, the regulator part of your regulator/rectfier should keep it closer to 14.5V no matter what. Since you fixed the ground wire, the regulator is the only other thing that could be at fault.

[chef1366]

Check your meter.

[Davy]

Hello again. I suppose it could be a faulty r/r, but seems unlikely I have got a new one thats faulty though certainly possible. Running with the lights on the voltage dropped right down across the battery but the engine ran lumpy again.
On my wiring diagram the red wire from r/r runs through a 15A fuse before going to battery, on the bike it goes straight to battery, is it worth putting a fuse in? The back of the r/r is not a good contact with the frame, although the black wire from r/r is in good contact with frame, could this effect it? Your thoughts are greatly appreciated, thanks.

[koolaid_kid]

You should have a ground wire on one of the bolts holding the R/R to the frame. It should run to the main frame ground point.
If you are running the red wire straight to the battery you should have an in-line fuse there. 15A is acceptable; I use a 20A in case there is a slight surge.