WHY DOES BATTERY KEEP DRAINING ON SUZUKI T500 ?

[ericsattic]

Greetings board members. Here are the symptoms of my problem. Batteries slowly drain down until they are dead. I do not drive the motorcycle much but its started every couple of weeks and I drive two or three miles. Battery would probably drain faster if I drove it more. Battery drains more quickly if the lights and signal lights are used. If the bike is running with the lights or blinkers on and battery goes dead, the bike stops running. But when the lights and blinkers are shut off the motorcycle can be started and driven with dead battery. But if the lights or blinkers are switched back on, the bike dies... I can charge the battery or replace it, bike runs fine, but as I said the battery slowly drains until dead.

I read that a battery that drains may be caused by either a faulty AC generator / alternator / stator -and/or- or the silicon rectifier. Based on what else I have read I believe the culprit here may be the rectifier. I do not have any electrical meters, etc... to test these electric components. So here are my questions:

Should I begin to solve the source of my battery drain problem by simply replacing the rectifier? Can someone confirm for me the rectifier is located right behind the blinker / signal relay on the T500? Does anyone have photos of the rectifier so that I can be certain about the component I am looking to replace? THANKS!

[oldjapanesebikes]

You know - with electrical faults, you can spend an awful lot of money buying parts and still not get it sorted, but a cheap meter that will allow you to do a few simple checks can be found for under $20. Its just a suggestion.

[Craig380]

I would second OJB's comment -- I have always avoided electrical stuff on my bikes like the plague, but a couple of months back I bit the bullet, bought a $30 meter and did some easy tests and feel a LOT more confident about how it all works.

It sounds like your charging system isn't working at all, and that could be due to a loose connection, broken wire or a faulty component. You can check this simply by putting the +ve probe of the meter on the +ve terminal of the battery and the -ve probe on the -ve terminal.

If the battery is good, and freshly charged, you should see 12.5 volts on the meter (ignition switched OFF).

Then start the bike and hold the revs about 2,500 - 3,000rpm. The meter should show 13.5V or more. If it doesn't, or shows less than 12V, the charging system has a fault.

If there is a fault, the good folks here can walk you through the process of finding it. A meter makes it REALLY easy.

For what it's worth, a fully charged battery in good condition should give you a couple of hours / 80-odd miles riding IF you don't use the headlight.

[ericsattic]

You guys are right - I just need to buy one of those meters, do the testing, and get it over with. Then, I guess I just need to figure out where and how to start the testing. Clipping the meter wires on battery terminals for voltage testing while the bike is not running - and then while running sounds easy enough. But then after that I may need some guidance! Funny how I always say I'm not an electician and have a bit of a "fear" about electrical work because I know little about electrical systems. Yet on all the bikes I have bought I am always forced to deal with electical issues - but to this point focused on wiring for the headlight, tail and brake light, guages, signals, horn, etc... Well, finally time to take it a step further. Thanks for the help so far but I wil probably be back...

[H2RICK]

Yet on all the bikes I have bought I am always forced to deal with electical issues

Eric, literally THOUSANDS of bikes are pushed into sheds every year and left because of a minor electrical fault......and apparently you've bought a number of them.
Most people with an old/older bike won't put the money or time into fixing what are usually relatively simple problems because they're exactly like you......in the dark about electrical stuff (no pun intended).
Most of this stuff on a bike is direct current (DC) and it very simple to deal with. The alternating current (AC) from the alternator is a little more "interesting" to troubleshoot but it's NOT rocket science, even though it might seem to be.
Humans designed and built your bike so humans can repair it. Purchase of a multimeter is your first step on the road to success.

[jabcb]

Its usually relatively inexpensive to fix electrical problems once you've figured out what is wrong.

The starting point is a multimeter and the wiring diagram. Several T500 wiring diagrams are available online:
http://www.ozebook.com/compendium/t500_ ... 00wire.jpg
http://smokeriders.com/diagrams/Suzuki/ ... Wiring.gif
Two items shown in the diagrams worth noting:
1) alternator has separate coils to run the bike & power the lights
2) separate rectifier & voltage regulator

Start with the tests that Craig380 mentioned. Do the test with the lights switched off & switched on.

If its the rectifier or voltage regulator, relatively inexpensive modern aftermarket parts are available that work much better the originals. Could also be a problem with a dirty switch or corroded connector that you could fix for almost nothing.

[rbond]

If after all your tests don't show any bad connections, test the rectifier. It is a good candidate for the problem you have. Even if you are not confident about the condition of the rectifier, you can get a replacement at Radio Shack for about $3.49. It is '25A, 50V Full-Wave Bridge Rectifiers' Model:276-1185| Catalog #: 276-1185. I have one on my GT500 and so far (2 years) no problems with it. If you replace it and need info on how to connect the wires, ask us here.

[ericsattic]

If after all your tests don't show any bad connections, test the rectifier. It is a good candidate for the problem you have. Even if you are not confident about the condition of the rectifier, you can get a replacement at Radio Shack for about $3.49. It is '25A, 50V Full-Wave Bridge Rectifiers' Model:276-1185| Catalog #: 276-1185. I have one on my GT500 and so far (2 years) no problems with it. If you replace it and need info on how to connect the wires, ask us here.

You know, you guys are just great. I mean that. Heck, if the politicians in this country had the same positive can-do / work together attitude as the two-stroke community board members we'd REALLY have a great country. Don't know why I've always had a fear of dealing with "real" electrical system issues (the wiring things I have done over the years are real simple). But, on the way home from work the other night I went to Pep Boys and finally got a meter. Had lots of fun with it in the garage the other night. I now need to learn to use it better because I am looking at buying a nice 1970 Yamaha R5 350 - and one of the reasons its being sold and at such a good price is because the charging system is not working properly!!! RBOND, your post about the rectifier is great. What I have learned so far is that the three key components are the AC Generator / Alternator / Stator; the rectifier; and the regulator. Gotta run now but will be back with more questions. Thanks again guys, Eric

[H2RICK]

Eric the ONE thing you have to remember about using ANY meter is:

When the ohms (resistance) function/range is selected, do NOT apply the meter leads to a LIVE circuit.
If you forget this rule, and if the meter has a fuse inside, you will pop the fuse. If there's no fused protection (and el cheapo meters usually have no fuse), you'll USUALLY pop the meter itself.
A word to the wise.....

[oldjapanesebikes]

Eric the ONE thing you have to remember about using ANY meter is:

I will never forget my tech instructor in high school telling us the same thing - and that was over 40 years ago so you know he made an impression - his opening line was: "if you want to avoid copper plated eyeballs ......."

[ericsattic]

Eric the ONE thing you have to remember about using ANY meter is:

When the ohms (resistance) function/range is selected, do NOT apply the meter leads to a LIVE circuit.
If you forget this rule, and if the meter has a fuse inside, you will pop the fuse. If there's no fused protection (and el cheapo meters usually have no fuse), you'll USUALLY pop the meter itself.
A word to the wise.....

WOW! What an electrifying post... been busy this week but hope to find time this weekend to do some testing - very carefully!

[ericsattic]

Finally got a break from work and family obligations and fired up the bikes today - '70 H1, '70 T500, and last but not least the '68 T500 Cobra: the one with slow battery drain. So here are the various voltage readings I took - real anxious to get some feedback from the board =

12.5v : Ignition on, charged battery 2+ weeks ago and bike sat two weeks not run
11.97v : Warmed-up and running steady @ 3000 rpm
11.94 v : Warmed-up idle @ 1500 rpm
11.75v : WITH LIGHTS ON while running steady @ 3000 rpm
11.6v : WITH FLASHERS ON while running steady @ 3000 rpm
12.15v : With bike now shut off; note the voltage slowly ticks up with bike off and after just a couple of minutes the voltage reads 12.3v...

Obviously there is a major drain via the lights and flashers. I do use those when I ride for safety. Any thoughts from the the electrical experts out there?

[ericsattic]

* UPDATE * UPDATE *

Thanks guys but I believe I found the source of my battery drain problem. Long story short for you T500 owners: among the wire harness leading from the generator back towards the battery are many different colored wires including a yellow and black one. They are supposed to be hooked up to similarly colored wires coming from the rectifier. But in my case, they were reversed: the yellow wire from the generator was hooked to the black wire from the rectifier and the black wire from the generator was hooked to the yellow wire from the rectifier. I connected the wires to the correct colors and voila! Voltage Meter readings in the 13v to 14v range with the bike running - and with the lights and flashers on! THANKS AGAIN to all and I will keep testing after rides and post updates if necessary. Oh, and as I said - I am no electrical expert, but I know how to connect wires of the same color. I DID NOT do the wiring on this bike! Sorry to bug you all about this embarrasing situation but it has been a learning experience. Also, if anyone wants an EXCELLENT description of an electrical system on these old bikes, etc... take a look at an official Yamaha R5 Service manual... way better than what's in the Suzuki T500 service manual, Hanes Suzuki T500 manual, Clymer Suzuki T500 manual, etc...

[Craig380]

Ha, it's great you've got such a simple solution ... all set for the summer!