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Any super-techs around on a Sunday: voltage drop.

  • Thread starter Thread starter Karl
  • Start date Start date
K

Karl

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My GS has a gauge package in the fairing. When I bought it, the voltmeter indicated about 10 volts when the bike was running. I had no idea as to the accuracy of the gauge, so I didn't worry about it and rode blissfully for two summers.

This summer, the gauge went out completely, so I tore the fairing up and found a ground problem and fixed it. The gauge again shows 10 volts when the bike is running (about 8.5 when ignition is on but bike isn't started).

I checked the accuracy of the gauge against my handheld voltmeter and it is right on!

So...I have to assume this isn't a perfect situation. The battery shows 12 volts at the posts.

Is this a:
Battery problem.
Charging problem.
Wiring problem.
Other problem.
No problem????

I'd appreciate any advice as I an fixing stuff to make sure all is OK for extensive riding with the spouse.

Thanks...great forum!
 
I am not a super-tech, but I did stay at a Holiday Inn Express last night.

If your battery reads 12V while your gauge/meter reads 10V, then you're seeing a loss in the wiring harness somewhere. Check all the connectors between that gauge and the battery - clean em off (fine sandpaper works) and double check the grounds the same way. You should have good clean connections all the way through. You can also use your meter to check voltages at various connectors along the way to try to isolate where in the harness the problem is located.

If your gauge and battery drop at the same time (10V both places) then the load on your battery is draining it and it's dying. It's not uncommon for a dead/dying battery to show 12V under no or meter-only load and drop once you put some strain on it. My concern is that your battery only reads 12V - is that when the engine is running?? It should be higher than that (like 14V) while it's running otherwise the charging system might not be pulling its weight. Most of the tech manuals have the procedures to check the charging system and isolate problems there.
 
Thanks, Brian.

I'll do some more checking today. At this point, I haven't checked the battery voltage while running yet. The family was still asleep ;)
 
At idle, the battery reads 13 volts at the post. The gauge reads about 10.5. I can't find my service manual. One of the kids must be using it as a coloring book :(
 
Well, after blowing a 15A fuse and causing a little smoke at the gauge cluster, I have determined that all positive wires in the fairing are carrying 10.5 volts with the engine running. I am in the process of cleaning all connections between the bike harness and the fairing harness.

When checking the turn signals, I notice (engine off) that he headlight dims a little when the signal flashes on. Is this another indication a new battery may be in order?
 
I would first of all suspect an earth connection. Its quite easy to prove, just jump the earth (negative) directly to the voltmeter negative from the battery negative terminal with a direct wire. If it improves just find the connection and clean it.
If it does not improve, do the same with a positive feed, but be carefull here as your meter is most likely feeding from battery via main fuse, via ignition switch, back to the fuse box, via a switched fuse, back to the front and picked up there and such a long route may easily have a problem in it and I would suggest you follow it using the wiring diagram. I would use a direct wire with a tempory fuse from the battery positive and then if the meter shows correctly, just walk the jumper back on that feed until the problem shows up and you have it.
This is only how I would do it, if you are new to electrics be very carefull or get someone to help you!!:)
 
This is where your voltmeter can be your best friend.

If you have a small battery charger, connect it to the bike, as you will have the key turned on for quite a while.
It is also good to disconnect the headlight fuse for the duration of the testing.

Clip the black wire of your meter to the negative terminal of the battery. Check the voltage at the positive terminal. Just for argument's sake, let's say it's 13 volts. If your bike's meter is working, check the voltage at its positive terminal. If it is also 13, you have a ground issue. If it's not 13, you have a power issue. (You might also have a ground issue, but you definitely have a power-side issue.) Follow the wiring from the meter back to where it is getting its power, looking at connectors and checking the voltage at each one. Somewhere, you will find your drop.

When you finally get battery voltage at the meter terminal, check to see if it reads correctly. If it does, great, you are done. If not, follow the meter's ground wire, checking all the connectors, looking for a voltage drop at them, too, just like you did on the power side.

It is not uncommon for a meter's source wire to be a couple tenths of a volt below actual battery voltage, but over TWO volts is entirely unacceptable.

.
 
Yikes! :eek: That's how I blew the fuse.

I will try a direct connect to ground. I directly connected the pos. battery post to the meter and blew a fuse (on completely seperate accessories) and started the gauge light smoking.

However....I will try a neg. post jump (I was a little skitterish after the smoke), to see if I have a bad ground somewhere.

Thanks!
 
A direct ground to the battery negative did not change the gauge reading. When I unhooked the jumper, the needle twitched, so I know it did something, but the gauge did not read considerably differently.

Is this a related issue?: I noticed this morning about half the top of the battery was a little wet and greasy. I have heard of boiling a battery before, and did have it on the trickly for a considerable amount of time yesterday, so I dismissed it. This symptom is not going away, and after the negative jump, I can hear some popping from the battery.

Am I boiling my battery fluid somehow? Is that related or unrelated?

For those of you wondering why I don't just put in a new battery and dispose of that point...we're dirt road poor :(, but I'll put in a new battery if that's the problem.

Thank for all the help.
 
The good news is that if you are reading 13 volts at the battery at idle, your charging system is probably healthy.

Two suspect sources for the voltage drop are the ignition switch and kill switch. Both switches have small contacts and tend to drop a significant amount of voltage. There is a relay mod that uses the ignition switch to pull a relay that then supplies voltage to the entire system directly from the battery, bypassing the ignition switch. I have done this mod to two GS bikes and both time the voltage to the system rose over a volt.

Another tip is to clean all the connectors with something like Caig DeOxit and then use dielectric grease on the connectors to keep them conducting well.

Thanks,
Joe
 
Lets cut to the issue at hand, you have a voltmeter mounted some distance from the battery.

Disconnect the voltmeter wire from the battery and measure the resistance (including the terminal) to the meter. Do this for both meter leads. If you measure more than 0.5 Ohms you have found your problem.

Replace the wire.

If not, then the voltmeter is not connected to read the batter voltage but is reading some other voltage that probably is 10 volts.

This is most likely your issue, and can be modified by relocating the point at which you measure. As was posted earlier, the Kill switch will eat up some of that voltage if the contacts are not really clean, you have associated wiring resistance that contributes to the voltage drop and the contact resistance of where the wiring harness terminates to its various components.

So, if you want to read the correct voltage, then you can either clean up the contacts, wiring etc... move the voltmeter leads to measure the actual battery voltage, or mentally add about 2.75Vdc to whatever you see on the voltmeter.

Sounds as if the bike is charging, is starting, no wires are getting hot when she is running, right?

If so, you can get by without a worry.
 
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