Fun with the electrical system

I have on and off problems with the battery dying after sitting unused for 2+ weeks. I am wondering if this normal, if my charging system might be bad. Should I just spend the $70 and get a new battery. The bike also seems to want to die at idle (is stoplights) as well. I am thinking this is all related to the fact that my bike sat for 5 weeks while the tank and fenders were getting painted. I am also thinking about picking up this battery gauge as an add on for the bike.

Thanks for the advice,

David Socha

 

I definately like the idea of a voltmeter on a bike.....take your battery to a parts place and have a load test done on it....and if you have a multimeter check the voltage across the battery with the bike off...the closer to 13 volts the better I think. Then check it at a 2000rpm idle I think 14-14.5 volts is optimum.

Im sure the guys really in the know will get you the right numbers soon, but this should help you get an idea of whats happening.

 

How old is the battery? You'll only get about 3 years service out of a battery nowadays.

A static battery in GC should read around 12.8V. Put the voltmeter across the terminals whilst the bike is running and you should get 13.5 - 14.5V.

 

check the voltage AFTER the fuses, at idle, with your foot on the brake. the dying at stop lights could be resistance at the fuses (or elsewhere) creating too much voltage drop under the "high" load of the brake light, headlight, and engine running. if it drops below ~8v, the bike will die.

did you check the water level in the battery? are the terminals corroded?

sitting for several weeks shouldnt be an issue unless there is a draw. you will need an amp guage or meter with amp capabilities to check for draw. you should have 0 amps draw with the key off.

 

The battery is an AGM battery that was purchased about a year ago.

The static read was 12.63V, so I have the battery on the charger right now. When the bike was running with throttle, Voltage across the terminals read about 12.9-13V. If someone could post a picture of where exactly the fuses are that would be great. The bike is an 85 XJ700N. On a related note, might this be an alternator issue, and how might I begin to diagnose that.

Thanks,

David

 

Under the seat on top of the air filter, in a box marked fuses.
Take the cover off the generator, large round cover left side, under carbs & check the brushes, there is a line marked on the brushes, if they are worn down to that line replace them.

 

Thanks. I will look into that ASAP

 

Any one know how to test a TCI unit on an 85 XJ700. Or can anyone direct me to a forum post that has the instructions. I am only getting about 13.7-13.9 volts out of my charging system and I need to be getting 14.0-14.5 at a minimum. This is voltage at the battery terminal, with the bike revving at over 2000 RPMs. Checked the alternator and that seemed to be good.

Thanks

 

TCI doesn not regulate the charging system, the regulator-rectifier unit does (it's the finned, square box located next tot he TCI unit).

You really need a service manual in order to check it, there is a rather lengthy, involved series of tests to make sure that all of the internal components are operating properly.....or you can substitute a known good one from aby XJ550 - XJ900 model, they're all the same.

How did you check your alternator to determine that it's "good"?

 

I was just about to order the XJ CD. Assuming that has descriptions of the necessary tests, I will re-run them after I get the cd / login. I think that I tested the alternator correctly. Checking the 3 white wires coming off the stator at the wiring harness, I read resistances of 0.8 Ohms. That happened when I checked White 1 to White 2, W1 to W3, and W2 to W3. The brushes on the alternator are now where near the line, so those are good. I had problems checking the rotor resistances. I am hoping that i don't have to replace those parts, as the $400 is something I could definately use elsewhere on the bike.

On a related note, at this point I think I may have fried my AGM battery, so I am going to use it until I get this charging system figured out and then replace it with something new.

Thanks for the help,

 

Why does fixing electrical problems always feel like chasing your tail?????

Now on to the real question, does anyone have any idea where to start looking when the ignition system, key, gauge cluster, headlights, etc get no power when the key is turned on.

Before anyone asks, the battery is good and holds a charge, the generator is putting out the necessary voltage, and the electrical system seems to be functioning fine otherwise.

Thanks,

 

Undo the Headlamp
Get inside the Headlight Bucket
Find the Pigtail from the Ignition Switch.
After you have made a 3-way jumper with mini Alligator Clips.

Jumper the 3-Terminals in the Harness.
See if this brings Life to the Bike.
Yes: >> Bad Ignition Switch
No: >> Trace the RED wire back to the Battery until you find 12V

 

Thanks for the quick reply.

I am hoping this fixes 4 years of "Phantom" electrical problems