Brake Warning Light

This is the first of a few posts.

I have a 1982 XJ750 Maxim. Last year the BATT light would stay on at low rpm's. I found the stator connector under the seat was arcing and replaced it. Blades and terminals were also replaced. Now the battery is on constantly.

Thanks

 

I have a 1982 XJ750J Maxim. The brake warning light comes on occasionally. Any ideas where I can start first?

I rebuilt the MC last year and that looks good.

Thanks.

 

Someone correct me if I am wrong but I thought it was the battery fluid level, that if low, turns the light on.

 

That is correct, unless the mod has been done to turn it into a batery voltage monitor.

OP, has that mod been done, or is the battery level sensor still hooked up? The level sensor screws in to one of the battery cell caps, and hooks up to a white wire with a red trace.

 

When I received the bike year before last there wasn't anything screwed into any of the cells in the original battery. That doesn't mean it's not there though. I'll take a look and update the thread when I can determine if it might be tucked in the back.

 

If there's nothing connected to the battery cells, then the sensor is long gone and not hooked up. Your battery light will always be on unless you do this:

http://xjbikes.com/forums/threads/battery-sensor-we-dont-need-no-stinkin-battery-sensor.820/

 

Thanks for the information. Much appreciated.

I have a Yamaha battery but it has push in caps. I have to do some research to see if I can find a battery that will fit that has screw in caps. I want to get this bike working like it did coming out of the factory so this is essential.

 

The sensors are still available through Yuasa, and can be fitted to the battery you have.

 

Roger, you should keep your electrical questions connected in one thread.
Cause they very well maybe connected.

The flashers - pretty sure you need to verify that all 4 have the correct watt bulbs in them (24w?). An imbalance of watts / current draw will make things funny.

 

add brake fluid?

 

Great. I'll check that out first. Much appreciated.

 

That's good to know. From what I read it's stated that I needed screw in battery caps.

 

Merged. The second post is from the second thread.

 

I just use an appropriate size tap to thread the hole for the cell cap. Do it before you fill the battery and make sure you get all the plastic bits out of the cell before you fill it.

I got my battery fluid level sensor from a Yamaha dealer about 6 years ago, before I found this site and Xj4ever.

 

You can also press the button to reset everything each time you start up......

 

sorry to jump on this thread,i have fitted a 2.2k ohms 1 watt resistor and the warning light remains on.battery reads 12.55v and at 2k revs 14.25v

 

I used 2 2.2k ohm 1/4 watt resistors on mine. Which wire did you run it into?

 

you are at the 10% over value mentioned 2K ohms in the thread. read voltages on both sides of the resistor what do you get?

 

did it work?
did you run them in series or parallel?
parallel would make it 1.1k ohms 1/2 watt
series would make it 4.4k ohms still 1/4 watt.


82 xj750 wiring diagram shows it as a white /red wire that runs up to ignition switch and then to computer.

the other end of resistor would go to the + battery terminal
then check the voltage drop on the resistor white/red wire

 

from xj4ever catalog
What about my original battery fluid level sensor?:

Also, the sensor reads voltage, and without enough voltage to trigger the computer system, the light illuminates. The wire path from the sensor goes through your ignition switch and if this switch has electrically "dirty" internal contacts, then that can add enough resistance to cut the voltage signal enough to trigger the dash "low Batt" warning light or display, even though the sensor is fine and the fluid level is okay! So: remove the ignition switch, and its bottom plate, and clean the copper contacts inside the ignition switch.

this is what you need to
http://www.xj4ever.com/HCP14180 battery sensor bypass.pdfread

 

i am not very up on electrics what do you mean by [series or parallel] i have fitted one resistor to the white/red wire and the other end to the + battery terminal.will check tomorrow the voltage either side of the resistor.

 

my response was to crazynat post of 2 resistors at 1.1k ohms.

series is 2 motorcycles driving down the road one behind the other ( one end of resistor soldered to the end next resistor)

parallel is 2 motor cycles riding down the road side by side ( resistor side by side leads at each end twisted to gether)

 

one side ,battery side will be 12 volts the side to white /red wire will be less.

 

It worked for me, I ran them in series into the tail light our brake light wire. I've had it like that for a year and no problems, even got to test it earlier this year after the battery had been sitting. It was low and the light came on until I got it charged back up.

 

sounds good as the resistors convert it to a voltage tester. could be OP has to charge his battery.

 

update.battery voltage at resistor when running is 2.7v.sometimes the light goes out when started other times it stays on.not been out on the road yet but will see when i do and report back.

 

sounds like your battery is weak/old or just needs a good charging
sounds like the resistor setup is working properly.
you should check your charging voltages and your battery at rest after it sits over night.
How are the acid levels?
use distilled water to bring them up to level

and once again info from has good info on electrical and the charging system well worth the read as it tells what to look for if things are out of spec
The Ultimate Relay, Switch, Sensor, and Diodes Guide

Starting Load Test:

a) Adjust voltmeter to DC volts (20 volt range).
b) Place voltmeter leads to the battery terminals (positive to positive and negative to negative) .
c) Watch the voltmeter as you start your motorcycle, but before the engine is running.
d) If the voltage drops below 9.5 volts, the battery has very low capacity and should be replaced.


Charging System Tests:
For all XJ-series models, the maximum available charging output VOLTAGE should be as follows (all values are approximate):

* approximately 500-2000 rpms: 1.8 volts gradually increasing to 14.2 volts
* 2000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all models except XJ700-X and XJ750-X)
* 3000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all XJ700-X and XJ750-X)


Static Battery Voltage Test

Prior to conducting this test, make sure the battery has not been
recently charged. You must wait at least one hour after charging
your battery to conduct this test.

a) Adjust voltmeter to DC volts (20 volt range).
b) Place voltmeter leads to the battery terminals (positive to positive and negative to negative).
c) Read voltage and refer to the chart below.

State of Charge:

100% Charged with Sulfate Stop:
Using a syringe Hydrometer: 1.280
Using a Digital Voltmeter: 12.80 volts
Using a Floating-Ball Hydrometer: 5 balls floating

 

xj550H thanks for all the very good info will check it all out.

 

Is that a typo?

 

the resistor thread said it should be kept under 5 volts
2.7 may be the connector side of the resistor not the battery side.
voltage drop across the resistor.

robbo did say it was turning warning light off sometimes.
we need more data from people who have done this.
resistors used voltages ect...

going to buy me some resistors and check it out .


it would also be nice if those with the original style sensor could post some connector voltages

 

I can check mine if that would be helpful. Where exactly did you want the measurements?

Also, if you want some of the resistors I got you're welcome to a few. I got 25 of them because it was cheaper that way.

 

Some thought and speculation as I see it and subject to change as noted by the XJCD or other knowledgeable members. Note I have been running with the 5.6k resistor for the past month with no issues noted.

The original battery sensor installed in the 4th cell from negative battery supplied approximately 6.4 volts to the CMS for battery monitoring - 3x a fully charged battery where each cell would equal approximately 2.13 volts. The original setup was mainly a check for electrolyte level as the voltage decrease to set a fail would equate to a battery voltage of 6.6 volts, well below a useful voltage monitoring spec.

Installing a 2.2k resistor is really only useful for eliminating the battery warning, as that value combined with the internal components of the CMS would not detect a battery low voltage until the battery dropped to approximately 5 volts. Once again too low to be considered a useful voltage monitor.

The more appropriate size of the "bypass" resistor with wiring and switches that are in good working order is 5.6k, which will set the battery warning at approximately 10.8 volts, a warning that would be set in time before the bike would stop running from lack of voltage to power the TCI and ignition coils.

This is really close to what it should be. With no wiring / switch issues the calculated voltage using a 2.2k resistor is 2.88 volts at a battery voltage of 12.8 volts. If the battery warning is intermittent with the resistor then the most likely cause is what Len mentioned earlier, a downstream issue with the ignition switch contacts or wiring causing a momentary open or increased resistance. This should also be visible in the failed condition as a voltage much higher than 2.7 volts. A solid reading of 2.7 volts or so with the constant battery warning would be a bad sign as it would point to internal to the CMS.

CMS internals:

 

That makes a whole lot of sense. I got to re-thinking the resistor value myself this afternoon, but hadn't the time to work things out to determine the voltage needs.

Rooster, would you mind adding you post and schematic to the original bypass thread?

 

This thread?

http://xjbikes.com/forums/threads/battery-sensor-we-dont-need-no-stinkin-battery-sensor.820/

 

Yes.

 

update,battery voltage 12.55 when cranking drops to 9.2v.Went for a run of about seventy miles, light was on when started but after about two minutes of riding went out.I stopped five times shut off and restarted, each time light was on and went out after about two minutes of riding.Do you think i should now try the 5.6k resistor as mentioned.hope this is of use.

 

I think you should try a new battery.
Your systems monitor was telling the truth.

Changing to a 5.6K resistor would be a good thing IMHO.

 

Get a voltage measurement of the 2.2k resistor output during the failed condition if you can. Hopefully, it will be considerably higher than the 2.7v that you noted earlier and will be the result of a poor connection at the ignition switch connector or the 9 pin connector to the CMS, or just needing to clean the ignition switch. Or, better yet, it would read zero on the output side which could indicate a poor connection in the resistor installation.

 

update,battery voltage 12.55v(not used for 4 days} in failed condition{warning light on} 12.20v at resistor after about 2 minutes warning light goes out and voltage at resistor is 2.70v.so should i check for poor connection at ignition switch connector and cms connector.

 

You should get a new battery. The warning light is going out because the alternator is charging the battery back up to an acceptable voltage, but it is dropping below an acceptable voltage when you start the engine. The resting voltage is also low.

 

ok thanks for all the replies i have had,will get a new battery when funds allow.

 

Yes, and although the battery is not in the best condition, remember it would have to drop to 5 volts to cause a battery fail when using a 2.2k ohm resistor. So, try this since you seem to be able to duplicate the problem after sitting for a while:

Disconnect the battery positive terminal from the battery
Turn the ignition switch to on
Connect the negative lead to chassis ground, battery negative will work or a good chassis ground
Connect the positive lead of the meter to the output of the 2.2k resistor, the W/R wire, you should get a reading of very close to 650 ohms
If the reading is high (it will be unless the issues is a poor connection between the output of the resistor and the W/R wire), jiggle the ignition switch while observing the meter and look for it to go lower. If no joy, then open the headlight bucket and locate the ignition switch and CMS connectors mentioned earlier and disconnect, inspect, clean, and reconnect.
If still no joy back probe the 9 pin CMS connector at the W/R wire to chassis ground and see if you get the 650 ohms.
If the last step is the only time you get 650 ohms, then start looking for the loss of continuity through the wire harness or ignition switch.

The .35v voltage drop from your battery voltage to the output of the 2.2k resistor indicates you have around 77k of resistance downstream from the output of the 2.2k resistor.

 

update,have tried all the above and get no readings at all except when i back probe the 9 pin cms connector and get a reading of 1.245 [voltmeter set at 2k ohms].I have now put a 5.6k ohms resistor in and the output shows same voltage as the battery and the warning light is on,although i have not been out for a run.sorry but electrics is like a black art to me.

 

OK, so lets try something that is quite simply, a continuity check from the W/R wire at the battery to the W/R wire at the CMS.

Disconnect the battery negative and positive just to be sure no voltages are present to interfere with the reading.
Set the DMM to a low reading, like 200 ohms.
Touch the leads together, this is what each of the following measurements should look like - a short or continuity.
Place one lead of the DMM on the W/R wire at the 5.6K resistor output.
Locate the W/R wire at the input to the 2 pin ignition switch connector and back probe it, should get continuity
Place the ignition switch to "ON" and back probe the W/R wire at the output of the 2 pin ignition switch connector, should get continuity
Locate the W/R wire on the 9 pin CMS connector and back probe it, should get continuity.

Let us know the results.

1.24K is a bit high, but....

So not sure I totally trust the reading. If you have a couple of resistors laying around use them to familiarize yourself with how the meter works.

 

update,went out last night to a bike meet 20 miles away,on start up warning light on, after a few yards light went out and stayed out.on return journey on start up warning light on, and stayed on all the way home.this morning carried out the check by rooster53
w/r wire input 2 pin ignition switch=continuity
ignition on w/r wire output 2 pin ignition switch=no reading
w/r wire 9 pin cms =no reading

 

Looking like a bad ignition switch. Check continuity on the switch itself, in to out on the W/R wire and you should get continuity in the "ON" position. You could temporarily install a jumper on the harness side also as a troubleshooting aid. The drain on the battery would be very minimal if left there temporarily.

If you isolate it to the switch then there is this, hopefully a good cleaning will put things in order:

http://www.xj4ever.com/clean and lube the ignition switch.pdf

 

thanks, will check it out at the weekend.

 

eureka it works.there was no continuity between the w/r wire at the ignition switch,so removed ignition switch. only had to remove headlight bolts and the cms bolts to remove ignition switch,did not even have to remove speedo cable,a bit of a struggle but not to bad.cleaned the brass contacts [did not look to dirty] and had continuity.put all back together and on start up the light went straight out.i would like to thank for all the help i have received mostly rooster53 and that this thread is of use to others in the future.what a great site this is.

 

update,since cleaning the ignition switch and connectors the bike starts as soon as you hit the button,before if you had not started it for a few days it would crank for a while before starting and in the winter would sometimes not start at all.

 

went out for first run since last year,about 50 miles, for the last couple of miles the battery warning light came on.have a resistor fitted {see above} and understand this now works like an ammeter,low voltage light will come on.checked and cleaned all connections from the alternator, put multimeter on battery 12.8v started bike over 2k revs sometimes shows 14.5v sometimes 13.3v tried it quite a few times switching the bike on and off a few times and still get different readings.the battery warning light is on all the time,have replaced the resistor and still the same.any ideas to point me in the right direction?