2000fatboy battery charging system

Hello, sorry to hear you are having trouble with your bike. There are a few things that can cause the problem you are experiencing but since the Speedo is changing modes I would suspect that your system voltage is dropping below its normal value. I would begin by making sure that your battery is fully charged and that your charging system is putting out its rated voltage. To do this take a volt meter and check the voltage across the positive and negative of the battery terminals with the ignition switch "off" you should see about 12.5 volts. Check the battery with the ignition switch "on" and see that the voltage remains about the same. If that checks out ok then start the bike and with the with the engine running you should see at least 13.5 volts. If the battery and charging system check ok then there may be a problem with a control module or sensor which will require further trouble shooting. One thing you can do to reset the control module in most cases is to disconnect the battery and let the bike sit for 30 min. Next reconnect the battery and check for faults. Good luck! This is a link to the service manual for your bike:
https://www.scribd.com/document/238034580/GV250-GT250-EFI-Service-Manual

Let's start by taking the battery out and taking it to an automotive part store. Ask them to load test the battery for you. They'll usually do this for no charge. If the battery test good, put it back in the bike and make sure it's charged up fully.

Now, connect a DVOM (digital volt ohm meter) to the battery. Red meter lead to positive, black meter lead to negative. Put the meter function knob on DC Volts, 20 volt or greater range. Start the engine and bring it to a high idle. You should be reading 14.5-14.8 volts across the battery. If not, check the output of your alternator.

Unplug the regulator down at the cases just to the left side of your oil filter. Look down into the connector and you'll see two pins. Put your meter's function knob in AC Volts, 50 volt range. Start the engine and bring it to a high idle. Touch one lead of your meter (either lead) to one pin and the other lead to the other pin. You should be reading thirty volts or more.

If not, you probably need to replace the stator in your alternator, If you read 30 volts or more, replace your regulator.

Now, as to whether or not this will correct your speedo problem, I have absolutely no idea.

Good Luck
STeve

First, charge your battery to full charge. then, using a digital volt ohm meter connect the red meter lead to the positive post and the black meter lead to the negative post, put the meter in the DC voltage, 20 volt or greater range. Start the engine and bring it to a high idle. You should read 14.5- 14.8 volts. If not, your charging system is not working.

Next we check you alternator. At the front of the engine case, find the connector where the voltage regulator connects to the alternator and unplug the connector. Look down into the connector on the case and you should see to metal connectors. When we get ready, we're going to insert one meter lead into each metal connector. It makes no difference which lead goes to which connector. Put your meter in AC voltage, 50 volts or greater range. Very important, make sure the meter is in AC voltage range. Now, start the bike and bring it to high idle. Insert the meter leads, one into each connector. Make sure you do not touch the engine cases. You should read 30 volts or greater. If so, you alternator stator is fine but your regulator is probably bad. If not, your alternator stator is probably bad. Once you determine where your problem is, repost and we'll tell you how to repair it you wish to do the job yourself.

Good Luck
Steve

first thing i think i would look at would be the wiring connections for the battery. CHECK AT BATTERY AND THE OPPOSITE ENDS OF EACH CABLE. if these are good, maybe check your charging system. sounds like it could possibly be failing. start bike and allow warmup. disconnect battery ground cable and see if it still runs. if it cuts off immediately, your charging system has failed and you'll need to determine the cause and correction.

Check the battery contact. Or check if the battery is good.

would change the ECU with the chip from the key from a car in scrapyard ,but before you get carried away try another seperate earth on the back of the speedo printed circuit board ,i wouldnt mind betting this is your problem

yes thats a good place to start-always check wiring 1st-sometimes things that appear normal can be corroded but i think your alternator battery or regulator is failing-test it dew u have a manual!!

It means your bike has recorded an trouble (error) code. depending on the year of the bike you can get them to display on the speedo or you will have to have Harley or shop find out what the code(s) are.

The first thing I would check is the voltage output from the charging system. If the regulator isn’t regulating, the voltage will keep climbing as the engine speed increases. The electronics in the speedometer don’t work well at these high voltages. This would also explain the bright marker lamps. You should be able to see this with a simple voltmeter across the battery terminals.