On '97 fat boy heard a pop under the seat and will not start. also with 12 volt check light hooked to battery, it goes off when ignition is turned on,

put a multimeter on the coil wire , set the meter to 12 volts dc and turn on the ignition
it will be either 12 volts ( 12volt coil ) or 7.5 volts ( 7.5 volts coil)
this system is used on may electrical ignitions meaning it starts on 12 volts ( maximum spark with reduced voltage under cranking ) but runs on 7.5 volts ( resistor controlled voltage )

Check the wiring under the rear fender for damage. Check the bulb by replacement. Check for 12 volts at the rear brake light switch. Check for blown fuses.

Well, I don't really know how to tell you to troubleshoot your starter when you don't have a meter. When you press the starter button, there is a starter relay that is usually mounted on the rear fender extension on the Fat Boy that engages and provides voltage to the starter solenoid. This voltage goes to the solenoid via the single small wire that plugs onto the starter just above the d-sided plate on the end of the starter. This wire goes hot which energizes the coil in the solenoid. The magnetism pulls the plunger into the starter. The plunger has a large round copper "washer" that make contact to two copper terminals inside the solenoid that connects the battery to the starter motor.

To test the starter, make SURE your transmission is in neutral. Take the 5-sided plate off the end of the starter. There are three 3mm bolts that hold the plate on. Behind the plate, you'll find the plunger and long spring. Using a large screwdriver or something, push the plunger into the solenoid as far as you can. The starter should engage and turn the engine. If not, look at the copper contacts inside the solenoid. If they look burned and are not smooth across the face, you may need to replace them. Rebuild kits are available both through Harley and aftermarket suppliers.

Good Luck
Steve

First, take your battery somewhere and have it load tested. Fat Boys are tough on batteries as the battery sits in the "horseshoe" oil tank and is subjected to high temperatures due to the hot oil in the tank. Battery life is typically two years although I've seen some go longer and some not last that long. Have the battery tested before you start spending money.

To check the stator, you unplug the regulator at the engine case. Down inside the plug you'll see some electrical connectors. Connect a DVOM (digital volt ohm meter) to these connectors (one lead to eac pin) and put the meter in the 50 volt or higher range AC voltage. This is important that your meter be set to measure AC voltage because at this point, the voltage is indeed an Alternating Current voltage coming out of your alternator. Start the engine and bring it to a high idle. You should be reading over 20 volts AC. The book says that you should read 12-18 volts per 1000 engine RPM. If your engine is turning 2000 rpm, your meter should read 24-36 volts AC.

To test the regulator, first charge your battery to a full charge. Then connect your DVOM across the battery, red to positive, black to negative. Put the meter in the 20 volt DC range. Start the bike and bring it to a high idle. The voltage will start at somewhere around 12.5 volts and climb to about 14.5-15 volts. This would indicate that the regulator MAY be alright.

Now, have you changed any of the lights on your Fat Boy? I've seen people change and add lights to the point where their alternator could no longer put out the current necessary to handle the load. If this is the case, you may need a higher out charging system.

I don't know where you're located but $260 seems quite high for a voltage regulator.

Can you do a hydro check on the battery? Should be near 1200. How about the volts? Should be very near 12. When it is running, what kind of volts do you get. Should be 13 or more but not above 15.

Id check the solinoid (sp). They do burn ... When it clicks, check voltage on the starter side. (the starter side will be dead when the start switch is NOT pressed.) If you have the same as on the battery side, id look at the starter (if you can find it ;-)

I hope this helps ... Hope you get it going.

thanks

a

well i would make sure all ground from battery are tight and clean then check pos cable to be tight if they seem to be good the make sure you have 12 volts or more at battery then on that model the ignition is on the tank the ignition very common to go out if it is the type on the tank you may need to pull cover on tank to get to ignition to test very simple to remove cover and test the wire make sure you getting voltage when you but it to start some time wiggling switch you can get it to work hope this help

the battery says 12 volts but may be dropping to 4 or 5 under a load...i would suggest jumpstarting the car and see what happens.the battery should read in the high 12 volts and not less than 9.5 under cranking. the dash lights go out on your car when starting,and the alarm will go off ,and disable the ignition if the voltage is too low in cranking the car because the computer will shut it down and activate the anti theft.....check your battery posts are tight. best of luck

There is a "starter" solenoid that closes when the ignition key is turned to the start position.
Follow the positive (red) battery cable from the battery post to the solenoid. If you have a 12 volt test light or volt meter, check to see if you have 12 volts on the battery side of the solenoid then turn the key to the start position and see if you have 12 volts on the starter side of the solenoid.
I believe you have a starter solenoid that has gone bad.
Good luck, let me know.
Regards,