Battery not charging. Once started I disconnected the positive battery lead and the truck dies. Is it the altenator or is there a fuse or relay that could be the problem? Battery connections are clean and well maintained.

there is a power leakage in the electrical system
disconnect the earth cable from the battery and place an amp meter in the circuit ( terminal to lead end) and check for current reading. the amount of current flowing will give an indication of the drain and what is likely to be still on. ( glove box light,boot light,interior light,relays,fuel pump, faulty ECM radio amp or booster diode in alternator etc)

I would check your ground from the battery to the frame/engine and also the positive battery lead where it connects to the starter/relay

The easiest way to check is with the car running, disconnect the positve side of the battery, if the car dies, then it is the altenator, if the car keeps running then it is the battery. If you have a volt ohm meter, check the chrge going to the battery you should get between 12 and 14 volts if it is lower than 12 you have an altenator issue. the altenator should always produce enough to charge the battery and run the car at the same time, if not then the battery wears down.

First off, DON'T pull battery cable when running. That used to be the way to test charging systems years ago, not these days. Hopefully you didn't destroy your new alternator. IF, you have access to a volt meter, with car running put leads in each battery terminal you should have voltage at 13.1v - to 14.8v, Anything less, your alternator is bad. If it tests ok, then someone either missed a lead on back of alternator or one of wires is pinched.

Replace the altenator. It has gone bad and every thing is running on the battery.

sure!can you charge battery? if won't start charge the battery and take it to nearest autozone or advance auto parts and as long as your check engine light is on,,, they will code read for free, then they will tell you what or where problem is.if not then try this,,,put in fully charged battery,start it,,disconnect the positive cable from battery while engines running,careful not to let the positive cable come in contact with any metal of car, if engine dies,,altenator not charging,may be bad diode in back of the altenator or blown fuseable link inbetween starter and altenator.hope this helps and if so please note so in response. thank you for choosing fixya.com

you can have your altenator tested at an autozone,advance auto for free while it's still on the car,or you can check it yourself by starting the car,while running disconnect the positive cable,be careful not to let that cable touch anything. if the car dies,the altenators bad. as far as a fuse, you may have a fuseable link,but those are usually for the starter.someone may have done some other wiring to it.i would check the altenator first though.also make sure your belts tight and the altenator is plugged in. check the plug on the altenator to insure it's plugged in all the way.make sure your battery cables are tight. if you decide to go to a parts store to have the altenators good,have them check your battery also. it's free.if your car runs fine until you park it at night and then next morining it will not start,it may be bad battery.just thought i would throw that in,just in case.hope this helps and thank you for choosing fixya.com

the voltage regulator is built into the altenator,if you are having a charge problem, theres an easy way to check to see if it;s charging, while the engine is running disconnect the positive side post of battery, careful not to ground it to anything metal, if car dies,no charge from altenator, if it stays running,reconnect the positive post, if not you'll need to leave that disconnected to replace that altenator.if you need further assistance from fixya please post your question and we'll be happy to help you.thank you for choosing fixya.com!!

COULD BE BAD BATTERY POSITIVE CABLE.BATTERY FEED WIRE FROM THE POSITIVE BATTERY CABLE BROKEN.YOU COULD HAVE POOR GROUND.YOU COULD HAVE BLOWN ALTERNATOR FUSE LINK OR FUSE BLOWN.CHECK ALTERNATOR FIELD WIRE OR BATTERY FEED WIRE FOR BROKEN OR DISCONNECTED WIRES.

Check the cells on the battery, if they are dry or not full of water then they can go bad. That would incorporate the battery to keep dying. When you start the car it feeds off the alternator, and then starts to die.
Check your charging system, test the battery.