Today my Disco wouldnt start, kept trying kept trying finally gave up. went home got jumper cables, hooked it up and it fired right up! I just bought that battery!!! what is going on!? Alternator? my lights worked fine and everything, It didnt have not one symptom of a dead battery... What is going on!!! Could this cause it to just about die when i rev up the engine in park or neautral. it goes to like 1900RPMS and then shoots down to under 500Rpms and all my gauges go dim and it about dies... All because of the alternator???

 

check all of your engine grounds, battery, and take your alt. to autozone for testing... i be its a loose cable

 

Completely removed your negative battery cable from the vehicle (Don't worry, it'll take you less than 5 minutes - it's connected to the frame & a small 10mm multiground bolt just behind the battery) Bent the cable back and forth every couple inches to check for "crunchiness" or green dust falling out of the ends. If you notice either, then replace the ground cable.

If the cable ends up fine, then have the alternator tested. If it's not the ground cable, it's likely your voltage regulator is failing and you'll need a new alternator. You can check the cable in the parking lot of the auto parts store, then replace it, then have the alternator tested.

 

Maybe il just replace the ground cable no matter what and have the ALT checked too, I mean if might as well right? Thank you guys for the info, Il fix this tomorrow after work if its nice

 

I was just looking at the lights that you have on the front of your disco, how often do you run them? Lights and stereos like to kill alts...

 

your alternator is also the source of the signal of the Tachometer. If your tachometer is workin, then, the alternator is likely to be OK. That is a quick check you can do.

BR.

 

Tach works fine, Um i run my stereo with four speakers, and two 12" subwoofers... All aftermarket... Could that be killing it? when i turn my PIAAs on you can hear the car go quieter. Hmm Any suggestions? Two batteries? two Alts?

 

That is not accurate. The tach drive comes from the alternator but has nothing to do with the total voltage being made by the alternator.
Need to go get the truck started and to a parts store, have them check the voltage at 1500 plus RPM's, should be 13.6 to 14.4 volts.
By the way, do you have and fault codes?