Got a 2001 7.3L It wouldn't start today. Turn the key and ALL gages going crazy. Speedo and tack too. Clicking but will not turn over. Never done since new and just happened overnight. Put slow charge on both batteries. Still clicking. ( not from starter but cant see where) Could it be a sensor or fuse? If so which ones should I be checking. Thanks.

 

Weak batteries or bad cable connections usually are the cause of this. Don't forget to check the grounds too.

 

Thanks. Didn't have time to fool with this morning. Had to jump in trusty F150. Ive only had to replace passenger battery since new. May be the other one going out. Thanks for the advice.

 

On a diesel, always replace both batteries at the same time. Otherwise you'll end up with a no start condition in just a few months. My guess is you need that second battery now. Just hope the weak one didn't pull down your new battery. I'd get them both load tested sine most parts stores will do that for free.

 

I've also seen alternators do this as well

 

alternators do not have anything to do with starting. the alt. isn't switched on until about 30sec. after starting. However if the alternator has failed it will fail to charge and kill both batteries quite quickly. My guess is like the other's have suggested, that your batteries are drained from only replacing one or the terminals are corroded.

 

Ok, didn't know about both batteries. I'm a 'gas' man. Got the 250 to haul horses. Thanks yal.

 

I replaced both batteries. Cranked right up. Like I said, never really fooled with diesel's much. I figured if one battery was dead I could jump it off. NOPE!!!! Thanks for the help.