1999 F250 SD 6.8l gasser. Amp meter (dash) is all over the place. Alternator, starter and solenoid are all new. Did not correct! Alternator puts out less that 12.2 amps unless I turn on the bright beam on the headlamps. Then it will charge at 14+. Also, there seems to be a drain on the battery at all times. Battery will need charging every two days. Once smelled what could have been burning wires. If true, came from under the dash. Do have mice around and am wondering if I have a hungry rodent problem however I cannot find any evidence of damaged wires. Have looked hard but have not removed the dash. Have a broken windshield that seem to be allowing water to run down the inside of the firewall onto the driver's side floor. Am pretty good at fixing stuff on my trucks but this is kicking my butt. Thoughts?? Also, the truck (sometimes) wants to start without me in it and with the keys in my pocket.

 

possible bad ground cable, or ground connections... frame to body.. wiring to body.
connections between Engine and Frame ..


bad positive battery cable..


and just looking at cable may not reveal true condition.

 

Your dash gauge should be reading volts not amps. KOEO volts should be apprx. 12.5 volts, running volts should be at least 13.5, preferably more, like 13.9-14.4. If you have a multi meter measure right at the battery, if battery volts (running) is low check directly at the output stud on the alternator, if it is still low you most likely have a bad alternator, if it is closer to 14.0 -14.4 volts then you have a wiring issue.

 

also, check that the belt running the alternator is clean [on the inside] and adequately tight. Once I had an alternator replaced, but it wasn't adjusted properly so the belt wasn't tight enough, and it didn't squeal, but it also couldn't charge the battery and the alt. light didn't come on... less of a problem now with the spring-tensioners...

 

Electricity obeys simple rules, but when mice eat the wires, well... The rules don't always apply.

As to the charging issue, all I know to tell you is learn what the alternator needs to work and look to see if it's got it. What else can you do?

 

Thanks for the responses. As indicated, the alternator is a new NAPA rebuilt. Checked output this morn' and it is putting out 10.33 volts. Check its ground and it is. Belt tension is fine. Grounds from frame to body and battery to block are fine. Ground from battery negative to body (by battery) are fine. Bad rebuilt alternator? Or voltage regulator??

 

have alternator tested..replaced.

 

If you are only getting 10.33 volts out you have a bad alt. the regulator is built in. Have a shop test it off the truck, or see if NAPA will just replace it for you.

 

Either bad alt or wiring to it. Alt light has to be working. fusable links have to be good.