early 99 f350 7.3 4x4 after recieving jump from AAA (ford f-250) thank god.
readout indicated no charge from alternator...replace alternator (duralast gold) same problem...find ring terminal connection to alternator split...replace, fires up and seems to charge up...went to Les Scwab hav ignition system check says alternator not charging...(but it is)...park after driving for 2 days batteries dead...batteries checked...they r good recharge(Interstate MTP-65's)..they immeadiatley drain and truck dies...have i some how broken the 2 wires to plug in to alternator...they look good...Is there some type of relay in the system i am unaware of? Any and all help would be much appreciated.
Thank u in advance

 

Check to see if both big terminals on the glow plug relay are hot. One should be and one should not be when the truck is turned off. Same for Air intake heater relay. Either would cause all your problems.

The only other thing I have heard of is was a fusible link blowing and causing a battery light to stay on all the time, even with new alternator. You did not say that so I did not mention it at first.

 

Perhaps this will help.

 

if the fusable link for the charging circuit is bad, the alternator will show output and test good, but the batteries will not see the charge.
also if the diodes in the alternator are bad, the batteries will discharge overnight.
the alternator will test good even if the diodes are bad, because they stores check for output, not diode condition
to test for bad diodes, feel the alternator on a cold engine. if it is warm, the alternator needs replacing. .

 

thanks guys...ill report back, can't get to her till Monday

 

ok Monday came early...both sides of glow plug relay are cold...I did AIH delete years ago...charged all night...batteries read 12 v running and shut off...no lights on dash staying on....so test before and after fusible link??

 

before and after. should be 12 volts on both sides with key on engine off.

 

second alternator first one bad now truck still does not show output from alternator, and battery light will not shut off on dash...have checked every fuse and relay...where and what exactly are you referring to as fusible link???

 

The Sensing & Switching Circuit controls the Alternator Output (on/off). Fuse #6 in the under hood junction box (5 Amp). connects the circuit to the instrument cluster.

Check for continuity from Fuse #7 (LG/R) to the Alternator Plug. If there is no continuity, I have found several:

Chafed wires at the valve cover plug.

Corrosion on the bottom of the Junction Box

And defective Pins on the Alternator Plug.


Hope this helps.

Tom

 

it was Fuse #6 under hood, looked good but failed test...alternator putting out 14.40 v.....THANK YOU....the original alternator had some plastic piece break inside causing short...but was very frustrating buying new alternator from Autozone Duralast Gold supposedly triple tested...was bad.
bought lifetime alternator from Napa...guy looked at me weird when i had him test before i left store....Thanx for all the help!

 

Good deal.

 

That was a very good idea!

Stuff happens........

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