1998 4.6 106,000 Supercrew Auto 2wd.

Had head gasket and bolts replaced in September along with water pump, thermostat and radiator. Battery doesn't hold its charge and runs down after 6-7 short trips. Have charger so not a massive problem at the minute. However, when accelerating when the engine is cold, the battery light comes on. Fades in and out and when revs are high, warning light is strongest. Nothing at all when engine is warm.

I am thinking that the alternator isn't working properly but have checked the current between the points when running and she's over 12 volts so.....

Anyone got any ideas?

Cheers
Damo

 

I seem to remember a thread somewhere yesterday about the very same topic, so please try a search next time.

Anyway, it seems like its common on these trucks to have the battery light come on under heavy acceleration if the alternator is failing. I would replace the alternator if I were you, because if the battery isn't staying topped off then its obvious that its not charging properly. Also, above 12 volts at idle doesn't mean anything about the alternators condition. Actually, it should be much higher than 12. Mine idles at 14.4 volts I believe.

- Erik

 

Well before you start throwing parts at it this is what I would do to rule things out. Have napa or another auto store to load test battery. Check battery connections for corrosion dirt ect. Check alternator connections make sure they are tight and clean. Make sure the part of the case and the alternator bolts are clean and the parts of the engine block the contact is also clean. With engine running and somebody reving it to 2 grand use a voltmeter to check between ground cable(battery side) and ground cable(alternator side). Do the same thing for the positive cable. There should be no more then .2v difference if there is then cables have to high of resistance and need to be cleaned or replaced. If all this checks out then I would bet it is your alternator.

 

sounds like alternator on last legs

 

I would replace it soon mine did the same thing and didn't think anything of it until it quit going down the road. Boy was that fun.

 

It's the alternator. I'm the one that posted in the other thread.