vloney Posted December 8, 2011 Share Posted December 8, 2011 I put an alternator on an 04 f150 5.4. Uneventful, charging ok. Customer comes back next day complaining of a noise that wasn't there before I did my work. I went out with the customer to listen to the noise, it was the "singing" that an alternator makes when charging. I told the customer that it was normal. "Well that aint right, it shouldn't be making that noise". "Sir, thats the noise one makes normally when it charges". "Why didn't the old one make that noise?" "The old one wasnt charging". "Well I want a new one!" I told my SM about it, suggesting he listen to the noise. "I dont need to, just replace the alternator!" So after replacing the alt, SUPRISE! The noise is still there. After several heated exchanges with my SM, HES GETTING A TECH ASSIST! If it wasn't so funny, I'd be offended! Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted December 8, 2011 Share Posted December 8, 2011 I'm assuming the vehicle came in for a no-charge condition, in which case the battery will probably be low on charge. Did you put the battery charger on it while you were installing the alt? If the bat is super low the alt will be working its ass off to fill up the battery. I'd check the charge rate at the battery, it should spike up to 70-150 amps just after starting but settle down under 10 amps within a minute or so. If the battery is shorted it could stay excessively high, which could cause diode noise from the alt and short alt life. A really healthy and happy battery will settle down to about 2-3 amps within a minute of starting the engine. Quote Link to comment Share on other sites More sharing options...
vloney Posted December 8, 2011 Author Share Posted December 8, 2011 Yeah, battery charge and everything. The noise is barely audible. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted December 8, 2011 Share Posted December 8, 2011 Several different brands of rebuilt alternators contain a warning "THIS IS NOT A BATTERY CHARGER" and some of these manufacturers will not honour their warranty if they suspect that a unit has been installed and allowed to charge a dead battery. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted December 8, 2011 Share Posted December 8, 2011 And when you see the paint on the stator turned black you know the story.... Quote Link to comment Share on other sites More sharing options...
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