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'97 7.3, Charging problems

3K views 8 replies 5 participants last post by  gbear 
#1 ·
Yesterday my battery light came on and the voltmeter is showing about 9 volts. I took the truck to NAPA, they tested alternator in the truck and said it is not charging. I brought the alternator back to test out of the truck and buy a new one, it tested OK. The parts guy said I don't need an alternator.

I took it to AutoZone, they tested the batteries out of the truck and both tested bad. I bought new batteries, but still have the red battery light on the dash and still charging at just 9 volts.

Do you think the Alt is bad? It tested good once so I don't want to spend $170 if it wont fix the problem. What else can I try on my own?

thanks in advance for your advice
 
#3 ·
Yeppers, sounds like alt. The bad batts. probably had something to do with it going bad. I have been told it can be a chain reaction, if one battery goes bad it causes the other to go, and all of it is hard on the alternator.
 
#4 ·
I would suggest that you charge the new batteries really well before putting the new alternator in service. Low batteries can fry a new alternator.

Jim
 
#6 ·
It depends on how powerful your charger is. I would just charge them individually. I will take a little longer but you won't overload your charger.

Jim
 
#7 ·
If it checked good at NAPA I'll bet its bad !! One of the dieods has gone out so its putting out AC but cant convert it to DC so no charge for batts. Ive seen this a lot of times, there are 4 of those little critters in it an if you lose 1 it will check good but cant supply a full 13 to 14 volts under load... And yes to the chain reaction thingie that is mostlikley that cause a diode to shoot crap...... Bill
 
#9 ·
Great I'm glad you got her up and running

Jim
 
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