Possible alternator problem

507 Views 7 Replies 3 Participants Last post by ghart, Aug 19, 2008

blackhawk

Discussion Starter · Aug 17, 2008

Running at cruise (3000-3500 rpm) I have 13.5-14 volts on my gauge. Running wide open it drops down to 12.

I am going to see if it also does it on my second battery.

A couple weeks ago I blew a power steering belt at WFO and I lost power and my gauges went haywire for a second. The alternator belt goes around the water pump only. The power steering belt goes around the crank, water pump and steering pump. So, when the belt blew my alternator quit spinning.

I was thinking that a piece of the belt may have smacked the alternator and knocked something loose. Or maybe it stopped abruptly when the belt blew?

I just don't get why it seems to be working at lower rpms but not at high rpms.

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Fyhr Factor

· #2 · Aug 17, 2008

I think your alternator is fried,
The gauge might be just reading the battery voltage, not the alternator output, so the higher rpms suck more juice and drop the voltage down..

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blackhawk

Discussion Starter · #3 · Aug 17, 2008

I charged the battery for about 2 hours before I went out today. At cruise still 14 volts. Pinned it and it dropped down to 12 again and then after 1-2 seconds popped back up to 14 and stayed there.

Tried it 3 times and same thing every time. At least it's coming back up now but I'm still confused as to why it's doing this. I thought maybe the belt was slipping but there is no smell, noise or smoke.

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blackhawk

Discussion Starter · #4 · Aug 17, 2008

Fyhr Factor said:
I think your alternator is fried,
The gauge might be just reading the battery voltage, not the alternator output, so the higher rpms suck more juice and drop the voltage down..

You may be right but everytime I've had an alternator die it just quit. I've never had one work except for WFO rpm. Weird.

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Fyhr Factor

· #5 · Aug 17, 2008

Yea, I know it's strange, but had one do that on my old boat too.. guess it depends on what got fried in there..

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Fyhr Factor

· #6 · Aug 18, 2008

I was just thinking this morning, I forgot to mention to you to check & clean all the power connections and grounds on alternator & battery... any corrosion on any terminal can do some weird stuff too..

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blackhawk

Discussion Starter · #7 · Aug 18, 2008

Fyhr Factor said:
I was just thinking this morning, I forgot to mention to you to check & clean all the power connections and grounds on alternator & battery... any corrosion on any terminal can do some weird stuff too..

Thanks I did do that yesterday. I was so happy that the volts were coming back up yesterday I forgot to switch batteries to see if it still dropped with battery #2.

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ghart

· #8 · Aug 19, 2008

I've seen this happen in the past. The slip rings are probably just glazed. Just pull the alternator apart and clean them up with some emery paper.

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