charging system woes

vegas39

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After fighting half the day with alternators and regulators on my 89, it got dark and I was tired and accidentally shorted the wire that goes from the alternator to the relay on the fender. The fusible link burned away, so I went to autozone and they sold me a new 14 gauge link, its the biggest they had. The wire from the alternator appears to only be 10 gauge and from what I'm reading, 14 should be fine for the link but when I got everything back together tonight, the wire gets really hot.
The fusible link gets really hot and so does the connector where I crimped the wire from the alternator and the wire from the regulator, to the fusible link.
This is a 70 amp alternator.
By the way, my battery light came on this morning and the volt gauge was reading low, so thats what prompted me to change my alternator in the first place.
 

reklund

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I haven't forgotten about topping up your AC...so we can fix that wiring at the same time. Either run two pieces of fusible link in parallel or build a new harness with a maxi fuse in line.
 

icanfixall

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Thats a possibility Ken. Just take it back and have it checked out for burned diodes in the bridge. Its a bit of a job but you can buy a diode bridge and change it out your self too.
 

vegas39

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I think you blew the diodes in the new alternator.

This happened before I took it in to have it tested and they said it was ok. I dont understand how a little fusible link can stay cool enough when it carries a big load, such as headlights, a/c etc.
Even the wire from the alternator is only 10 gauge, just doesnt seem like enough for a 70 amp unit but thats how it came from the factory.
 

vegas39

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Dont ever buy an alternator from Oreylies, or however its spelled. I bought one for my 89 there last year and it died yesterday. When I bought the first one, they had to change the pulley to a double and they also had to re clock the unit.
When I went in yesterday for the free replacement, he changed over the pulley but didnt know how to re clock the alternator. I asked him if he had an exact replacement and he said no, thats how they all come and when he tried to re clock it for me, he broke it.
He ended up refunding my money and I ran over to Autozone and bought a unit that was already clocked properly and already had the double pulley installed.
 

OLDBULL8

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Vegas; You do know and if you don't, an Alternator is NOT made to charge dead batteries, a battery is considered dead when the voltage is 10.5 VDC or below. A 70 Amp Alternator will charge it's full output at about 2000 RPM, but only for about a minute, like right after a start. All the current (AMPS) come from the battery for whatever you have turned ON, the Alternator only tries to replace the current your taking out of the batteries. Putting it this way, when the engine is OFF, and you have a bad battery, that bad battery will suck the voltage/current out of the good battery until the voltage is equal in both.
Battery/Alternator lesson 101.
 

icanfixall

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Kenny what Bill has posted is correct. An alternator is asked to do more work than its designed for. Al its supposed to do is refill the battery after a start. Then when thats done it feeds power to any electrical device thats calling for power. The battery does not cause our engines to run. Its there to start it and backup the alternator if it goes bad. BTW all we need to keep our idi running is about 7 volts supplied from a battery to the fuel shutoff solenoid. As long as its getting power we can run till something else breaks or runs out of coolant, fuel or oil. Hope this helps you and others to understand this mystery alternator thingy. It will recharge a dead battery but it sure works hard doing it. That hard work sometimes opens up the smoke canister too...:eek::angel::D
 

vegas39

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Vegas; You do know and if you don't, an Alternator is NOT made to charge dead batteries, a battery is considered dead when the voltage is 10.5 VDC or below. A 70 Amp Alternator will charge it's full output at about 2000 RPM, but only for about a minute, like right after a start. All the current (AMPS) come from the battery for whatever you have turned ON, the Alternator only tries to replace the current your taking out of the batteries. Putting it this way, when the engine is OFF, and you have a bad battery, that bad battery will suck the voltage/current out of the good battery until the voltage is equal in both.
Battery/Alternator lesson 101.

I wondered about that last night and knew they were a little low but they still had plenty of oomph.
I have seen the problem you are referring to with my motorhome once when one of the batteries went bad and was feeding off the other one.
I probably should make sure I dont have a bad one.
 

icanfixall

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When we have a bad battery the system gets pulled down to the lowest battery charge. Think about the 2 batteries as 2 tanks and they are connected together with a hose. If one of them drops down the level then the other full tank will refill the low tank till they are both level. Same thing with a full or half full battery.
 
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