I just bought a 2000 Blazer LS 4 door, 4WD recently as a fixer upper, but have discovered that there is more fixing upping than I first imagined.

The problem at hand is that sometimes the vehicle will start normally, and at other times it will act like it has a bad battery. That would be easy enough to understand, except today when I first went out to go to Autozone, it started fine, but after driving 3 blocks to the store, when I tried starting it to leave, it wasn't simply a low battery, there was no electrical at all.

The clerk in the store checked the battery and alternator, and first said that the battery had a bad cell, but then after checking the alternator, said that it had bad diodes and might be the reason for the battery readings.

The thing that bothers me is that neither problem seems to account for it going from a normal start, to zero electrical in a matter of minutes.

I'm going to replace the alternator, but suspect that some problem will still remain. Outside of a bad connection somewhere, is there anything else that might cause this?









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Fuse link on the feed from the trigger wire on the alternator that tells it to charge.

 

Thanks. hopefully, I will better understand what you said when a repair manual that I ordered arrives. However, even if the fuse link was bad, would that account for it going from normal to dead in a matter of minutes, then back to normal after jumping it?

 

Also bad or corroded battery ends will cause all sorts of charging and starting issues.

When in doubt swap them out.

I paid $1.79 a end Saturday at Kmart and took all of 5 minutes and i have clean and good connection to my battery on my project truck so i don't have to worry about them.

 

A malfunctioning alternator would not charge the battery . If the trucks running with a malfunctioning alternator the engine would drain the battery causing it not to start

if you get a multimeter and ground it to the battery then put the pos on the alternator wire Race the truck from the cable the voltage should pickup to 14 to 15 volts maybe higher if it dose not pick up to 14 volts higher it could be a bad alternator

 

The curious thing is that the interior voltmeter does show that the voltage rises like you described, when it starts, but before starting, the same meter is supposed to show the condition of the battery instead, and that will vary from normal to weak to dead, without rhyme or reason. Of course the whether it starts, or how normally it starts, depends on the battery condition shown.

 

i agree when you turn the ignition on whats the voltage show at ?

 

As i said, it varies. I haven't paid enough attention to give a precise answer, but I think that sometimes it will show a peak at ~ 10v and at other times a low of 0v.

 

I had a very similar problem. Thinking it was a bad battery, jumped the car, went to the auto parts store to buy a new battery and while swapping out the battery we found the cable/wire that goes from +12v on the battery to the back of the alternator had a bad connection (the terminal was loose where it was crimped on the cable - AT THE ALTERNATOR). Replaced that (and not the battery) and its been good ever since.

 

That sounds exactly like my experience, except that it was the negative cable. Fortunately, I found it before buying a new battery.