Hey everyone! New member here, this is my first vehicle and I really don't have much help other than myself. Was really hoping for some wisdom!

About 2 months ago when it really started getting cold, I noticed that each time I started up my 97 Blazer, it seemed like the battery got a little weaker each time. It just took a little more to start it up. Then my power locks stopped working. Finally, I went to start it and it wouldn't start up so I had to get a boost. I figured it was the cold taking it's toll. So all was fine for a few days, then bam, won't start again. Boosted. I had the battery and the alternator checked and they both passed fine.

So, few days later go to start it, no luck. Now, the battery still has juice to run the radio or lights, windows as well. But not enough to start the engine. I get a new battery and put it in, works great for a few days then the locks don't work again and sure enough today, doesn't start. It'll just kind of click until it's hooked to another battery then she runs just fine.

I removed interior light fuses just to rule anything out for what could be drawing power. But I'm really at a loss to what I should do. Any suggestions would be greatly appreciated!

Thanks so much, hopefully we can get this fixed for a young man and his first truck!

 

Wow, there is so much to check that I don't know where to begin. The first thing I would do is disconnect the battery. Be VERY careful and his rc a good way to set fire to thg vehicle. Unplug the radio fuse and if it has an aftermarket, remove the radio so the memory is not being powered. Hook a 12v lamp in circuit between the positive terminal and the battery cable. If the lamp is lit, remove the fuses one at a time until it goes out. The fuse that turns it off is the circuit drainung the battery. Be sure to unhook the negative cable again before you try to reattach the positive.

If you don't have a drain, pull the starter and have it bench tested. A failing starter can drag and need more power to crank the engine than the battery can supply.

 

Sounds to me like your alternator is bad. Where did you have it checked at? I had the alternator in my wife's car tested at advance and the chick didn't know how to read the meter and said the alternator was bad. Not believing her I investigated further myself and all that was wrong was a dirty throttle body! I cleaned it and haven't had a problem since. The point of that is I wouldn't believe the parts store folks. Easiest way to test it yourself is start the truck and disconnect the battery and see if the truck dies. If it dies you have a bad alt!

 

If u do this on a computer controlled vehicle u risk burning up the computer...

 

Huh? I've done it on probably 20-30 cars in my lifetime and never heard of burning up a computer. It will only take a few seconds for the car to die.

 

I used to make a living fixing cars that people did that to. If you have a GENERATOR equipped car, yes, this is a good diagnostic. Do it on an alternator equipped vehicle and while you may or may not blow the computer (I closed shop in '84) you do risk blowing that little diode in the alternator unit. Considering that alternators can run $100-200 for a rebuilt unit, you don't really want to do this.

There are testers today that will load test a running alternator without damaging today's delicate electronics. Since computers work on fractions of a volt on some functions, removing the battery removes the voltage spike buffer from the circuit.

In short, bad mojo, don't do it.

 

Well I nor anyone I have ever heard of has ever had a single issue with it so ill keep doing it. Sure there are testers for this but like I said I don't trust parts store employees or mechanics for that matter and I'm surely not going to buy a tool myself for something that I can do for free! To each their own I guess!