1997 Blazer battery dying

Check the gauges fuse no.4 10amp in the I/P fuse block if okay double check the wiring to and from the alternator and the battery

Use an inexpensive digital voltmeter to measure battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, replace the generator. It's possible it is failing intermittently and it was tested while it was working.

It is real common to go through four to six of these piles in the life of the vehicle. Many professionals are finding out that to reduce the repeat failures, you must replace the perfectly good battery at the same time. They will work fine in pre-1987 vehicles, but as they age, they lose their ability to absorb the huge voltage spikes these generators produce. Those spikes can wreak havoc on sensor signals for all of the computers on the truck as well as damage the internal voltage regulator.

Caradiodoc

I wouldn't be too hard on the first guy. You had an intermittent problem and he may have run the test while the problem wasn't acting up. He should be commended for not trying to sell you something it appeared you didn't need. The second guy might have not been aware this was intermittent and he could have just used the first guy's testing methods as an excuse or as small talk.

Intermittent problems are always frustrating whether it be in car repair, tv repair, or a computer problem. You never know if it is solved if it doesn't act up again. You can only know it was NOT solved if the problem does show up again.

Caradiodoc