The other day I was driving down the road and all of a sudden my lights started dimming in an out, after a minute or so my gadges started going crazy and the engine started cutting in an out, it ultimatly broke down and I lost all power.

The power tested good for a few minutes after getting a jump, a steady 14v was read on the meter. However it died shortly after rolling down the offramp of the freeway. I decided to replace both the altenator and the battery for the sake of it.

After replacing the altenator I drove it around a parking lot for a couple of minutes and it seemed fine, however the problem came back once I hit about 25mph. I managed to limp it to a friends house that was near by.

Keeping it at slightly over 1k rp's and cruizing about 25mph it seems to stay stable most of the time. Going over that limit it's hit or miss, the gadges start going nuts and the battery starts reading around 9 volts, everything goes dim and the engine starts cutting out again.

Any ideas?

 

It sounds as though one of your main battery cables has gone bad. Most likely it is the main negative ground.

I had a similar issue as you described with my own 01 blazer. Mine was a bad Neg cable but it could just as easily be the positive cable.

 

So it turns out that a while back I had a bad check valve, which melted the entire AIR system, which I didn't notice a wire harness that also got melted by it. I guess the cold and the snow possibly exposed it enough to start causing shorts.

I wonder if anyone has written a damage prevention guide of sorts for this model blazer. It just seems to have a lot of poor designs. Had the wire harness been moved against the firewall(where I'm moving it now), a couple inches from the hot lines this never would've happened. Not to mention I'm not so thrilled with the AIR system in general I would like to remove it if it's still possible to pass inspections without it or with a modified version of it.

 

I have a very similar problem on my 97 blazer..But mine is even more predictable. At 4000 RPM battery voltage drops and lights dim. Once RPM drops the altenator picks back up. Another thing I notice is that the fuel gauge climbs and occasionally pegs on the full side when the voltage is dropping. Im suspecting a poor ground connection. I had the altenator check on the vehicle. It shows good until you increase the RPM over 4000 RPM then it shows low voltage/bad regulator. I have been studying the wiring diagram and noticed that the altenator is basically turned on by the vehicle control module. (Which coincidently also controls the fuel gauge.) It just seems odd that 4000 seems to be the magic number. Ideas?