I have a 2000 Blazer LT 4x4 4.3 with 106K on it.

My problem is I think I have may have a short and where should I start looking.

My gage inside the Bazer has been latey showing on the discharge side ( A little to the left of the 14 which is straight up) It use to run a little to right as the vech was running with the air on etc and I expected that.

But now its discharging. I check the battery 14.3 and the Alt 14.8 votes while running. I had this double check up at autozone with a guy who was pretty savy (For a change). When he 1st tested it he said my battery was only at 55% charge and for a good test it should be at least 70%. But in the mean time he did check everything and it all appears to be good, battery, Alt and votage reg. But, I went home put it on the charger and when it was charge I took it back to over there ( I live about a mile from there ).
When I got there (Nothing running, no a/c, radio etc). My battery had already drop to 85% in one mile, but yet everything checks out.
He said I must have a short or a ground problem some where and happy hunting...For the battery, Alt, and votage reg show all good and he let me see the meter to show me and he was correct.
I tried wiggling the ign switch to see if that was bad, it appears to be good plus I don't have any of tell tail lights coming on the dash that would lead that way. I just had the fuel pump replaced ($729.00 bucks worth), I had at first thought maybe since the pump was going bad it also might be shorten out. That wasn't it.

So here I sit with my finger up my butt going Duh and scrathing my head as to where to start in the search for the problem.

Can I get a starting point from anyone? And how to do it. Remember the bat, alt, vot reg all check out and I don't see a ign switch problem (Could be wrong there). But what would drain the Bat that fast? Starter? it starts just fine, no noise what so ever, maybe a wire hitting something down there?

Any help would be deeply appreciated.

 

start doing voltage drops on your cables. bat-starter-alt-fuse panel under hood. check both grounds and positives both while cranking and running. want to be in the range of .1-.3vanything over .5v and replace the cable. clean up grounds and any connections as you go as well

 

Thanks will do. I have also notice something else. There is no big battery drain when the vech is turn off. (except for the norm, clock running, security, etc) It only appears when the vech is running.

 

one more thing to check. get a volt meter put it on acv, with the truck running put the positive lead on the alt output and the ground lead on the case of the alt. you want no more the .5v ac. if you do than replace the alternator because the diode bridge is leaking.

 

Going out there right now, its only 105 in garage..nice cool day..hahahahahahaha Will let you know what happens.

 

Lets start like this a short you would be blowing fuses. To check for a draw one of the best instructions http://www.wikihow.com/Find-a-Parasitic-Battery-Drain.

Now did he check for a sulfated battery at the shop by doing this http://www.aa1car.com/library/2003/us20310.htm. it is called the 3 minute charge test in some places.

At 14.3 to 14.8 volts usually 14.2 is what your looking for. Anything above 15v is going to overcharge your battery and cause it to become sulfated.

I agree with the diode or rectifier bridge testing, do you see the bat light on very dim by any chance.

 

Thanks all for your reply's. Question about Battery Light, I have a volt meter no idiots lights and it stays on the minus side of 14v and if I turn the a/c it gets a little worse and after I drive it lets say 5 miles and put it on the charger for the 12 volt deep charge it takes around 1 hour to charge, if I put it on the normal 12v charge it takes about 20 minutes, in either case driving 5 miles should not cause that much of a draw down. Now with that being said; While my vote meter in the vechile shows on the minus side of 14v when I check the batter while running and the Alternator, Battery now reads about 14.3 and the Alt around the same maybe a tick higher. Now just for ****s and giggles yesterday while the vech was running I put the charger on it and was CHARGING at around 7 amps, now this is after a full charge. That doesn't make good sense..But I have notice that the light under the hood stays on a lot longer then it use to, now about 1/2 hour where before maybe 15 mins and if you bump the bulb it will come on again. Also when being charge under the 12v deep cycle it will hang there around 4amps until the under the hood light goes off the charger will say complete charge.. Also notice when I took a reading with the charger on and the engine running both the batter and Alternator will read around 31.3 volts now thats some charge!

I have come to this conclusion so far, since the Alternator has a life time warranty I'm going to take it off and exchange it, it not that hard and I'm tiring of Pi****** around looking, then if that don't work I will take it do my mech and tell him to have at it.

I would also like to add this: When I 1st took it up to autozone the guy said for a good test the battery should be at 70% charge, when he check it, it was at 55% and I said what! I haven't went no where except to the store and back a time or two. He went ahead and check everything and he said it all look fine and for me to go home charge it up and come straight back there and he would test it again. Since I only live about a mile away I said sure, charge it up using the 12v deep cycle and headed back with noting on and the battery read 85% charge, now that got me. One mile and 15% loss, Na something wrong and it apprears to be drawing down ONLY when the car is running. I can fine no draw down except the under the hood light staying on longer then it use to.
And when I put a turn signal on I can see the vote meter in the vech move back and forth as the turn sig blinks, to me thats Alternator.

So, my cure is this Life Time Warranty swap it out and go from there..

 

I would also like to add No blown fuses...

 

Well, I made the swap out and had to clean the neg battery cable (Side mounted so its hard to see whats going on underneath) and things got better but not the cure. The neddle pretty much stays top dead center until I turn the A/C on then its drops to the neg side by a point of two and when you hit the turn signals the meter goes back and forth. So I'm pretty sure its a short now and I really don't have the patience (sp) to do it, so I'll take to my Mech. Plus its going to be around 105, 107 this week and I can't hang out there to long, some of the drugs I take from the VA says to stay out of direct sun light for to long...hahahahahaha..try that around here...

However you can hear the Alternator whiring so its charging and I'm getting around 14.5 at both the Battery and Alt now that leave little to no room for a charge so something is drainning it only while running. To me and my 2 cents I thinks it might be the starter that draws a lot juice and was really use when the old fuel pump was taking a dive on me or maybe the A/C, The compressor sounds like there is a bucket of bolts running around in it (Been that way since 2002 when I had it change out and sounded like that before I had it change out). I'll let the pro's figure it out, thats why I'm only a "Back Yard Mech" know a little but not enough when it comes to elec except back in the good old days where there wasn't much to it or and old Harley where there is only 3 main wires.