95 Blazer, won't accept jumpstart, no dome light, smoked wires

[shemp01]

My 95 Blazer was running fine, got to parking lot after work and the battery was totally dead. I didn't leave anything on, so that was strange. Hooked up jumpers cables using coworkers car, using correct polarity of course, and no radio or dome lights come on and no cranking - NOTHING. Waited for my wife to pick me up and try again to jump. Same symptoms. Had her rev the engine a bit and before I could get in to try cranking it noticed smoke by the battery! Disconnected the leads real quick and saw that it was insulation smoking on a single wire off the positive terminal heading over towards the alternator. Couldn't tell if it does go directly to the alternator. The wire was hot of course as were the jumper cables due to the high current flow.

The battery is the best one you can get at Autozone, not too old, it could use a bit more water, but nothing extreme.

Could there have been a sudden failure of some component in the alternator/regulator after I turned off the car in the morning, causing a short, draining the battery and then causing the jumper cables to just short through my truck? Again, no dome light or nothing when trying to jump. Never seen it before.

I have replaced the alternator once like 7 years ago w/ an Autozone one.

What can I do to troubleshoot besdies taking the battery and alternator to Autozone or whereever for a free test?

Or is it something else?

[Gabe25]

First of all try checking to see if your battery connections are good and tight and corrosion free. With a Volt/Ohm meter. Test the Battery cable for continuity from the Pos. side to the alternator and from the Neg side to the engine ground. It sound like you mite have a broken battery cable. Let us know what you find.

[shemp01]

Gabe25,

Thanks for the reply. I'll check it after work. I don't think I have an open ground since the circuit (running car to jumper cables and back) was clearly carrying lots of current since it smoked a wire. Seems like the wire that was smoking or whatever it is connected to is shorted to ground. I guess it could also be worn through insulation and not broken, but touching the block at that point and giving a short circuit. Given that, I need to check for continuity from the positive terminal to ground also - which it should be open but seems like it isn't from my problems.

Anyone else have ideas?

What if neg terminal to ground is good and positive terminal to alternator is good and positive terminal to ground is open (as all should be on a working vehicle)?

[Gabe25]

Originally Posted by shemp01

Gabe25,

Thanks for the reply. I'll check it after work. I don't think I have an open ground since the circuit (running car to jumper cables and back) was clearly carrying lots of current since it smoked a wire. Seems like the wire that was smoking or whatever it is connected to is shorted to ground. I guess it could also be worn through insulation and not broken, but touching the block at that point and giving a short circuit. Given that, I need to check for continuity from the positive terminal to ground also - which it should be open but seems like it isn't from my problems.

Anyone else have ideas?

What if neg terminal to ground is good and positive terminal to alternator is good and positive terminal to ground is open (as all should be on a working vehicle)?

Being that it smoked the wire. It would be safe to say that you have a short somewhere. Like I said early. Check both POS & NEG battery cables for continuity and any type of break in the insulation. More that likely you'll find a break in the POS Cable that's shortin out your electrical system. If so, replace cable and make sure that you check all your fuses. Some of them mite of blown to safe you for more electrical damge.

[shemp01]

So, took battery and alternator, and they both checked out fine at Autozone (after they charged my battery). My positive cable was pretty corroded, although not horrible, but I bought a replacement end anyway since one of the wires was a bit fried (from the smoked insulation). Hooked it all up and it started great. I assumed that perhaps a high resistance connection to the positive terminal caused heating and that was what smoked the wire. Of course it was strange that it all failed so suddenly....

This morning the truck was totally dead again!

So I must have a parasitic draw (something draining the battery).

Is the best way to test for this to take the ground cable off the battery and start using a test bulb between a fuse and the neg terminal and go through all the fuses?

I assume even with a totally dead battery that it should now jumpstart fine right? Don't want to smoke any wires again....

[shemp01]

Found this on "wiki-how", of course I'll need to charge my battery to do this:

Remove the negative side battery cable from the negative battery terminal.

Attach an ammeter(this measures amperage) between the negative cable and the negative battery post. wait a few seconds to several minutes for the car to go into sleep mode. i.e. when you make the contact with the test light the cars computer systems "wake up" after a bit of time they will go to "sleep".

If the ammeter is reading over 25-50 milliamps, something is using too much battery power.

Go to the fuse panel(s) and remove fuses, one at a time. Pull the main fuses (higher amp ratings)last.

Watch for the ammeter to drop to acceptable drain. The fuse that reduces the drain is the draw. Consult the owners' manual or service manual to find what circuits are on that fuse.

Check each device (circuit) on that fuse. Stop each lamp, heater, etc. to find the drain.

Repeat steps 1&2 to test your repair. The ammeter will tell you exact numbers.

EDITERS NOTE: The original author listed this repair using a 12v test light. As an ASE certified mechanic, the best place for your test light is the trash. A test light doesnt measure voltage; it shows if enough voltage is present to light the lamp.

An ammeter meaures current (in amps), and that is what you are fighting against if you have a parasitic drain problem.

[Gabe25]

Originally Posted by shemp01

Found this on "wiki-how", of course I'll need to charge my battery to do this:

Remove the negative side battery cable from the negative battery terminal.

Attach an ammeter(this measures amperage) between the negative cable and the negative battery post. wait a few seconds to several minutes for the car to go into sleep mode. i.e. when you make the contact with the test light the cars computer systems "wake up" after a bit of time they will go to "sleep".

If the ammeter is reading over 25-50 milliamps, something is using too much battery power.

Go to the fuse panel(s) and remove fuses, one at a time. Pull the main fuses (higher amp ratings)last.

Watch for the ammeter to drop to acceptable drain. The fuse that reduces the drain is the draw. Consult the owners' manual or service manual to find what circuits are on that fuse.

Check each device (circuit) on that fuse. Stop each lamp, heater, etc. to find the drain.

Repeat steps 1&2 to test your repair. The ammeter will tell you exact numbers.

EDITERS NOTE: The original author listed this repair using a 12v test light. As an ASE certified mechanic, the best place for your test light is the trash. A test light doesnt measure voltage; it shows if enough voltage is present to light the lamp.

An ammeter meaures current (in amps), and that is what you are fighting against if you have a parasitic drain problem.

That will work. Good luck and keep us posted.

[shemp01]

So I'm a moron. This last time the dome light was on and that drained it. It was interesting to see that the dome light was using 3 amps though...

Now the drain is 37mA and all is fine.

I am still wondering why the initial jumpstart didn't work and smoked wires. I suppose my positive cables near the battery were so resistive that it heated up and smoked the insulation on the nearest small wires???

Thanks for the help.

[Gabe25]

Good to hear that you got your truck back on the road. Thanks for leting us know what you found.