Electrical confusion

[Stedia10]

So I replaced my alternator in my 94 Chevy K1500 4.3 Ltd V-6. I know the alternator is good, its been tested. My truck still dies if I disconnect the negative from the battery. I don't claim to be a mechanic, you guys are awesome, I just ask questions and hope I can fix the issues. Anyway, I'm really frustrated with this!!!! Can ANYONE HELP!?

[silicon212]

Well, first off, running an engine - especially one with a computer control system such as yours - without the battery hooked up and only on the alternator, can damage the alternator. You can also fry your PCM this way.

The true test of the charging system is to see what your voltage is under load. Run the engine to 1,000 RPM and turn on all your lights - your voltage should be around 13.8 +/-.5 volts.

[Stedia10]

Thanks silicon212, I'll take a look. I only unhooked the battery momentarily to see what WD happen. The is is the second alternator I've replaced. I took the first one back when it did the same thing thirty minutes earlier. This all started when I installed a car stereo.

[Stealthee]

You likely have a blown fuse in the charging system.

[Stedia10]

That makes sense. Would that fuse be with the rest in the fuse box under the dash? What WD it be labeled as?

[Tech II]

Please explain again why you are disconnecting the neg bat cable?

[Stedia10]

TechII, I I was told by several ppl that I cd check my alt by doing this?

[Stedia10]

Can SOMEONE please tell me where to find the alternator fuse for my 94 K1500 4.3 v6?

[aleekat]

Originally Posted by Stedia10

TechII, I I was told by several ppl that I cd check my alt by doing this?

That's how old mechanics used to check cars with generators. Not with alternators. Get yourself a voltmeter. You can find them pretty reasonable for charging issues. As far as the fuse. Most fuse covers have labels for what they go to. Either inside the car or under the hood. Did you disconnect the battery when you installed the new stereo?


http://www.aa1car.com/library/charging_checks.htm

[Tech II]

The fuse is usually a fuseable link, located on the starter......

As Aleekatsaid, check output with a voltmeter.......

Engine not running, 12.6 volts.....

Running, 13.5+ volts.....

Turn on headlights, rear defogger, blower on high.....voltage could drop to 12 volts or even more, depending on charge in the battery......now rev engine to 2000 rpms, and voltage should go up to at least 13.0 volts....

[Stedia10]

So, long story short. I replaced my battery, (needed one anyway), replaced my alternator, the battery light came on. Checked all connections, found that me positive side mount bolt was stripped. Gonna get a new one today. I have a voltmeter, not to sound COMPLETELY dumb but exactly how do I use it to check this stuff? What settings? Also, I've discovered that, being a W/T, I have no under hood fusebox. There is however, a junction box located on the passenger side fire wall. I'm learning as I go, so any pointers wd be extremely appreciated! Thanks guys!

[Stedia10]

By the way, I did not unhook the battery when I installed the stereo.

[Tech II]

Just turn your voltmeter selector switch to DC volts........black lead is installed in the ground(common) port....red lead, into the bat port(the holes are usually color coded to the leads).......now red lead to pos term of battery, and black lead to neg terminal of battery.......this is where you will get the readings for the previous mentioned tests......

Even though that bolt was stripped, it started the vehicle......which makes me wonder about the fuesable link......

With voltmeter on, attach leads to pos and neg bat terminals......should read 12.6 volts(fully charged bat), with car not running and nothing on.....now move the red lead to the big red wire connection on the back of the alternator(if there is a rubber boot there just move it for the connection).....black lead remains on neg bat terminal......should read the same as the battery....if it doesn't, if means that fuseable link is open, and the alternator is not charging....

[Stedia10]

Tech II, Dude that's awesome!!! So my battery reads 12.6 just like you described but the alternator reads 0.8 - 1.2. Now then, if this is the case, then what do I do about this " fuseable link"?

[Tech II]

Check the fuseable link.....If the connections are ok, chances are it is blown...replace it...