electrical issues

[Hambeezie]

I have a 95 Chevy c1500 (Cheyane with 4.3L paired with the 4L60E) that I just bought for $200.

It needed a new alternator, battery and wire connecting the alternator to the battery. I replaced all 3 of these, and it still is not charging the battery. A fully charged battery can go for a 5 mile drive, and then fail to start the truck for the drive back.

The battery tests at 12.6 volts, and the alternator tests that it is charging. With jumper cables connected the truck starts no problem.

The other issue is that I can start the truck without the key. I installed a new ignition lock cylinder and the problem persists.

Even without the new key in the new ignition switch it will turn.

Some circuits that are supposed to be off with the ignition turned off remain on (most notably the light on the gear indicator on the instrument cluster)

 

I am at my wit's end and can't figure this out. Everything I know about trucks yells me it should be charging,

[davester]

what is the voltage at the battery when the engine is running?

maybe there's a wiring problem, so the alternator can't deliver much current to the alternator (either via the power or ground connection)?

[xcursion88]

Battery connections tight? I don't doubt your mechanical prowess but many people think their terminals are tight yet I can grip it and twist it. 

 

Alternator connection good?  

 

How do you know it's charging properly? 

 

I see many alternators thought to be good but in reality they aren't.  

 

Watch the alternator readout with a full load on it.  Lights, radio, AC compressor on... (defrost) 

 

Now check it after idling like that for ten minutes and see if it drops. 

 

There are bad alternators that will be OK at initial startup but once run a bit the charging continues to decline. Then after 10 or 15 minutes the output is barely 12 volts. 

 

Can the truck only go for 5 miles and then it dies? 

 

Or are you saying if you go 5 miles and shut it off you can't get it to start back up. 

 

Can you get in truck and drive it for hours? If so that eliminates the alternator. 

 

Go back to the simple things. 

Check your connections at the battery positive  and alternator... (checking tightness and quality of the terminal / connection. 

Also check your negative at the battery and the ground side of that cable at the engine.