Here is the deal, this has happened once before, and now i dont think that my truck will snap out of it. So when i start it, the batter light comes on, and my meter only shows at the bottom of the normal range, the battery light will come on and off but the needle will not move. this happened the other day when i had to get to work and after work it was just fine. now today i went to start it and when i went to leave and put it in gear the truck just bogged down and tried to kill itself, is this a bad alternator or possible the regulator maybe? I must point out im at school with just my small tool box and limited common tools. im going to take the alternator out tomorrow after class and run it to get tested, any thoughts?

 

Does the truck crank over slowly?
Are the headlights dim?
Is there any other indication that the truck is not charging?
What engine do you have in your truck?

IME, most parts stores don't know how to test an alternator properly.
Can you borrow a voltmeter?
Check the voltage at the battery with the engine off and with the engine running.

You should have around 12.5V at rest and 13.5-14.5V with the alternator turning.

In that vintage you likely have a 2G (second generation) alternator with integral regulator.
If so, there will be one screw on the back that says "ground here to test"
You can do this with a paperclip or any small stiff piece of wire.



By grounding the 'F' (field) screw to the case you should cause the alternator to give its full output.
WARNING! only do this momentarily. Just long enough to see how -or if- the voltmeter reacts.

If you do have a 2G alternator and have charging or overnight battery drain problems the FIRST thing to do is replace the charging plug pigtail.
This is the square plug with two 10Ga black/orange wires and one white/black.

This plug was notorious for corroding internally and melting down or causing fires.
There is a Technical Service Bulletin -#96214- on the problem and it is recommended to replace it any time the battery or charging system is serviced.
The pigtail is available for under $10 at almost any parts store.


Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman/Motormite #85123 / 08622
etc.....

 

cranks over just fine, headlights seem just fine. The only goofy thing about charging problems is a few times my radio would factory reset.. its a 302

 

Sounds like you are losing all power to the cab.
The radio memory should be wired directly to an always hot wire before the ignition switch.
Have you checked the condition of the fusible links at the battery+ side of the starter solenoid?

Do your other gauges (temp, oil pressure, fuel) function normally?
That would eliminate a bad cluster ground.

 

ok, ill look into that. Yeah all other gauges work as they should. Im i just looking for blown fuses or bad wires?

 

The fusible links are colored wires with a little rubber 'flag' at the eyelet end connected to the battery + stud of the solenoid.
The insulation should not appear charred or boiled/blistered.

You say the charging light flickers and the gauge doesn't move.
The truck must be charging if the headlights are bright, the horn, blower etc... work.

After the truck died, were you able to hear the fuel pumps kick in briefly when you turned the key to run?

 

Alright ill take a peek.

Correct. that is where i am kinda confused. all electronics worked.

It never actually died i just put it in gear and it just bogged down real low and sputtered. but the volts stayed very very low. its the first time it has done that.

 

So the voltmeter -usually- works?

Maybe your truck just needs a new belt and tensioner???

 

yeah it has in the past this is the second time this past week it has acted up. and now it just seems to get worse.

back home this past weekend that is something my dad brought up as well, do they stretch that much. would i just be looking to make sure there is no slop or just the condition of the belt itself.

 

Both.
The belt can stretch or get glazed.
Always check the tensioner, not just the pulley.

 

Took the alternator in the other day. Turns out it was toast. I bought a new one and as of now everything seems to be in regular working order. Thank you for your help.