I've noticesd my charging dial is always in the negative and my baterries are running down. I felt my alternator and it's hot . What's going on here? Do I have a short inside; bad voltage regulator?, what?

THX,

Buck

 

If the alternator case feels warm after the engine has cooled it is a good bet there is a problem with the alternator stack and/or regulator.
This would be consistant with the battery running down or low at the next start, from the drain.
The warm alt. case is a clasic sign of that kind of problem.
This kind of problem often still allows the alternator to recharge the battery and run the truck but never shuts down when the ignition switch is off.

 

With the engine running, disconnect the negative terminal from the battery and using a test meter get the voltage between the loose negative terminal wire end and the positive terminal. The voltage should be between 13.8v and 14.8v. Higher or lower and the alternator (or internal regulator) is bad. If the engine dies when the battery terminal is disconnected the alternator is bad also.

This is simple if you don't want to drive to your local auto parts store. they will usually test the charging system for free.

With the battery terminal wire disconnected, check the voltage between the neg and pos terminals of the battery. If the voltage is less than 12v you have a bad cell and will need a new battery. If the voltage is above 12 you may have a weak battery from a bad alternator, but it should recover after installing the new alternator.

 

I dunno what we're working on here, but never, ever, ever do this in an EEC III or newer controlled vehicle. PCM damage may result. It might not, but why risk it? This worked back in the days of contact points and generators, but don't do this on modern computer controlled vehicles, just ain't a good idea.

For starters, check across the battery posts at idle...voltage should be somewhere between 13.5-14.2ish, give or take a few tenths. Check voltage at the B+ terminal on the alternator at idle to ground, it should be the same. Check resistance from the B+ terminal on the alternator to the positive battery post, it should be pretty close to 0 ohms. Depending on what we're working on here, there's a few different paths we can take.

 

I'm not certain, but i believe the first paragraph here is a common myth.

 

Perhaps...but why risk it when a volt meter will tell you everything you need to know about the charging system?

 

Please dont disconnect battery while running. Older cars, yeah, but our super computers.....Anyways, just connect voltmeter between pos and neg on battery without disconnecting anything(that'll only tell you volts though, Amperage plays a part too). I think you already know it isn't charging. Alternators usually don't fry on their own. Gotta have a sub par battery, connection, drain, or an unusual load on the system. Autozone will test your battery and alternator, so those are fairly easy to do. Drains are a little harder to find. If you're not a wrencher, may be best to check battery, alternator, and cables yourself, but look to taking it to the shop for peace of mind for anything else. Of course if you wanna tackle it yourself, I'm sure my self and others can walk you through it. Good luck!

 

Measuring voltage, the test meter is placed across the connections. If you wish to measure currant. the meter is placed in series with the circuit. You will fry the meter in a split second if its not made to take 40 amps plus! The voltage reading will tell you if you need to replace the alternater. As stated with the engine running battery voltage should read 13.5 to 14.5 volts. If your alternator is hot when the engine is cold then the regulator pack is shot. Just get a rebuilt in this case (with long warranty). recharge the battery and check the voltage after it sits for a while. should read over 12 volts, if less than 12 its also on its way out.