Just for kicks, dose any buddy know how hot there alternator gets after a short trip? I just took a two mile each way trip to the store and came back and the alternator was to hot to hold your hand on. I ask because the last several days it barely turns over in the morning but then starts and runs great the rest of the day. Next day the same thing. Yesterday I started it twice to move it then it wouldn't start till charged. Once started the gauge shows full voltage in about minute or so. I thought it was the battery's but now I'm not sure. They are interstate just short of 4 years. Last set lasted 6 years 6 months. I went to where I bought them, Firestone, never again, and they wanted within $10.oo of what I paid for them three years and 10 months ago. I said where's my 45%? They had a long line so we didn't do any testing. Thanks for your help,
Chet

 

I just changed my alternator, they get hot. Keep in mind the alternator doesn't start to charge until the GPR shuts off. Batteries in the 3-4 years range are pushing it IMO...they never die at the battery store.

 

I know about the glow plugs, but the oil was plenty hot and it was 90 F outside so the glow plugs should not of engaged. I was just pulling at straws here. I was going to change them yesterday but Firestone really pissed me off. I don't think Interstate raised there prices 75% since I bought these things last time. I just didn't get a chance to go to Costco to buy new yet. I hope it makes it one more day, going with the family peach picking tomorrow.

 

Are you saying that the alternator doesn't output current until the GPR shuts off? ...

... Or that the batteries don't see any replenishment of charge until the GPR shuts off?

Can you clarify that?

Pop

 

The Alternators regulator doesn't get signal to charge the batteries until the GPR shuts off. I have an LED in the cab hooked to the GPR as long as that light is on the voltage stays 12V or less. As soon as the light/GPR shuts off the voltage goes up to 14.2.
You can use this to diagnose the "health" of your alternator and batteries.

 

I just went outside and put my hand on the alternator, It's been over two hours, and it is still pretty hot. I can leave my hand on it but it is hot. Have to check it in the morning before I start it. Won't think if it's draining the battery it would make it hot? Morning should tell.

 

You may well have weak batteries. Below I will list some instructions on Testing the Circuit to help you determine, or at least limit the possible issues.

The Alternator produces Alternating Current (A/C) regardless of whether the Glow Plugs are active or not. (Which, BTW, regardless of ambient temperature, they do activate initially when the key is in the Run position).

The Regulator does not close until it is excited by the A/C field circuit, the reason it shows a nominal voltage (about 11.4 vdc) when the Glow Plugs are active is because the draw a staggering 80-100 amps. That amperage following the starter which draws up to 742 amps pretty much loads the entire system of batteries, their reserve, and alternator output until the GPR Opens relieving some of the stress on the system.

And, FWIW: I get six years easily out of Batteries as I use a Battery Conditioner mounted in the vehicle. I just plug it in. Often, I don't drive my 7.3 for a few weeks at a time and them perhaps a few hundred miles in a day.

To determine the General Health of the Alternator, there are a few basic steps that will help you determine it.

NO LOAD BATTERY TEST:

Dis connect the negative Battery Cable from either battery. Before starting the vehicle after it sets overnight, use a DVOM and check the surface charge:

NO-LOAD TEST:

VOLTAGE PERCENT CHARGE
12.60V - 12.72v 100%
12.45V - 12.71v 75%
12.30V - 12.44v 50%
12.15V - 12.29v 25%

12.6 vdc is about the cut off for a Battery's lifespan. Not to say you can't get more use. This will help identify a failing or failed battery.

RIPPLE VOLTAGE:

Ripple Voltage Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" (+) terminal on the back of the alternator, (not at the battery).

A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.

ALTERNATOR LEAKAGE TEST:

Alternator Leakage Current, to check alternator diode leakage, connect the Multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.

Lastly, simply measuring the Output of the Alternator at the B(+) Post while it is running should be in the range of 13.6 - 14.2 vdc. Then measure at the Battery. There should be no more than ,5 - 1.0 vdc difference.

If this all checks out, perform a draw test on the Starter. There may well be a corroded, loose, damaged connection between the Battery and the Starter Motor. It should pull not more than 742 amps when starting the vehicle. Otherwise, if none of the above can be identified, its the starter wearing.

Hope this helps you in your process of identification.

 

Is this a typo? If not could you explain further?

 

Yup. This is the correct reason. In the charging system in the trucks our forum covers, it has nothing to do with the regulator waiting to get a "signal" from the GPR's status to begin charging.

That said, there ARE charging systems that have a delayed turn-on, and may be the cause of confusion. Our trucks do not have a delayed turn-on.

Though what another forum participant is observing is correct, the reason for it is not.

Pop

 

Thank you for posting this. Today was the day I had to have it start, and it didn't. I charged it for 30 minutes and it started. Drove it 50 miles and it restarted. Stopped on the way home, it did restart. So tomorrow I'll do some real checking and then buy new ones. This was good though, my wife's car does the same thing after two or three days setting. Mine just over night. I put a new battery in the wife's three weeks ago, but it still does it. I can use that test on her car to. I'd do it now but it is so hot. I can't work in the heat anymore. I've been thur a lot. First light tomorrow.

 

This is accurate.

The Battery not under a load, following a charge, and sitting for at least 6 hours, should maintain a surface charge of 12.6 volts or better.

This is a reflection of the batteries ability to move (-) Electrons through the plates to the (+) plate. I know this seems backwards, but it accurate. batteries make their Voltage from (-) to (+), not what one would think. that's why in DC Current, a (-) Ground is necessary.

Amperage is whats produced, pushed if you will by voltage. Lower voltage ultimately reduces amperage availability, regardless of how much you have [amperage]. The "System" is 12 vdc. Everything uses Amperage to light, run, illuminate, etc.

Our batteries are say ... 800-1000 amp capable. They are in Parallel, The starter (new, good condition) should "pull" approximately 742 amps or less

So, if you have an 800 amp Battery, at 12.4 (75%) you have only 600 amps being pushed out. This is where "strain" comes from AND the motor and load [starter in this case] gets way hot because of it - resistance = heat. And, a loose or corroded connection can reduce the flow rate up to 99%!

So, at 12.6 vdc, you have a 100% Battery. Below 12.6 the battery is not only loosing its charge ability, it also looses its reserve ability (what "saves" the battery every time we put it under a load, otherwise, they would be a single use item).

But, even more important is the amp hour of the battery. And, when it begins to fall of..... say 85% or so, they begin to strain, and ultimately fail in a short time frame.

A new Battery should, following a charge, be a minimum of 12.7 - 12.9 when performing this test as its result.

How to prevent the loss and get the most from your battery? It's basic chemistry. Keep it COOL. Everyone seems to be under the impression that COLD damages a battery. Presumably because they don't notice a failure until its cold. HEAT is the Batteries #1 enemy, hands down. That's one reason to ensure the blanket is on our batteries.

Check them quarterly, top off with only DISTILLED WATER, charge them to 100% individually, CLEAN the connections, weather they "look" like they need it or not, and, maintain a record of specific gravity. You will identify issues this way.

In response to Alternator not producing voltage at start up, remember in School when we used a magnet wrapped around a stator (Copper Core wrapped in Copper Wire)? it produces electricity whether is moved a little bit or wound as fast as one can go. The light was either dim or bright?

The distance and gauge of the wire determines the amount of output at various speeds. If you open an alternator, its the same. A stator surrounded by a rotor with magnets.

The Bridge rectifier and regulator only covert and control peak output. We just have HUGE light bulb at start up.

BTW: The main cause of Alternator failure.... The Bridge Rectifier. They generate an extreme amount of heat. Basically Diodes in series.

 

.
Heat hurts in two ways. Not only does it increase the rate at which the water component of the electrolyte evaporates, it also increases the "self-discharge" rate. This is the rate at which any battery will eventually lose all it's charge, even with absolutely no load imposed. All battery chemistries do this, and lead-acid is no exception.

Right behind heat as a killer of batteries, is sulfation.

Any time a battery is kept less than optimally charged, it is sulfating. The lower the state of charge, the greater the rate.

When my truck's at home, there's a 110-volt extension cord leading out to it. A "trickle charger" (maintainer) is kept under the hood on top of the fuse box, and the leads go to the driver's side battery. This helps to keep the batteries "top charged", and should help prolong their lives by keeping the "reserve capacity" optimal by minimizing sulfation.

It doesn't hurt to check the electrolyte level every six months or so, as dry plates kill batteries, too. When I service the electrolyte levels, I also perform an "equalization charge".

Google is your friend.

Pop

 

Good info, thanks for all of it. FTE law man says no reps for either of you though.

 

I repped both of them for you.

 

Thank you!