Electrical operation

More or less, yes this is correct. If the alternator fails, then the vehicle will run until the battery is too drained to run the car, and it will shut off.

Check this guide out: https://www.2carpros.com/articles/how-to-check-a-car-alternator

It explains the setup in a little more detail and some symptoms of a bad alternator vs. a bad battery.

Yes, but that is an over-simplified way of looking at it. A huge water pump fills your municipal water tower, and that pipe connects to your house. Which one supplies your house with water, the pump or the tower? If there was no tower, the pump would have to run twenty four hours per day. If the pump breaks down, you will have water until the level in the tower gets too low to develop pressure.

The alternator, which, by the way, Chrysler invented, and they copyrighted the term, is the electrical pump. The battery is the water tower, and the van's electrical system is the house. Until the engine starts, the battery supplies all the current for the radio, dash lights, computers, starter system, and all the rest of the electrical system. That will drain a good percentage of what is has stored. Once the engine is running, the alternator begins to pump current out to the electrical system, and it puts some back into the battery to get it recharged for the next time you start the engine. If it were not for the alternator, the battery would run drained in less than an hour of driving, and much less if the head lights or heater fan were on.

There are two times when current to run the van's electrical system comes from just the battery. One is when one of the six "diodes" fails. Diodes are one-way valves for electrical current, and all alternators use them. When one fails, the alternator will only be able to develop exactly one third of its rated current. Your van uses a 160-amp alternator which is huge. For many years, a common, large alternator was a 90-amp unit. With one failed diode, the most you could get would be 30 amps. That is not enough to run the entire electrical system under all conditions. The fuel pump and ignition system will draw around 15 amps. Two head lights and all the tail lights can draw another 15 to 20 amps. By this time, if you want to use the heater fan, radio, wipers, etc, the battery has to make up the difference while it slowly runs down over days or weeks. This is the equivalent of the water pump not being able to keep up with demand while the firemen are fighting the fire, so the tower has to make up the difference.

For the second time when the battery has to help, you must understand how all generators work. They use a coil of wire, a magnetic field, and most importantly, movement between the two. That is why we run them with the belt. Hey, this applies to my sad water story too. The pump is of no use unless a motor is running it. It does not pump any water anywhere if it is just sitting there. The faster it runs, the more water it can pump. The faster a generator spins, the more efficient it becomes. The opposite is also true. The slower it runs, the less current it can develop. An alternator's pulley is a lot smaller than the crankshaft pulley that drives it, so it spins a lot faster than engine speed, but in spite of that, at idle speed, it is possible for its efficiency to drop so low that it cannot develop enough current to meet demand. This is where the battery starts to supply the needed current. This is also where you might see the head lights dim, then they'll get brighter when you accelerate from the stop sign. This will be more noticeable when you're running a lot of accessories.

To add a couple more comments of value, an alternator is physically incapable of developing more current than it was designed to produce. If you need a replacement, and a smaller one will bolt to the engine, there is no problem doing that. A properly working electrical system will rarely draw 50 amps. Your 160-amp alternator has a lot of extra capacity built in that will never be needed or used.

The second exciting comment is the alternator will always only develop exactly the amount of current needed for the electrical system and to recharge the battery, and no more. That assumes the alternator, the voltage regulator that runs it, and the battery that stores it, are all working properly as a team. You could have a golly-zillion-amp alternator, but if the electrical system needs 57 amps, it is going to generate 57 amps. Sometimes someone wants to switch to an alternator with a larger capacity thinking that is going to solve some problem, but it is still going to develop only as much current as is needed, and no more. Very often there are two or three different current ratings that were offered for a certain model in a certain year, and when you need a replacement, only the larger one is available. Here again, as long as it will bolt to the engine and the pulley is the same, it can be used. It is not going to develop more current, higher voltage, or charge the battery any faster. You can carry a gallon of water in a gallon bucket or in a two-gallon bucket. You will not get the water there any faster and you will not get more water. What you have is the capacity to carry more water.

There is a potential problem to switching to a larger alternator. For many years, including on my 1980 Plymouth Volare that I used for teaching, there were three different size alternators that were used that year. The wire carrying the current to the battery and to the rest of the electrical system was large enough to handle the maximum current the largest alternator could produce, but, ... That wire had a fuse link wire spliced in it that was sized for the alternator that was installed at the factory. There is only one time in the life of an alternator that it will develop its full rated output current. That is during a load test performed by your mechanic. If you had installed a larger alternator but never replaced the fuse link wire with a larger one, it could be possible to burn that fuse open. Fortunately it takes some time for that to occur, and the full-load output current test only lasts a few seconds; just long enough to observe the reading, and that is usually not enough for the link to burn open. Newer cars, starting around the mid 1990's, use a regular fuse that is bolted into the under-hood fuse box. These do not have that delayed action characteristic, so a full-load test could blow that fuse. Again, this is only a possibility, and only when a larger alternator was installed. I do not see that ever happening to your van. Your alternator could power the space station with enough left over to give a boost to the space shuttle! I cannot imagine what the engineers were thinking when they stuffed that monster in there. I have four Grand Caravans and a Dynasty, and the largest alternator in any of them is a 90-amp, which is way more than I need.

I always love reading Caradiodoc's stories. I mean he brought up the long forgotten Volare, Now I am wondering if mom's old Volare is still parked in the woods at my childhood home, being reclaimed by nature.

The battery does not actually know to take over. It is connected to the alternator, and the alternator just stops charging it -or- continues charging, but not at a fast enough rate, so the battery drains. The same way that the water tower in his analogy does not "know" that the pump failed. It is just connected to the water system and the water comes from it, and the pump replaces the water as the tower drains. If the pump stops completely, or slows down, the tower is still going to feed into the system until it does not have enough water to do so.

Does that make sense to you?

Tee hee hee. Everyone needs to be famous for something, and my reason will never be for my "good looks"!

That Volare was the first car I bought new. Has the "Road Runner" package which was mainly stickers and a spoiler, but it included a larger alternator. Drove it the first two years through salt and slop back and forth to college, then it has been sitting ever since. Has 45,000 miles, and has never been kept in a garage. I am very sad to say it is badly rusted underneath, but in just the last two years it has bailed me out twice. I have to drive into town to use various wireless systems, and due to running the battery drained, flat tires, and once unknowingly dropping my key in the van, then locking myself out, I have had to walk home ten miles. Both times I just threw in a battery, dumped a little gas down the carburetor, pumped up one tire, then sped off into the sunrise. My friends yell at me later for not calling them. I "leap frog" both vehicles home by driving one for a mile, then trotting back to get the other one. I figure I get enough exercise that way to last me for a few months.

Checked it multiple times with a measured gallon of gas, and purposely running out, and found it consistently gets 28.3 mpg on the highway. That is with 4,400 pounds of steel, including chromed steel bumpers. Oil changes and other maintenance, and all repairs cost a total of $90.00 in the first 32,000 miles, then I stopped keeping track. The biggest problem is the tires dry-rotted, and one flew apart when coming down off the highway. It held air yet; just the tread peeled off, but thanks to my amazing ability to procrastinate, I had to thump my way into town with that tire the first time I got stranded. Finally replaced that tire, then the other front one started to do the same thing. That just means "drive slower"! I dream of having my friend restore it, but to make up for it, I bought the last of the 1993 Dynasty's when I was working for the dealer. That one will never see salt or snow. It will get its second oil change this summer, along with new coolant and brake fluid. One more trip to town and it will have 5,000 miles.

You ought to open up the museum of odd and somewhat forgotten Chrysler vehicles. Just saying ;). And we may be related somehow or another, because your ability to procrastinate tire changes is right up there with mine. I once drove four days (about three hundred miles worth) with broken belts in two dry rotted rear tires. I just took 15 psi of air out of them and went on a bumpy, but not unbearable, and slooooow ride. But I got my routes delivered on time.

Well it is more than needed, but there is no getting too much. The car is only going to pull the amount of CCAs needed to get it going (probably 600ish). 1200 is what you might need for a big diesel engine or something along those lines.

Remember too, the limiting factor is going to be the very small contact area between the teeth on the jumper pack's clamps and the battery posts. It is real hard to get 100 amps through those. The jumper packs work best when you connect them, then give them a minute to put some charge back in the battery.

I have always wanted to get one of those jumper packs, but I am concerned with how well its battery will hold up if it only gets used a few times per year. We had two at school, but those got used multiple times per day, and were always on their chargers.

Now that I have a like-new ten-year-old laptop with Windows XP to replace my unbelievably miserable Windows 10 pile, I spend more time sitting in my van to answer questions, and the little inverter has been draining my van's battery. I carry a spare battery and just use jumper cables. Got me going yesterday again.

As for the fuel mileage on my old Volare, only little light-weight plastic cars get that now, but they are horrendously cleaner out the tail pipe. I ran a service call to fix a tv in 1979, and that guy had a 1979 four door Volare. Said he was getting twenty nine miles per gallon, and I did not believe him until I bought mine a year later.

Yeah those jump packs are nice, but too expensive for how much I would use one. I just keep a pair of cables in the trunk and find someone with a big enough alternator on their car to give me a jump. Believe it or not, jumping a 2002 Blazer takes a good amount of juice. Always a struggle getting it to fire up when it goes out. And then the idle relearn takes a while so you have to keep feathering the gas or it will shut off again. I guess that is a pitfall of a cast iron engine.

Personally, I am a little suspicious of the cigarette lighter types. Just does not seem like you would be able to get that much juice through there. At least not enough for a quick jump start. I suppose you could push enough charge through there to charge the battery up enough over a few hours.

Yes, that is exactly what they are supposed to do. Most power outlets are on a ten or 15-amp fuse, so you cannot pass more than that from the booster pack. If you blow that fuse, the jumper pack will not work that way. The other potential problem is a lot of power outlets and cigarette lighter outlets only are powered up when the ignition switch is on. If you have to turn that switch on to make the jumper pack work, it is also going to be trying to run the instrument cluster, and all the other computers on the car. That can be enough to blow the fuse for the power outlet.

Mr. Heyman, this is the first I have heard about a GM product having to learn idle speed after the battery was disconnected or run drained. This is real common on Chrysler products, with a simple cure, but what do you have to do on yours to initiate that relearn?

Well at least I am guessing it is a relearn issue. It happens when the battery is disconnected for a while (like when I am working on something). I just have to get it started and then keep feathering the pedal for five or ten minutes so it idles. Once it will hold idle, I put it in gear and it probably stalls. Fire it up again and it is good to go. Weird I know. I had not heard of it in GM's before either. If I had to guess I would say that it feels like the IAC valve is almost completely shut and that is how long it takes to get adjusted. But that is not really an area that my know-how extends to. Plus it is not a big enough issue for me to find the time to dig in to it.

As for the sealed transmissions, yes they can leak. But it is not real often because they are usually very well sealed up. At least that has been my experience. If it is leaking, you will find pretty clear evidence of a leak by getting under the van and feeling all around the transmission pan. There should be some fluid around there somewhere.