'85 F250 351 w/upgraded 90 amp alt to operate snow plow. Current dilemma is that when I trigger the plow to move, the alternator belt screams as if it's loose and it is not. I thought the alt was seizing up, but when the original belt broke I could spin the pully freely with no grinding/bumping/anything. New belt caused problem to disappear for a day or two, now it's doing the same thing.

 

What kind of belt are you using, multi-grooved serpentine or v-belt?
If v-belt, how many v-belts on the alternator pulley?

 

Good question. My 84 has a two belt pulley, even on a wimpier alternator. Will make a difference!

 

Are you running one battery or 2? Because the battery is the shock absorber in a current load, and if you are running one battery, the plow is drawing too much from the alternator, and causing it to overwork. Second question... what cca (cold cranking amp) battery do you have? My suggestion is to add a second battery to help absorb the current overload.
Gary

 

A Battery is for starting the Engine only and not to run any equipment.

All Alternator Manufactures say their Alternator is for maintaining a battery and not to charge it. If you have a large capacity Battery and run it down you will burn out the alternator. For example all new police cars have hi-output Alternators and they have a sticker on them that says do not jump start, tow to a shop and use a batter charger. Newer Alternators have no current limiter and need a fuse link between the Load split and the battery to protect the alternator. Another example is a 1988 Ford has two 10GA wires from the Alternator to the Load Split and then one 10GA wire to the 14GA Fuse Link that hooks to the Starter Solenoid and on to the Battery for maintaining the charge.

If you have a larger loads then you need an Alternator to match the Loads and take your power off at the Load Split and not the Battery.

If you install a larger Alternator then you need to rewire the circuit from the Alternator to the Load Split, Fuse Link and to the battery.

A second Battery will just make things worse.

 

Appreciate the input.... a few answers... I have ONE battery and ONE v-belt on a single pulley, came with alt. I did think about getting a double pulley to run off of the extra crank pulley that used to run the air pump.
90 Stang, the "overworked" concept occurred to me too, that alt seems seriously hot when working... maybe the screeching is from too much heat? Not sure of the CCA.
SubFord, I'm a mechanic only when desperate, what is a "load split"?

 

Load Split is where the load of the truck can draw from both the Alternator and the Battery if necessary.

The Load Split in the Diagram below is where all 5 10GA wires come together just to the right of the word SHUNT. The diagram is for a stock 1988 Ford 150 series.

You also need a double pulley for your problem but if the Alternator is running hot you may need a bigger alternator also.

 

Well, Subford, then my teachers Macmillan and Costello were wrong.. they were techs in the field for 20 years, and both of them stated and so did the book, that the alternator puts out ac current and is changed to dc current via a diode trio, and the battery acts as a cushion for the surge in the power... like a shock absorber. Yes, a battery is used to start the vehicle, but on modern day cars, if you unhook the battery it will signal the alternator to put out more voltage, and could short out the computer because it works on a 5-6 volt feedback. If the voltage spiked to say 16, that would in turn be like 8 volts going to the computer. Thats why they say never unhook a battery from anything with a computer because it will fry it. I drive a tow truck with an electricpowered hydraulic boom, and if I only had one battery, that thing makes my alternator scream (believe me, I had 2 dead batteries in a 3 battery system) before. The truck also has a 120 amp alternator on it.... Sorry, but I understand where you are coming from I can see what you mean, but when an extra load is put on the alternator, it needs to cushion it. I am just stating what people in the field have said, and what I have seen. I am not trying to insult your confidence. Go to thelocal junkyard, pick up a battery for 20 buckswire it in.It won't hurt it. I do agree the double pulley will help. Gary

 

Quote:

Originally Posted by 90stanglx

Well, Subford, then my teachers Macmillan and Costello were wrong.. they were techs in the field for 20 years, and both of them stated and so did the book, that the alternator puts out ac current and is changed to dc current via a diode trio, and the battery acts as a cushion for the surge in the power... like a shock absorber.

This is true, it’s called a filter capacitor. I did not reference this, that I know of.

Quote:

Originally Posted by 90stanglx

Yes, a battery is used to start the vehicle, but on modern day cars, if you unhook the battery it will signal the alternator to put out more voltage, and could short out the computer because it works on a 5-6 volt feedback. If the voltage spiked to say 16, that would in turn be like 8 volts going to the computer. Thats why they say never unhooked a battery from anything with a computer because it will fry it.

Not exactly, there is a 5V-power supply inside the PCM that outputs 5-volts for making measurements and returns in a closed loop. If you unhook a battery while it is running it will go to well over 120 Volts and you are right that it can take everything and fry it. If it is unhooked it can not signal the alternator to do anything. The 5-6 volt feedback is from the stator to the regulator for self-excitement.

Quote:

Originally Posted by 90stanglx

I drive a tow truck with an electricpowered hydraulic boom, and if I only had one battery, that thing makes my alternator scream (believe me, I had 2 dead batteries in a 3 battery system) before. The truck also has a 120 amp alternator on it.... Sorry, but I understand where you are coming from I can see what you mean, but when an extra load is put on the alternator, it needs to cushion it.

I started working as a Mechanic in a garage in 1964 after taking an Auto Mechanics and Diesel Master Course and later an Electronic Course. I had further Training at the University of Oklahoma in Computers and worked as an Electric Technician until I became the Electronic Technician Supervisor. I have never heard of anybody saying anything about a cushion for an Alternator.

I try to learn something new every day and some of what I said I learned while visiting an Automotive Electric Rebuild Shop and then checking out what they told me with Alternator Manufacturers.

And yes what Mr. Macmillan and Mr. Costello said was right for the time when there were Regulators with current cutouts. Times have changed and in two years the Alternator will be built into the flywheel and it will also act like a starter and the system will be 36 volts.

Sounds like you need dual Alternators on that truck

 

Well, I know that I use my truck every day, and it works great when all the batteries are good. I have lifted a 16 ft van box truck with it, and it is a 73 chevy 3.4 ton turned into a tow truck. I took my class back in 2001 @ uti... and if the batteries are wired up parallel, it ups amperage. if in series, its up voltage. I understand that a capacitor stores current to supply when the need is low, with amplifiers, and sound systems. They just explained that the battery was a shock absorber. not a cushion. My fault. to help balance the charging system. If I am wrong correct me... I am half tempted to go retrieve my uti books from my garage that is 10 miles away... Just to reference it. Anyhow, well, we both came to the same conclusion. Gary

 

Simple concept...I use several Key machines in my Van, One Marine 1000 CCA Battery connected to an 1200 watt inverter (Changes to 120vac) Both batterys (The Starting Battery is an 885 CCA Battery, its purpose is to keep Both Batterys charged while the 130 AMP alt is charging. I have the normal sounds of No Battery belt slipping when all the current is supplying my needs to do my key cutting skills. My 86 Super Sport Van also runns lights on the inside and a laptop computer for other codes.
If your belt isnt a good belt, it will slip and cause you to loose power when you need it...a mis alighn belt would slipped or even a too tighten belt woulf cause it to drag...
I don't have any problems with my circuits.

 

I think that both of you are saying the same thing but in different ways. I have been a Master Electrician for over 30 years and have also done extensive martine and automotive wiring during that time. The thing to remember is that the electricial system is just that, a system comprising of many parts. It's basically the weak link in the chain situation because all components must do their individual job properly for the system to properly function. When any of the components fail, it puts undo pressure on the other components to take it's place causing problems. In the case of the newer vehicles (less that 15 years, those problems can have catastrophioc results.). I like the thought and anaolgy of tyhe battery acting as a shock abosorber in that it can absorb and balance out voltage spikes due to unbalanced current being emitted from a faulty alternator (even though I will admit that is not the battery's prime job). I also understand the point of a proper alternator. I think the point both of you folks missed is that how it works doesn't really matter in this case due the fact that it's NOT working properly.
My suggestions are as follows:
1. replace alternator belt with either a serp belt set-up or double belt providing alternator is sized properly for the application.
2. A back-up battery is always a great idea -providing certain considerations are addressed. I.e. same type battrery, proper load distribution, proper charging set-up (battery selector switch), and proper parrellel conductor lengths and sizes maintained.

The electrical theory discussion should remember that the purpose of problem solving is to solve the immediate problem in the most efficiant manner not necessarily who is right. A mind is like a parachute, it anly functions when it's open.