So I have a 83 f100 300 c6 auto
i have a head unit running 4 speakers I also have a 600 watt amp running two more speakers
I'm having power issues when my headlights are on I also get belt squeal when I'm having power issues and at first start ,
​​​the belt is brand new and if I run the heater as well the truck feels like it's definitely gone die
I can run the amp and radio as well as underglow and the truck is fine also long as the headlights and heater are off.
I've replaced the headlight switch, alt, battery checked all the grounds
I also replaced the rear harness to the tail lights cause of bad wiring
can any one point me in the right direction

 

Upgrade the alternator or lose all the add ons. Lots of threads on a 3g upgrade.

 

I've seen those threads but gosh what if it did the same stuff with none of that stuff hooked up to power?

 

Seems like you've got a combination of a very high electric load and not enough alternator output to compensate.

Have you taken a voltage reading at idle? That should give an idea of what is happening.

Also run a voltage drop test between the alternator and battery. Here's how:

1) Voltmeter (+) lead on alternator output wire. This is the heavy lead connected to the big insulated stud on the back of the alternator.

2) Voltmeter (-) lead on the battery (+) terminal. Not a typo, neg lead on pos terminal.

3) Run engine, turn on max electric load. Any reading more than 0.5 VDC indicates a problem with the alternator output cable. The closer to zero the better.

4) Repeat the test for the ground side of the circuit. Put the voltmeter (-) lead on the alternator case.

5) Put the voltmeter (+) lead on the battery (-) terminal. Once again, not a typo. Pos lead on neg terminal.

6) Run the engine and load up the electrical system. As before, any reading above 0.5 VDC indicates a ground problem.

For the squealing belt, try a few drops of belt dressing. You mentioned the belt was new but I've found them more prone to slippage than a used one. The slippage (squealing) is going to reduce the alternator output, so every little bit helps.

 

See now that's a real answer, it's not brand new and the squeal happens in the colder months at start up not in the spring fall or summer I'm wondering if the pulley on the front is wrong or needs to be shimmed?

 

I noticed you have some power woes...
Here's an easy way to fix them.
First, calculate your total load on the electrical system:
Lights, heater blower, accessories such as radio, amplifiers, heated seats ....yo get the idea.

So, how to?
Here are a few simple formulas to get the numbers you need.

P=I*E
Where P =Watts or Power
I = Amperage
E= Voltage
I=P/E
E=P/I

So in your case:
For the 600 watt Amplifier
600 Watts (P) divided by 12 volts (E)= a 50 Amp(I) load on the Alternator
Just for the Amplifier!
So, now determine the power requirements for every electrical item individually.
Convert all the requirements to Amperage (I) values using the appropriate
Formula above.
Add them all up.
If the total for all values adds up to more than the total output of your current Alternator then you have to make a choice,
Reduce the power requirements, or upgrade the alternator to higher rating for example from a 60 amp alternator to a 125 amp alternator.

Be mindful that as you produce more amperage you will need appropriate rated wires to handle the new loads.

 

I had a big post for this thread typed up last night and it appears to have disappeared. But the other guys have covered all but one point, and it was covered in a way - the alternator you have puts out essentially nothing at idle. In fact, you have to spin the engine to about 2000 RPM to get much output. In other words, you have more load than you have supply. So you have the choice to make that was already suggested - lose the load or replace the alternator with a 3G.

I said "3G" instead of "better". Some think the one-wire alternators, like the ones sold by Powermaster, are the way to go. I have one and it didn't put out much until you spun the engine rapidly. Turns out it is based on a very old GM design, and Ford's 3G alternator is a later and better design. Besides, the Powermasters have to be sent in for repairs, but you can easily buy parts for a 3G from the parts store or on-line.

 

The 130A 3G alternator is a common upgrade but note that the drive belt has limited traction.
A single V belt is only going to make about 100A before slipping (under any reasonable tension that doesn't kill the bearings in short order)
Glass beading the sheaves of *all* the pulleys will help.

This is why the 200A Mitsubishi ambulance alternators use a 10 groove poly-v belt.

If you have squeal on startup it is best to use a 3G with a 'Load Response Control' regulator.
This ramps up the load over a few seconds.
LRC regulators are available with 2-10 second ramps depending on their original application.

 

Amen! And going to dual V belts is a real pain. First, an alternator pulley with two sheaves of the same size is difficult, if not impossible, to find. Second, a crank pulley with three sheaves, two of which are the same size, is rare but available. DAMHIK.

 

The air pump belt is a skinny little thing.

 

This is the first thing I would look at, too, something seems wrong here.

 

Agreed, my general plan of attack was to verify exactly what it happening before going crazy with new parts, upgrades, etc.


Even though you have a "600 watt" amp, I don't think that's how much power the thing draws all the time. It's probably a misleading value for advertising purposes. Not quite a fib, but not exactly the whole truth. How big a fuse do you have feeding the amp? If the fuse doesn't blow, that should give a quick idea of the max amp draw.


Definitely check the battery voltage while at idle, and around 2000 RPM. Maybe even try it first with all the extra stuff turned off, to make sure the alternator is putting out normal power. You should generally see around 13.5 VDC at 2000 RPM to indicate the alternator is working. From there, increase the electric load and see if the alternator can keep up.


If the reading is low, try running a test jumper between the battery (-) post and the voltage regulator base. A marginal ground there can cause low alternator output.


I also suggested a voltage drop check between the alternator and battery to confirm there is no excessive loss of charging current. It's a very simple check, will only take a few minutes.


Back to the squealing belt, that indicates a possibility of one limiting factor. It takes X amount of torque to spin the alternator under maximum electric load. If the belt can't deliver that amount of torque, it will slip. Yours happening to be squealing, but sometimes a belt will slip quietly and your only indication is reduced alternator output. Make sure the belt tension is correct. Try the belt dressing and see if that helps increase the output. Don't just guess by listening. Take a before and after reading of voltage at the battery and see if there is any improvement.


You could easily have a combination of factors causing trouble. Low output with excess consumption is a bad combination, but rule out the easy stuff on the output side before digging too deep.

 

OK, maybe I'm being a little hard on the new guy, you are only 3 posts in at this point and I don't mean to scare you off. My apologies.

Now, what I told you is really not any different than those "real answers", which also happen to be very good answers. We need to know all the circumstances surrounding your problem and we really do not have any history. If the problem was present before you added the big amp, tell us that and while it is nice to know you have such equipment installed, if it is not operating at the time you experience the problem, well, it just is not relevant.

So, trying to be a little more helpful, let's tackle the belt squeal first. Is the belt in good condition and properly tensioned? You mention the problem got worse in cold weather. Belts will slip easier in the cold. Does adding load, (headlights on, stereo operating) change the symptom? Higher electrical loads transfer into higher rotational force required to turn the alternator. A weak or undersized battery will create more instantaneous load on the alternator. Adding electrical load will eventually cause the system to fail if the alternator cannot keep up with the demand to recharge the battery.

So, assuming a properly sized battery and a charging system of adequate capacity and in good repair, it is pretty easy to overwhelm the factory wiring of your truck. There is a primary power system starting with the fusible link at the solenoid and running through some barely adequately sized wiring and an ammeter circuit that can provide limits to the total electrical draw. Tapping in to say, your fuse block with high power loads can overwhelm the primary circuits causing the symptoms you describe. I believe you will find posts on using relays to provide a better power source for your headlights. Same can be said for the heater motor circuit. The stock wiring is adequate for these circuits while everything is in good order, but not much more. Check your ground cables including the battery cables and the bonds to the cab, rad cradle and firewall. Make sure your aftermarket equipment is properly installed and grounded. I hope you will find this general advice to be a little more helpful.

And yes, upgrade to the 3G alternator.

 

​​​​​​I'm not that new just a new account I've had the truck over 4 years, now to go 3g I'm struggling slightly to find the right diagram for my truck I've seen a ton of different diagrams if it helps it's a none ac truck with guage not light and it is a 4.9 also anyone have a idea on the correct belt size(s) for the v belt(s) I also have what looks to be a tribelt crank I've found a dual shelf pulley for the alt that has matching shelves any of the info requested above will greatly help me currently I'm waiting on the alt to arrive I have everything else besides the belts

 

Usually you swap your existing V-belt pulley over to the 3G so you use the same belt as well.
If your new dual sheave pulley is a different diameter than stock only you know what length belt *you* need.
The 4.9 takes the 8.25" mounting found in 3.8 V6 Taurus/Sable from the early '90's.

The light green/red wire coming from the cab connects to the light green/red wire of the new integral regulator plug.
The new fused output cable attaches to the fender mounted starter relay with the battery + cable.
Those are the only two alternator connections that are made to the truck.