Lately the voltage meter on my car has been swaying back and fourth a lot, and dropping below 12 volts. When I first start the car up it's fine and the volts read like 14 and the needle stays stationary, but after I've been driving the car for like 5 minuetes the volts start changing all the time. I have to keep the engine reved heavily just to keep it above 12 volts.

Only accesories going are the AC and radio.

So do I need a new alt, or is it something else?

 

Have you checked the belt tension?

I would measure the battery with a proper meter when your dash gauge is showing low voltage, and go by that.

It's possible that the regulator built in to the alternator is failing once it warms up.

Is the car starting without the aid of booster cables?

 

Fluctuating voltage readings are very common on our cars now that they are getting old. Many things can cause the dash Volts gauge to go wacko:
1. Loose or corroded ground connections.
2. Loose or corroded power connections.
3. Dirty contacts inside the ignition switch.
4. Funky fuses/fuse links.
The voltage at the battery is the most important thing to worry about. Below 12.5 volts will discharge the battery, needs to be at least 13.0 volts to charge it. Normal is 13.8 to 14.0 volts.
On my car, I have found that the cigarette lighter socket voltage is very close to the actual battery voltage (it does not go thru the ignition switch).
You need a volt meter(DVM) to properly check this.

 

By checking the belt tension, you mean checking to see if the tensioner is in the same spot right? Well I have checked that and the tensioner hasn't moved.

If the regulator in the alternator is failing than do I have to buy a whole new alternator?

The car is starting on it's own with no help. It starts up good and voltage will read about 14 for 5-10 minuets, then the voltage begins to fluctuate.

 

What is the best way to clean corroded stuff?

I checked all the fuses and they are fine, but not the fusible links. If a fuse isn't burned out could there still be something wrong with it?

How do I check the contacts at they ignition switch?

How much does a DVM cost?

 

I picked up a pretty decent DVM at Canadian Tire for $20, whatever your equivalent auto parts flogger is. Even a cheap one from the Wal Mart auto section is okay.

By belt tension I meant is the tensioner doing it's job - I wanted to confirm that the belt wasn't slipping.

Probably the best way to clean corrosion (if you find some) is with a soft wire brush, or stiff toothbrush. Take connections apart and clean them with one of those welding brushes with the brass bristles if you can find one reasonably priced.

 

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Thanks, for the info dawg.

BTW, I see your Oilers are making a late season playoff run. I hope they get in, but not at they expense of my kings.

 

OK, You ask some good questions. I'll try and answer:
Alternators ARE repairable, I've replaced:
a. The voltage regulator
b. The brushes.
c. The large diode bridge.
d. The small diode bridge that feeds the voltage regulator.
If you know EXACTLY what is wrong with an Alt, it can be repaired, but replacement parts cost almost as much as a rebuilt Alt.

I do NOT think you have a bad Alt.

The best way to clean electrical contacts is:
a. Spray the connection with “WD-40”, this stuff dissolves most types of corrosion and helps prevent from happening.
b. For pin type connections, unplug the connector and plug it back “in” (together), repeat at least 3 times ( most connector are “self cleaning”, the act pushing the pins together scraps away any “dirt”)
c. Scrub the metal with “Scotch-Brite”, this is less aggressive the “sand paper” and does a better job.
I cleaned the ground connections at the back of the passenger side Head and under the Alt bracket on my ‘83, which fixed my Volts gauge problem.

It is very rare for a fuse to go bad without burning up, but it can happen. That’s way most “experts” check fuses with a DVM.

The “best” way test the Ignition Switch is to measure the voltage coming out of the switch at the fuse block. The Ign Switch has 4 or 5 different sets of contacts for all the different circuits. This is much easier then trying to get at the switch itself.

A $20.00 DVM from Radio Shack should be good enough for you. More expensive meters have faster “response time” and come with better leads.

 

Thanks 83_1/2 L69, I appreciate the knowledge.

BTW, I know this is off the subject but I was thinking about getting one of those high amp alternators. What do you think about those? What are they advantages of having one? Do they simply just put out more power?

The reason I ask is because I'm getting some underdrive pulleys, and I'm probably going to get a sound system installed in the future. I want to make sure that my system stays charged, so is a high amp alt what I need?

 

I don't know anything about them, but my spidey sense says "big profit margin".

 

140 amp Alt is nice if you set at idle for a long time with the A/C on. Electric fans suck up a lot of amps.
I do not like Edelcrock water pumps on street cars, at idle, mine never flowed any water! (it worked great at higher RPMs)
A good UD pulley set only UD's the water/PS pumps and AC. The Alt should spin at "stock" RPMs.

If you do go for a bigger Alt, try finding a Cop Car alt for cheap.

 

Check out this site for Alt repair parts/Upgrades!

http://www.alternatorparts.com/gm_al...grade_kits.htm

Much cheaper the the local Auto Store.

Also look in Yellow Pages for a local automotive electrical repair shop. If you pull out your Alt and take it in to them, they can upgrade/repair your Alt for cheep.