Hey Guys easy one for you.
What should the volts be at idle coming out of the alternator?
Mine are like 11.4 volts.
Do you think alternator is weak or that something else is causing it.
ie: air pump removel kit ect..

Thanks,

 

The digital gauge in my '89 shows about 14.3v~14.7v when the car is cold. It drops to about 13.7~13.9 when the car reaches full operating temps, which is normal.

Is the voltage 11.4v only at idle? If you rev the engine, do the volts go up above 12v? I know some high-amp alternators produce less than 12v at idle, but produce a LOT of juice once the revs increase above idle.

 

Yes it's only at idle, when the engine revs it's normal. It is the original alternator from 88 when I bought the car. Has 57,000 miles on it.

Thanks,

 

Have the battery checked to be sure but it sounds like your alternator is dying. Check all connections including grounds to eliminate external factors.

 

I'll check it out. Guess it's time for a new alternator after 22 years.

Thank you,

 

If it's the original alternator that came on the car and your gauge is indicating less than 12v, it's probably on it's way out. Luckily, it's not an expensive or overly difficult job to replace the alternator.

When I replaced the one on my '89, I went with an aftermarket high-amp unit. Once it was installed, all the interior and exterior lights became super-bright, and I haven't had any issues since.


P.S. When the alternator died on my car, I had to have the car towed back to my house, about 60 miles away. The tow cost me almost $200! I learned my lesson that day, and I joined CAA (the Canadian equivalent of AAA) the very next day.

 

Yea I will go with a high amp one too. Once the weather changes that when I will start all my winter projects. I just bought a Richmond 6 speed for it too. I had enough of the 4+3..

 

CAA/AAA is worth every penny. Read the small print to find out all the stuff that is covered. Don't leave home without it.

 

I went with a 160amp unit (the stock is 105amp) from Motor City Reman http://www.motorcityreman.com/ Good company to deal with, quick shipping and a fair price. They also sell a 200amp unit, but this over-kill unless you're planning to run a competition-grade sound system.

I should also mention, according to their website they recommend upgrading your positive battery cable with a 4 AWG cable because of the increase in amperage. I had upgraded mine for a while, but then reverted to the stock cable and haven't had any issues at all.

 

It is normal for the alternator to put out 14.2-14.7 cold. There is a temperature compensating circuit utilizing a thermister in the voltage regulator.
When hot, the alternator output drops because they don't want to charge a hot battery to max amps, it might boil over, or explode. That's why there is the temp compensating circuit.
When hot, it puts out about 12 volts, but your digital dash has a voltage drop of aprox. .5 volts. This makes it look like it's deficient.

when you get home, have your significant other start the car when hot, and you open the hood and put a voltmeter on the battery, check volts.
Then have them put it in drive.
If they put their foot on the brake, the stop lights, 4 in the third brake light, and the 4 on the back of the car, plus the air conditioning, the ignition system, dash, fuel pump, and any lights, such as turn signals, and interior lights, is going to pretty much reach the 60% of the 100 amps the alternator is rated at. You will see your 12 volts minimum, maybe less.
When the alternator reaches it's rated load carrying capability for that speed, the amps will then begin to come out of the battery, and the volts on the electrical buss will be battery volts.
When you rev the engine, and the volts increase, it's because the alternator is above it's minimum speed for producing volts and amps, and THEN it has to charge the battery as well.
GM put too small an alternator on a car that they expect to idle at 500 RPM, and produce 105 amps.
At idle, the alternator will put out only 60% of it's rated amps.
I used to keep 2 spare alternator for summer time because the heat would kill them. after one would die, I would get another one installed, and run it till it dies, repair it, then run that one till it died, in the mean time, I would have the other two rebuilt and ready to go.
I have both repaired alternators for sale. for $50 ea. plus shipping.
Anyway,
I finally installed an LT-1 alternator on my '86 with an '85 upper alt. bracket with spacers, and no more problems.
I also use the stock battery cable.
If you don't live in the desert, you shouldn't have any heat related problems like I did.

 

Not correct!!! Cold and normal idle rpm, C4 alternators should put out 14.7 volts across the battery terminals and the alternator voltage decreases with increasing temperature and it should put out 13.7 volts at its operating temperature. The digital dash does not have any voltage drop. There is a 0.3 volt drop across the ignition switch contacts which makes the dash voltmeter read 0.3 volts low.

 

If it has never worked check that someone before you has installed under drive pulleys. The previous owner of mine did and they are steel and lok stock.

 

Ok,
FOR YOU NIT PICKERS
1.the digital dash is't exactly where the voltage drop occurs, I was merely pointing out that it would read low.
2. The hotter the alternator gets, the lower the output volts.......it's a fact.
On a 115 degree day, my alternator used to read a volt and change lower than it does on a 70 degree day.
3 different alternators, 15 years worth of operating with the same car, same temperature ranges, same gauges, same operator, same speeds, same loads, same engine, same pulleys,110,000 miles since I 've had it.

oh yea,
different tires.
But now,
with an LT-1 alternator, it is better regulated, higher output, and less heat sensitive.

 

One thing you might consider is to have your OEM rebuilt. We have a really good shop in my town who charged $52.00 to rebuild my OEM unit. Since yours lasted 22 years you obviously don't stress it. That way you keep the car more original.