Alternator Help

[Bonnell]

Hi Everyone,

Last week I had a blowout and then found that my spare was flat. I had the car towed to the local Goodyear store and they put new tires on all four wheels.

I was leaving the dealership and I noticed that my voltage was less than 12v and that I could hear a whining sound from the engine compartment.

I took it back and they tested the alternator and found the same - that it was producing 11.7v. The serpentine belt was also cracking pretty badly.

SIDEBAR- I have seen a post indicating that the digital dash was pulsating and the person was told that the alternator was going out. I had noticed the same thing (very subtle but noticable).

They replaced the alternator and belt.

Here is the issue:

When I first start the car in the morning, the voltage is at 13.9 or 14 volts. After I am on the road for a few minutes, the voltage settles at about 13.6v.

If I come to a stop for any length of time, the voltage may drop to as low as 13v. As soon as I have 700-800rpm or better, the voltage goes back up ok.

Coming home from work, the same happens except that if I stop, the voltage may drop to as low as 11.9v.

This is with the running lights, radio, and AC on. The AC blower sometimes runs at high speed and it affects the voltage by .1-.2 volts if I am stationary.

The only difference between morning and evening is the temperature (~80 am & ~95 pm).

If I am parked (~600rpm) and all accessories are off, the brake lights seem to lower the voltage. If I park, place the emergency brake on, release the brakes (brake lights off), the voltage is ok. If I have the car in park with no brake lights, the voltage is ok.

I have no problem starting the car.

Goodyear says that the alternator has a limited lifetime warranty and will replace it if ther eis a problem. The alternator has Delco stamped into the case.

Again, when I first start the car in the morning, it holds 13.8-14.1 volts no matter what is turned on.

What do you think???

Thanks,

J

:confused

 

[vader86]

I think its fine, except for the 11.9v reading.
Although the GM voltmeter in the dash sucks, you can't trust it. Mine is off by almost .6v

You can take it off and go to Autozone and have it tested for correct amperage, but i think it'll pass.

The pulsation you had before was probably a combo of voltage regulator and bad amperage output.

Could also be time to change the battery.

 

[Bonnell]

Thanks for the response. I have wondered about the battery. I would have thought that I'd have a problem starting if it were not charging or holding a charge.

I worry about the voltage because a voltage regulator typically needs about one volt greater input than the expected output in order to supply the output desired. That is a general value but it would be sufficient for silicone or germanium unless there is another loss factor in the regulator.

What I don't know is how the fluctuation affects the overall system or the charge process (since I travel mainly on the interstate during the week, the voltage is almost always ok - higher rpms).

I'm glad that you don't seem alarmed.

 

[HTRK-1]

Your voltage should never drop to 11.9v when the car is running. It sounds to me like the internal regulator is breaking down under high heat conditions. I would replace the belt and alternator ASAP or it will let you sit. From what I've heard the alternators in the L98's are know for having this problem.

 

[oldace84]

Are you using undersized pulleys?????
thanks
tony

 

[Bonnell]

Thanks guys.

HTRK-1
I just had the alternator and serpintine belt replaced (one week old). The new alternator acted like this from the start. Is the regulator in the alternator?

Oldace84
I don't think that the pullys are undersized. I have not changed them and they are the same that worked for the original alternator.

Do you think that I just got a bad replacement?