Battery/Alternator output/death and possible water question.

Tim_Mobley · 06-29-2005, 06:32 PM

Hello again everyone. I had a really bad problem a few weeks ago with a misfire and nasty idle. Turns out I had a failed intake manifold gasket. So after a learning experience to be remembered, a friend and I got it swapped and working great. I have put approx 300 miles on the car with no problems. It is running great. However, on the way to work this morning, I noticed a slight lack in power in lower RPMs (at times making it hard to turn the steering wheel), accompanied by my dashboard battery light coming on for a moment. Once the battery light winked off, the car was back to normal. It was fine at higher driving speeds, no problems, no lights... So I figured it is probably my alternator or battery crapping out on me.

I have an electrical voltage tester I plan on using when I get home tonight to check it out. My question is how do I test the battery and alternator? Do I need to be at a certain RPM to test the alternator? Or does the car just have to be under load? What is the voltage supposed to be at idle on a healthy system? How about under load?

On a side note, on the way to work this morning, it was raining a LOT, and HARD. This was the first time it has rained since I did the work on the manifold, and unfortunately I was too lazy to put the passenger side splash guard back on the car after the manifold gasket swap. So since the alternator is right there, and I was going through puddles and lots of good rain, is it possible some water splashed up onto the alternator and the wetness was causing a bad connection for the power system under there at low RPMs?

BTW:

2000 Saturn SL1
Automatic
104,000 Miles
New ignition system (plugs, wires, coils)

I appreciate any help provided.

Thanks,

Tim Mobley

Robert-sl2 · 06-29-2005, 09:56 PM

water on an alternator will definately impair things. think of it this way, its job is to make electricity, electricity+water=bad news.

Anyways, put a multimeter across the battery teminals. under load and at idle it should read 13.8-14.8 volts. If this is not the case have the battery tested to see if it is the problem.

below is from http://www.uuhome.de/william.darden/carfaq5.htm

When the charging system fails, usually a "battery" or "alternator" warning indicator or light will come on or the voltage (or amp) gauge will not register "good". If you increase the engine speed and the alternator light becomes brighter, then the battery needs to be fully recharged and tested. If the light becomes dimmer then the problem is most likely in the charging system. The indicator (also known as an "idiot") light is a direct comparison between the voltage output of charging system and the voltage output of the battery. The next test requires use of a known-to-be-good, fully charged battery. Temporarily replace the old battery with this battery and run the engine at 2500 RPM or more for two minutes. Depending on the load and ambient temperature, the voltage should increase to between 13.0 and 15.1 volts during this period. Most vehicles with good charging systems will measure between 13.8 and 14.8 volts on a warm day, depending on the battery type that the charging system was designed for.

If a battery terminal's voltage is below 13.0 volts with the engine running and the battery tests good after being recharged or if you are still having problems keeping the car battery charged, then have the charging system's output voltage and load tested. Also, have the car's parasitic load, the electrical load with the ignition key turned off, tested. (Please see Section 10.) A slipping alternator belt or open diode will significantly reduce the alternator's output capacity. If the output voltage is above 15.1 volts with the ambient temperature above freezing, if the battery's electrolyte level is frequently low, "boiling", or if there is a "rotten egg" odor present around the battery, then the battery is being overcharged and the vehicle's charging system should be tested.

From Another Site

If you need to check the alternator, all you need is a voltmeter. Make sure you have a good battery. Start the engine and engage the clutch handle. Set the voltmeter on DC voltage. Take the red lead of the voltmeter and put it on the large red wire at the alternator. Put the black lead on the alternator housing. With the engine at high idle, you should have a reading of 14.2 - 14.6 volts. Take the voltmeter to the battery and place the red lead on positive and the black on negative. You should be reading 14.2 - 14.6 volts. If not, you have a wiring problem to the battery. If you do have 14.2 - 14.6 volts and you still have slow function problems, test the battery.

**Ssicarman** · 06-30-2005, 02:09 AM

Very good chance that you got water on the serpentine belt and it was slipping causing most your problems. Put the splash shield back on.

Tim_Mobley · 06-30-2005, 12:50 PM

Thanks for the information, guys.

The car had several hours to dry out as it sat at work yesterday, and I drove it home (15 minutes/15 miles) without any problems whatsoever.

I then got sidetracked with girlfriend junk, so I didn't get a chance to test the output, but will do that tonight.

The way in to work this morning was uneventful as well, so I am thinking it was just water getting up in there. I will replace the splash guard this weekend.

Thanks again for the help.

Tim