Alternator troubles

I think I might be having trouble with my alternator, but need help narrowing it down to make sure it isn't the battery or something else. Tonight I was driving home and it was around mid 30's and I noticed that my headlights seemed a little dim with the engine running. I noticed they got brighter when I gave it gas and dimmed when the rpm's dropped. I haven't had this problem before. I went and tested the voltage output from the alternator about an hour after I got home (the engine still felt warm) and it was producing over 15 volts (I think it was between 15.1 - 15.3V). I didn't leave it running long enough to see if the headlights would dim, but they looked about normal. I took the belt off and spun the alternator pulley and it was smooth, but made a faint high pitch squeal. It is similar to a noise I have been hearing lately when cruising at 40 mph. It is the stock alternator, so I plan on taking it to get tested this weekend, but if it isn't the problem then no point getting it tested.

First of all, puh-LEEZE don't say RPM'S... It's Revolutions per minute.

Having said that, when you checked your battery voltage, was it with the parking brake on and the
car in gear, with the headlights on again? If you were in Park, you would have had greater RPM and voltage...

Also, if you have a "check-able" battery, it wouldn't be a bad idea to check the water level.

I typed the last post to quick and didn't have a chance to proof read it. I tested the voltage with the car in park with the headlights on. I didn't feel safe using the parking brake and I didn't have someone available to help. But come to think of it, I probably should have tested it in drive because that is when I was having the problem. I also tested it with everything on (heated seats, rear defrost, radio, and heat on high) and the voltage didn't drop at all. I don't think I have a check-able battery. It is just the standard AC Delco battery that fits our cars.

98riv wrote:

I think I might be having trouble with my alternator, but need help narrowing it down to make sure it isn't the battery or something else. Tonight I was driving home and it was around mid 30's and I noticed that my headlights seemed a little dim with the engine running. I noticed they got brighter when I gave it gas and dimmed when the rpm's dropped. I haven't had this problem before. I went and tested the voltage output from the alternator about an hour after I got home (the engine still felt warm) and it was producing over 15 volts (I think it was between 15.1 - 15.3V). I didn't leave it running long enough to see if the headlights would dim, but they looked about normal. I took the belt off and spun the alternator pulley and it was smooth, but made a faint high pitch squeal. It is similar to a noise I have been hearing lately when cruising at 40 mph. It is the stock alternator, so I plan on taking it to get tested this weekend, but if it isn't the problem then no point getting it tested.

You mention that you have a voltage reading at your alternator of 15.1v to 15.3volts at idle.
Have you done any of the voltage mod's like putting in the resistor, etc.???
The reason I ask that question is that 15+ volts at idle is higher than normal.
The rest of us get 13 to 13.5 volts at idle if your lucky with a good alternator and good battery with accessories running.
With those numbers your getting, tells me that something isn't right. The internal voltage regulator can be failing and will swing from higher than normal to lower than normal volts when they are about to fail. Also, a battery that is in not to good of shape can demand more current from the alternator and produce those kind of readings. One other thing is the battery thermistor breaking down or possibly fried. It can be faking out the alternator, just as the mod does, to increase alternator voltage. A constant 15+ volts to the battery on a non-modified system is telling me something is wrong and a few things need to be checked out. Need to properly load test the Alternator, Load test the battery and determine if it is on it's last legs and demanding too much from the alternator and not able to provide the lighting system with a steady amount of current necessary to give you consistent lighting.
You have to remember that the battery is the storage device providing all the necessary current for all systems in the car. The Alternators job is to replenish the battery, not supply the needed current to operate all current drawing components. So headlights that dim or get brighter depending on RPM's is either the battery, Poor/Dirty connections at the battery or the Alternator and bad connections at the alternator and on our cars the remote connector under the hood could have bad, dirty or loose connections.

I would start by removing all the electrical connections, one at a time and inspect for corrosion (green) and wire brush them to ensure good connections first. I'm referring to all the large cables starting at the Alternator and remote connector under the hood and then go back to your battery. Be careful not to touch any of these power connections to ground while you remove the fasteners and clean with a tooth brush size wire brush. To be safe, you should start at the Battery and remove those connections first. Disconnect your negative cable then your positive cable. Leave them disconnected as you work your way to under the hood. Be prepared to lose your radio pre-sets unless you have one of the small do-dads that plugs into your lighter with a standard 9 volt battery to save all the settings, including your seat settings, etc. They are inexpensive and I use one just because I hate having to go back and re-program everything.

If you find any connection with a large ball of corrosion on it, you can make a mix of baking soda and water in a paper or plastic cup and pour some on the bad connection. It will neutralize the corrosion and then allow you to use the wire brush for final cleanup. Any cable with some excess length to it can be put right into the cup and you can watch the neutralizing of electrolyte acid taking place. Have done it on battery cable ends many times over the years. I always keep a container of baking soda in the garage for this purpose.

Good luck finding and repairing your problem.
Rick

p.s. To hell with the perfectionist's that don't like the use of the abbreviation RPM's.
Been used for decades and don't plan on changing now.

Thanks for the help Rick! I will follow your advice tomorrow. I didn't see any dirty connectors yesterday, but I will go over them more carefully tomorrow. I don't have any voltage mods, so something isn't right. The battery is probably about 6-7 years old, so it could also be the battery is ready to go. It doesn't have any trouble when I go to start though.

98riv wrote:

Thanks for the help Rick! I will follow your advice tomorrow. I didn't see any dirty connectors yesterday, but I will go over them more carefully tomorrow. I don't have any voltage mods, so something isn't right. The battery is probably about 6-7 years old, so it could also be the battery is ready to go. It doesn't have any trouble when I go to start though.

Because the Battery has such a high cranking rating and the starter doesn't take much amperage to start a good running engine, could still point to a failing battery.
As I mentioned, the Battery is the storage device and the Alternators job is to keep it full.
All of the above mentioned things need to be checked now before the real cold weather sets in and starts really testing the battery. It still could be any one or more than one of the mentioned things that are causing the problem.
Now is the time to find and repair it, before it fails completely on you on some -10* night in the middle of nowhere.

I looked over the grounds and other connections and they all looked ok. The engine ground looked like it had a little green on the wire. I tried to unbolt it and clean it better, but apparently after 12 years the bolt didn't want to come out and it broke. So be careful when you go to remove it because it can break pretty easy. I ended up drilling a small hole next to it and bolted it down with a smaller screw. I couldn't use the same size bolt as the end of the connector because there was not enough slack in the cable and I couldn't get to the other side of the bolt. It is secure and doesn't move. Is that a good enough fix or should I get another ground cable and bolt it somewhere else? I am worried about trying to remove the bolt from the engine and it breaking on me and then I will really be in trouble. If I do replace it, what guage wire should I use? 4 or 8?

Edit: I have done a little reading and I saw this thread http://www.the12volt.com/installbay/forum_posts.asp~TID~102333 about running a ground from the alternator bracket to the chassis. Would that be fine to do? I plan on leaving the stock ground and running either a 4 or 8 guage wire from the alternator bracket to a spot on the chassis. Would there be any ill effects?

98riv wrote:

I looked over the grounds and other connections and they all looked ok. The engine ground looked like it had a little green on the wire. I tried to unbolt it and clean it better, but apparently after 12 years the bolt didn't want to come out and it broke. So be careful when you go to remove it because it can break pretty easy. I ended up drilling a small hole next to it and bolted it down with a smaller screw. I couldn't use the same size bolt as the end of the connector because there was not enough slack in the cable and I couldn't get to the other side of the bolt. It is secure and doesn't move. Is that a good enough fix or should I get another ground cable and bolt it somewhere else? I am worried about trying to remove the bolt from the engine and it breaking on me and then I will really be in trouble. If I do replace it, what guage wire should I use? 4 or 8?

Edit: I have done a little reading and I saw this thread http://www.the12volt.com/installbay/forum_posts.asp~TID~102333 about running a ground from the alternator bracket to the chassis. Would that be fine to do? I plan on leaving the stock ground and running either a 4 or 8 guage wire from the alternator bracket to a spot on the chassis. Would there be any ill effects?

Next time you're going to take out an old bolt, spray some PB Blaster on it and let it sit for an hour. Or, I like to heat the bolt up a bit and then spray it. 10 minutes and you can usually get em out.

I really doubt that the little bit of green you found on that ground strap is a concern worth worrying about. Those engine grounds are solid as bricks. Each strand in those things is like a 20 gauge wire. They usually always have some green on them. Unless it's cut or looks frail, I wouldn't bother.

Abaddon wrote:

98riv wrote:

I looked over the grounds and other connections and they all looked ok. The engine ground looked like it had a little green on the wire. I tried to unbolt it and clean it better, but apparently after 12 years the bolt didn't want to come out and it broke. So be careful when you go to remove it because it can break pretty easy. I ended up drilling a small hole next to it and bolted it down with a smaller screw. I couldn't use the same size bolt as the end of the connector because there was not enough slack in the cable and I couldn't get to the other side of the bolt. It is secure and doesn't move. Is that a good enough fix or should I get another ground cable and bolt it somewhere else? I am worried about trying to remove the bolt from the engine and it breaking on me and then I will really be in trouble. If I do replace it, what guage wire should I use? 4 or 8?

Edit: I have done a little reading and I saw this thread http://www.the12volt.com/installbay/forum_posts.asp~TID~102333 about running a ground from the alternator bracket to the chassis. Would that be fine to do? I plan on leaving the stock ground and running either a 4 or 8 guage wire from the alternator bracket to a spot on the chassis. Would there be any ill effects?

Next time you're going to take out an old bolt, spray some PB Blaster on it and let it sit for an hour. Or, I like to heat the bolt up a bit and then spray it. 10 minutes and you can usually get em out.

I really doubt that the little bit of green you found on that ground strap is a concern worth worrying about. Those engine grounds are solid as bricks. Each strand in those things is like a 20 gauge wire. They usually always have some green on them. Unless it's cut or looks frail, I wouldn't bother.

I did use PB Blaster, but I didn't let it sit long enough. I have to remember that the car is getting older and I have to be a little more patient when it comes to working on it.

Rick,
I ran a 4 gauge battery cable from the alternator bracket to the chassis ground (right under the trans line fittings we were working in the other day). Easy and no problems, unless you manage to damage the chassis ground bolt too

Got the battery replaced, still have an issue with the lights dimming with the rear defrost on. More annoying than anything else.

98riv wrote:

Got the battery replaced, still have an issue with the lights dimming with the rear defrost on. More annoying than anything else.

rear defroster grid draws a lot of current.

you could pull the alt and take it to (just saying) an Autozone, PepBoys or CarQuest for testing?!? Or maybe ask for any list member having a good spare he/she wants to unload, to PM you.

Albertj