Recently I have had the follwing symptoms with my 99 4Runner:

1. Running a little rough at idle when the heat/cool fan is on - turn it off and it smooths out.

2. I noticed that my headlights get brighter when I am parked and rev the engine a bit.

3. Windows seem to be rolling down slower than normal.

Does this sound like a bad alternator? I checked the battery voltage about a week ago and it checked out.

 

What is the voltage on the battery at 800rpm?

 

GENERALY:

A bad alternator will show a DROP in voltage when the engine is reved.

or, in my case, the alternator could go into full fielding, and put out full power. I had 17 volts at about 2000 RPM. Blew both headlights.

 

don't know if this helps, but always check for corroded or frayed wires. That's all i got. I don't own a four runner.

 

...and then at 1800 or so, plus one more measurement with the engine off.


(hey Gregg!)

It actually sounds like the alternator is fine, given that when you rev the engine you're getting a kick in voltage. That's somewhat normal - though it could be that the low-speed coils are toast. An alternator will have two sets of coils, one for the low RPM and one for the higher RPM. Hmm...

Let us know what the voltage numbers are and we can tell ya' more.

 

Take it to Autozone/Advance Auto Parts and they have a little machine they will wheel out to your car for free to test battery and alternator.

 

You can test it easy by starting truck, then disconnect the + battery lead from battery. If it keeps running, alternator is fine. If you turn on lights, etc. you might have to rev a lil.

 

#2 Happens to my 4Runner all the time. Sympotms started about 3 months ago. Headlights and heater blower power are insanely dim at idle, but since I live in the city where it's bright everywhere, I've mostly ignored it.

I had the oil changed at Mapplewood Toyota here in MN a while back, and they tested the battery and said it was putting out just over 12 volts, and that nothing was wrong with it.

Since that time, the truck has had trouble turning over at least half a dozen times. Mostly occuring after rapid starts and stops while doing errands around town.

My question is, if it's not the battery, and not the alternator (as the stealership told me), what could it be? This is not normal. My previous 2 wheel drive Toyota DL pickup never had electrical issues, and I put more than 200,000 miles on it with the original starter and alternator. By comparison, my 02 Sport only has 77,000 on the odo.

 

could be your starter if your having trouble getting the motor to fire

 

Thanks, Kyle. Hopefully that isn't the case. It's probably easier (and cheaper) to replace both the battery and alternator, than crawl underneath the rig and yank the starter. It should get me through the winter. Come spring when it's warm I'll investigate further.

 

Hey, I'm sure you've got this figured out already but for others who might stumble across the thread, I found this youtube video on bad alternator symptoms. Looks like it comes from this website here called talk to my mechanic where the help you figure out if you have a bad alternator. Whether or not it pertains to your specific issue with the 4runner, i'm not sure, but its at least a decent resource.

 

4 year old thread.. I hope he's got it figured out by now! LOL

5....

You knew what I meant!

 

5 years old. but yeah seriously.
Check dates people...

 

What if you hear a whistling type of sound? Has anyone had their alternator whistle before it going out on them? It's almost like a belt sound, but it can't be. I just had brand new Bandos installed 3 months ago.

 

You may have a loose belt

 

It could be a bad bearing.

 

more likely