Alternator help!

Hi folks. My 04 2.7 has a problem with the charging system that's got me stumped. About a month ago, my battery light started flickering off and on. I had a lot of work done on the engine recently and decided that it might be a loose ground or connection somewhere. I found the ground from the battery and alternator that screws into the block was loose and tightened it up. Problem fixed.

Well, about three days later, the battery light is flickering again. After two weeks of driving like this, the battery barely cranked my truck last night at work. Odd thing was, after it cranked, the headlights were barely visible and the wipers were very slow. Should have been ok if the truck was running and the alternator good, right? So I put my multimeter on the battery with the truck running and got 9.1 volts. Gotta be the alternator.

Today, I took the battery out and the alternator off and had both checked at Autozone. The alternator passed the test and the battery just needed charging (obviously). The alternator belt is only a couple of months old and seems to be the correct tension and on correctly. I've checked all grounds I could find and they're secure and in good condition. I've checked fuses, ohmed the wire between the alternator and battery, and everything else I can think of. If the battery's good, alternator's good, no blown fuses, why am I still not charging? Help!

 

My dad's Honda had three bad alternators test good on that stupid autozone machine. Which leads me to say don't buy the cheap remanufactured ones at autozone. Junk.

 

Maybe your stealership will do a test for you? I bet they have better equipment, much as it hurts to give them the benefit of the doubt. When you push on that belt, you shouldn't be able to move it much more than 1/4" in either direction. I think 1/4-1/2 is the spec, but on my 1997 they still squeal sometimes when cold if I let them stretch to 1/2".

 

Thanks for the responses. I'm debating taking it apart and checking everything myself. Following the FSM, it diagrams step by step how to disassemble the alternator and test each component. May try to take it to Toyota tomorrow though cause that's a good idea.

 

I took my alternator apart once to clean the brushes after I got mud in it. It was easy.

 

i recommend having the alternator rebuilt should only cost 100 or so. Thats what it is around here. It's better than buy a reman and better than a new OEM unit because it is cheaper and will out last both

 

Do any of you know if there's a surefire way of testing the alternator while I have it off the truck to see if it's the problem?

 

not off the truck. But the dealer can do a load test on you charging system and that will give you a better idea. Man just have it rebuilt it will be cheaper than anything else. Plus you can have it wound up more increasing the amps.

 

So, I took my alternator to a local rebuild shop and they went through it and said its working just fine. Could my battery be the weak link in my charging system? What ground wires should I check?

 

Electrical issues are so hard to pinpoint. From my knowledge of the battery light in these trucks, it comes on when the alternator isn't supplying the proper voltage to the system. You should be able to pull the positive cable off the battery and the truck will still run off the alternator. I would check the power wire between the alternator and battery also.

 

PLEASE DONT DO THIS!!! This will kill a diode in the alternator. Check the grounds and positive cables. Also check ground straps to the chassis.

KISS Keep It Simple Stupid

 

could not agree more with this. get a wire brush and a good light and check the grounds, you would be suprised at how much dirt grease and crud can build up.

the easy simple things should be the first things to look for, 90% of the time that will solve the problem.

 

X2!!

Not only can you cause problems with your alternator, but the built in regulator uses the battery voltage reading to stabilize itself. If you run the engine without a battery connected, you could easily get voltage spikes above 18V, which can damage the sensitive computers on a vehicle.

As for the OP's problem: Check both of the white wires going to your alternator. One is the "Alt-s" wire, and is the input to the voltage regulator. If the Alt-s fuse is blown, or there is no power at the alternator from this wire due to broken wire, etc. then the regulator will not energize the field properly, and a perfectly good alternator will not charge.

Also, check the red wire from the gauges fuse and make sure that there is 12v at that connector for the alternator.

 

It's very likely that your alternator is going, I had charging trouble a couple winters ago and voltage from the alternator checked out ok so I thought it was the battery. Shortly after the battery light started to flicker then my truck died, I replaced the alternator and put the old battery back in and everything is fine since.

 

Thanks guys. I just got my alternator back today and will put everything back together and test all that.

 

I put my alternator back on the truck tonight and crunk her up. Everything seemed fine and I had over 14 volts at the battery with the truck running and no battery light flashing. Took it for a test drive and while waiting to turn at a traffic light sitting at idle the battery lamp is flickering again. I take off and as long as I'm above 1500 rpm the light goes out. I pull over and put my meter back on the battery and I'm barely getting 12 volts with it running. I switch everything on; ac, radio, turn signals, headlights, etc. and the reading goes up and down. So, at idle the output fluctuates and while under power it seems to work properly. What gives?

 

What have you installed?.. Sounds like high resistance in your circuit some where... or you have in decrease in Amps from the alternator.. I would test it at another location...

I had "good" results from Autozone when my battery was bad.

 

Replace the alternator.

 

While it may still be a control issue, sounds more like heat is taking it's toll on your alternator. By the time you take it off, and bring it to get it tested, it has cooled down. I have more of a feeling at this point from your recent post that your alternator is failing when hot due to a diode that is failing. At this point I would suggest replacing the alternator.

 

I think I FINALLY found my problem. Cleaned some connections this morning and switched it on to check voltage. Had a hard time getting voltage on the pigtail that plugs into the alternator. Checked the battery light and it wasn't on. So I had my son sit in the drivers seat and switch the ignition on. With the connector plugged into the alternator I had no battery light, but if I wiggled the wires in the connector, it would light up on the dash. Pinch the wires, lights up. Let go of the wires, goes out. Looks like a bad connection in the pigtail.

I'm going to buy a new pigtail and put it on this weekend. What's the best way to hook it up? Solder the wires together, wire nuts, or butt connectors?