While probably not contributing to your problem, be aware that the '07-'09 models used a belt with a slightly different overall belt length than the '10+ models. Installing the incorrect belt can cause low belt tension and belt slippage that's not visually obvious.Good point! On my second alternator change, I put a brand new belt on, just to make sure. I didn’t see any slipping of the belt on the alt. while running, so I think I can check that off the list in my case.
Here are my numbers:1. Measure battery voltage with the engine off and all other electrical loads turned off. If it has been 30 minutes or more since the engine was running, measure battery voltage at the battery terminal posts. It it has been less than 30 minutes since the engine was running, turn the headlights on for one minute, then turn them off and make your voltage measurements.
The battery voltage should be 12.6 to 12.9 volts at a battery temperature of around 70F for a conventional wet-cell battery, slightly higher for a properly charged AGM battery.
2. Measure battery voltage at the battery terminal posts with the engine running at a steady 2,000 RPM, and all electrical loads turned off.
The voltage should be 13.2 to 14.8 volts. If you have a voltage-boost diode in the alternator's voltage sense line, add .8 to 1V to these values.
Make these measurements and let us know what you find.
Do you currently have the voltage-boost diode installed in the alternator's voltage sense line?Here are my numbers:
1a. Battery voltage after the car had sat for 18 hours: 12.44v
1b. Battery voltage immediately after a 10 min drive: 12.77v
1c. Battery voltage after 1b and having had headlights on for 1 min: 12.34v
2. Battery voltage @ 2000 rpm: 13.80v
Battery is a 3-year-old wet-cell.
Like F-YAY, I installed a remanufactured Denso alternator (purchased from Rockauto) about 8 months/11k miles ago, except mine is 130A. Since it's a reman, it's impossible to say how many miles are on it and which parts of it had actually been "remanufactured".Itsnotme -
OK, I just realized that BOTH you and F-YAY are trying to perform the same failure analysis.
In your case, how many miles are on the alternator?
If around 100K miles, or less if the vehicle has regularly been driven in extremely dusty conditions, your alternator brushes may simply be worn out. They are easily replaced by removing a cover on the rear of the alternator, and the little brush module only costs about $15.
Your system voltages look pretty normal, but if you see variations in headlight brightness at idle, and you know all your battery connections are clean, I'd inspect the brushes if you are around 85-100K on the odo.
There's about a 1/4" of belt deflection halfway between the alternator pulley and the AC compressor pulley.Also, just to make sure its not a factor, verify that your serpentine belt tensioner is not at the end of its travel and allowing some slight slippage at idle.
I'm going to second FamilyJ's observation on battery connections.I went though all this 3 weeks ago, no need to go into the background because it's much the same, even had service techs check out the charging system and the AGM battery. Was about to buy a new battery, but went ahead and TIGHTENED THE BATTERY CABLES TO THE BATTERY even though they appeared to be plenty tight, and solved the problem.
Well, right there's a potential problem.I don't think I could tighten them any more than they already are.
So nobody suspects faulty voltage regulators in these "remanufactured" Densos?
The battery clamps sit all the way down and look fine, no visible deformation.Well, right there's a potential problem.
You have tightened your clamps so tightly (or have them positioned so high on the tapered battery posts) that they have "gone solid"; the clamps can't tighten any further because both legs of the clamps are touching each other. In this condition, you have no way to control how much circumferential "squeeze" the clamp is applying to the battery post.
Loosen the clamp bolts, spread the clamp legs, once again wire brush the inside surfaces of the clamps and the OD of the battery post, re-install them, push them down as far as possible on the battery post, and tighten the clamp screws with moderate torque.
After all this, there needs to be some gap left between the clamp legs.
If not, the clamps are probably deformed and need to be replaced, or the battery terminals are so distorted that you are going to have a hard time getting any terminal clamp to make good, reliable contact.
Voltage drop across the battery terminal and the clamp with blower and headlights on: 0.0mv (positive terminal) and 0.7mv (negative terminal).Another way to actually check the resistance across the clamps and the battery terminals is to do a "voltage drop" test. You will need a good quality digital multimeter that can resolve millivolts, and a helper.
Clean spots on the top of each battery terminal and on the clamp to bare, bright metal. Set your multimeter on the DC millivolt range (or lowest DC voltage range if it is an autoranging meter), and firmly press the + probe into the battery terminal, and the - probe onto the battery clamp.
Have the helper turn on the headlights, the HVAC blower to MAX, hit the brake pedal, etc. You should see a maximum voltage of only a few millivolts, reflecting the voltage drop caused by resistance between the clamp and the post.
Mine came from Rockauto, but I don't quite remember what kind of box it was.Denso alternators (and Denso electrical components in general) are among the most reliable in the world, that's why Toyota has chosen them as OEM fitment for decades. Same with the Denso alternators rebuilt by Denso.
Bear in mind that MANY different outfits "rebuild" Denso alternators and starters ... did your rebuild come from Denso in a new Denso box, or a generic "auto parts store" white box?
I would have already replaced the battery had it not been for the fact that F-YAY was having the same symptoms, but with a new battery and also with a remanufactured Denso alternator. Naturally, the alternator became the prime suspect.Looking at your voltage measurements, and assuming that they were made with a reasonably accurate multimeter, everything looks relatively normal except the voltage measured after turning the headlights on for a minute; it is slightly lower than desired.
I don't know if I trust auto parts store battery tests. Never had them test a battery and say it was good. They are in the business of selling batteries after all.Take your battery to some auto parts store where they can perform a high-current load-test. Even though only 3 years old, it could be showing the initial signs of early death.
Well, there was a small gap, but some people suggested I tighten it some more :lol:. I did make sure to stop as soon as the legs made contact, so shouldn't be deformed too much. I will redo it.The battery clamps sit all the way down and look fine, no visible deformation.
There should still be some small gap between the clamp legs when the clamping screw is properly tightened.
Nope, it's an auto-ranging 4000-count meter.Voltage drop across the battery terminal and the clamp with blower and headlights on: 0.0mv (positive terminal) and 0.7mv (negative terminal).
Your positive terminal voltage drop measurement looks fine.
However, is there any chance that you are misreading your multimeter, and the value you saw for the negative terminal is actually 0.7 volt instead of 0.7 millivolt?
True.Well, the only reason you would have taken a battery to the shop to be load tested was because it had already given some evidence of failing, correct? It wouldn't be totally unexpected to find that it WAS defective, would it?