Toyota FJ Cruiser Forum banner

21 - 40 of 59 Posts

·
Registered
Joined
·
990 Posts
Another thing to consider or look at is the condition of the belt and tension on that belt. If is polished or loose when the alternator is kicked in the belt my be slipping.


Sent from my iPad using Tapatalk
 

·
Registered
Joined
·
85 Posts
Discussion Starter #22
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.
 

·
Registered
Joined
·
3,638 Posts
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.
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.

Length 2118mm for the earlier models, 2150mm later models.
 

·
Registered
Joined
·
3,638 Posts
F-YAY -

Itsnotme made a valid point - you never actually stated what the measured values were of your voltage fluctuations.

Let's go back to square one and make some basic measurements to verify the system voltages with engine running and not running.

First, do you have a good quality digital multimeter? Not a $6 swap-meet toy, but a good quality ($30+) meter that will accurately resolve millivolts. This is necessary make meaningful measurements.

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 0.6 to around 0.8V to these values.

Make these measurements and let us know what you find.
 

·
Registered
Joined
·
229 Posts
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.
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.
 

·
Registered
Joined
·
3,638 Posts
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.
Do you currently have the voltage-boost diode installed in the alternator's voltage sense line?
(Typically replacing the ALT fuse in the engine-bay fuse box)

Finally, which of the three versions of the HKB voltage booster are you using: the fused version, the PTC version, or the adjustable version?

If so, can you replace the voltage booster with the original ALT fuse, drive the vehicle for one day, and then repeat the above measurements?
 

·
Registered
Joined
·
3,638 Posts
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.

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.
 

·
Registered
Joined
·
229 Posts
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.
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".
Unlike the OP, I can't say I had noticed any dimming of headlights, just the voltage fluctuations on the dash gauge. I have cleaned the battery connections.

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.
There's about a 1/4" of belt deflection halfway between the alternator pulley and the AC compressor pulley.
 

·
Registered
Joined
·
1,476 Posts
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.

Just sayin....
 

·
Registered
Joined
·
3,638 Posts
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.

Just sayin....
I'm going to second FamilyJ's observation on battery connections.

Over my years of wrenching, high-resistance connections at the battery terminals and/or battery/engine ground connections have been, by far, the most common cause of starting and charging problems.

If any of the battery clamps are deformed or corroded, or for some reason won't clamp tightly onto the battery terminals, just replace them with the Toyota OEM parts.
 

·
Registered
Joined
·
229 Posts
I don't think I could tighten them any more than they already are.



So nobody suspects faulty voltage regulators in these "remanufactured" Densos?
 

·
Registered
Joined
·
3,638 Posts
I don't think I could tighten them any more than they already are.



So nobody suspects faulty voltage regulators in these "remanufactured" Densos?
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.

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.

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?

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.

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.
 

·
Registered
Joined
·
85 Posts
Discussion Starter #35
Thanks everyone for all the feedback! I am young and dumb, and new to the car game, but I am learning, so I really appreciate the feedback. I think I just got ahead of myself at first and didn’t think through the problem as logically as I could have, as @FJtest pointed out.

I thoroughly wire brushed the battery terminals and terminal clamps when I replaced the battery, and again when I replaced the alternator, so they are very clean and bright. I also brushed and cleaned the ground point on the fender as well. I double checked the belt size and part number and they are correct. I’m not sure about slack in the belt tensioner, it felt very tight, but I would have to check and confirm.

I took some measurements a while back with a multimeter and an OBDII reader, but never got around to posting them here.

Rest (overnight in the garage) - 12.8 V
After starting - 14.48 V
Idle (cold) - 14.4 V
Idle (warm) - 13-14 +- 0.2 V fluctuating
Driving (2000 rpm) - 14.2 to 14.5 V

These were taken a while back, so I will try to get some new readings now with a better multimeter and I will post back.

These measurements are with the HKB mk3 with PTC electronic fuse installed. It does not have dual polarity, so I verified it is installed in the correct direction. I also tested with the factory 7.5 Amp fuse and got the same fluctuations, just 0.8-1 V less without the voltage boost.

The loose/deformed terminal clamp idea is interesting. I will definitely look into it and report back.

Thanks again for all the input, it’s very helpful to a beginner!
 

·
Registered
Joined
·
229 Posts
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.
The battery clamps sit all the way down and look fine, no visible deformation.

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.
Voltage drop across the battery terminal and the clamp with blower and headlights on: 0.0mv (positive terminal) and 0.7mv (negative terminal).

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?
Mine came from Rockauto, but I don't quite remember what kind of box it was.
@F-YAY Did you get your remanufactured alternator from Rockauto?

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 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.
Now I'm trying to decide whether to go ahead and replace the battery anyway (easy, but expensive) or get another reman. alternator under warranty (cheap, but a lot more work).

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.
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.
 

·
Registered
Joined
·
3,638 Posts
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.

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?

0.7mv would be seven tenths of a millivolt, or .0007 volt. It would take a high quality multimeter to accurately resolve 0.7 millivolt. If the voltage drop is actually 0.7 VOLT, this would indicate excessive resistance between the clamp and the battery post.

Mine came from Rockauto, but I don't quite remember what kind of box it was.
@F-YAY Did you get your remanufactured alternator from Rockauto?

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.

Now I'm trying to decide whether to go ahead and replace the battery anyway (easy, but expensive) or get another reman. alternator under warranty (cheap, but a lot more work).

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.

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? I wouldn't be totally unexpected to find that it WAS defective, would it?

I understand your suspicion of an auto-parts store running the battery load test, but you can insist that you observe the test. Otherwise, you can find an auto-electrical specialist shop who can run the test, again while you are watching.
 

·
Registered
Joined
·
229 Posts
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.
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.

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?
Nope, it's an auto-ranging 4000-count meter.

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?
True.
 

·
Registered
Joined
·
3,638 Posts
Did the results of a load test on the old battery indicate that it was likely contributing to your voltage fluctuations and was due for replacement?
 
21 - 40 of 59 Posts
Top