Alternator problem

Voltage spikes.

These cause all kinds of problems, including blown alternators.

--
I'm never going to grow up.

I know many engineers here work on cars, so ...

I am debugging my wife's Lexus ES300. The problem is that the OEM alternators (original and replacements) are not charging at idle. At idle speed, the alternator put out 8V to 10V, which is insufficient to charge the battery. At high speed, it does put out 14V. People suggested speeding it up by changing the front pulley (65mm) to a smaller one. I found a 45mm pulley that might work. But would that cause problem at high speed, including burning out the alternator, or worst?

I have the same problem with my car. It?s a 1999 Mercury Cougar. It idles at about 800 RPMs and that speed doesn't charge the battery unit the RPMs go to 1800 and above, while driving; the RPMs are often below this level too. I've measure battery voltage at different RPMs and confirmed this, also you can see the dashboard light up brighter once you step on the gas and get the RPMs up to 1800. My solution to this problem is; in winter (it's friggin cold here in central Canada) I put a battery charger on my car battery 2 or

3 times per winter. As soon as I notice that the electric windows are going up slower that they usually do, that evening I put on the charger. I've talk to ford about it and they deny the problem. I've gone through three alternators, until learning this the hard way and each time it was $500 to $700 to replace the alternator. Also if you battery is 5 year old or more, don't get it tested, just replace it with a factory replacement. If your battery starts to fail it will damage your alternator, then your have two things to replace.

Shaun

I know many engineers here work on cars, so ...

I am debugging my wife's Lexus ES300. The problem is that the OEM alternators (original and replacements) are not charging at idle. At idle speed, the alternator put out 8V to 10V, which is insufficient to charge the battery. At high speed, it does put out 14V. People suggested speeding it up by changing the front pulley (65mm) to a smaller one. I found a 45mm pulley that might work. But would that cause problem at high speed, including burning out the alternator, or worst?

I have the same problem with my car. It?s a 1999 Mercury Cougar. It idles at about 800 RPMs and that speed doesn't charge the battery unit the RPMs go to 1800 and above, while driving; the RPMs are often below this level too. I've measure battery voltage at different RPMs and confirmed this, also you can see the dashboard light up brighter once you step on the gas and get the RPMs up to 1800. My solution to this problem is; in winter (it's friggin cold here in central Canada) I put a battery charger on my car battery 2 or

3 times per winter. As soon as I notice that the electric windows are going up slower that they usually do, that evening I put on the charger. I've talk to ford about it and they deny the problem. I've gone through three alternators, until learning this the hard way and each time it was $500 to $700 to replace the alternator. Also if you battery is 5 year old or more, don't get it tested, just replace it with a factory replacement. If your battery starts to fail it will damage your alternator, then your have two things to replace.

Shaun

I few other things I remembered to keep your battery charged. When I warm up the car in winter, I step on the accelerator to get the RPMs above 1800 so that I'm charging the battery. You can also drive in a lower gear whether you drive standard or automatic while city driving, this will raise the RPMs. Another trick is to disable the automatic headlights and just turn them on manually when it gets dark out. In my car I pull one the relays out of the fuse box, the headlights are a constant drain on the battery, something like 20 amps.

I hope this all helps,

Shaun

[advise NEVER disconnecting the battery while running ]

The alternator output is not the constant '10V' that your meter reads, but has peaks and valleys. It's possible that the regulator would stabilize at almost ANY average voltage output to keep (1) peak voltages under the battery safe limit or (2) alternator field windings within safe duty cycle limits.

No-battery operation is not NORMAL operation, is not specified. So, a test with the battery missing doesn't give any useful information. And, if the peaks aren't detected/limited by the regulator, they could fry other electrical parts.

And I'm sure that they have some "special magnets" you can put on the fuel line to line the gasoline atoms up for improved burn and double the gas mileage.

Jim

Oh, did you have to tell him that! I love damage control!

Jamie

PeterD wrote in news:itlpdu$qi0$ snipped-for-privacy@speranza.aioe.org:

the battery acts as a filter capacitor,smoothing out the DC *PULSES* that the alternator outputs. your meter(DMM or analog meter?) may be reading the AVERAGE of the DC pulses,and if one or more alternator diodes are out,or leaky,it could explain the charging problem.

the guy who posted the Autozone/Advance Auto Parts alternator tester suggestion has the right idea.

so,that means you got away with it before.....maybe not this time.

He could be damaging the engine electronics with the spikes,and/or other sensitive electronics. that could be costly;an ECU is expensive.

--
Jim Yanik
jyanik
at
localnet
dot com

The smaller pulley won't cause problems at high speed, and many police cars use them, but your car may not use a conventional pulley but a clutch pulley, and I suspect this could be the root of your problem. Web sites dedicated to Lexuses or Toyotas should have more about this.

Check the quality of your alternator ground by clamping a battery jumper cable between the case and directly to the battery negative terminal. I had a VW that would put out an extra 0.5V when that was done.

Don't run the alternator without the battery. Alternator diodes aren't rated 400V PIV for no reason.

I am think about changing the pulley on the alternator, which is a standard part for many toyotas. My corolla idle at 1000 RPM, but the lower RPM of the Lexus might not have enough power output. I am OK which burning out alternators or batteries, since we already had 2 alternators and 3 batteries for the past ten years anyway.

I just did that, but no difference. Voltage remain under 13V until

1000 RPM.

I only disconnect it briefly to verify that the alternator output is below the battery voltage.

Is it a pulley, rather than a clutch pulley? The clutch pulley is adjustable, and perhaps it's not being adjusted right.

I don't think it's adjustable. The pulley is directly attached to the alternator rotor.

is the idiot light working? Switched battery voltage goes through the ignition switch, through the alternator idiot lamp and into the regulator. If this circuit is open, you rely on residual magnetization in the alternator to bootstrap it to producing output. This generally happens at a higher RPM. Current provided through the idiot lamp provides field magnetizing current to allow regulation at idle speeds.

Back in the 60's when engine run-on was a problem, we realized that adding a simple diode in series with idiot lamp (cathode toward alternator) stopped the run-on.

Simple marine alternators referred to as 1-wire types had the regulator battery sense and output terminals connected. The connection to the idiot lamp was not used. Those would not produce output until about 2000 engine RPMs since they rely on residual magnetizing energy stored in rotor.

Oppie

And how many milliseconds does it take to toast an ECU with overvoltage spikes?

--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

I should have included this link

Rowland provides parts to rebuilders and is a good source of tech info

pikes?

Battery acts as a current sink, and so does the head lights. I am having problem with undervoltage, not overvoltage. There are probably

20A to 30A current sink even without the battery.

Battery acts as a current sink, and so does the head lights. I am having problem with undervoltage, not overvoltage. There are probably

20A to 30A current sink even without the battery.

You sound like you know a lot more about this problem with this car than any of us do. I recommend doing anything you like until you either fix it or screw it up to the point where it won't run anymore. You don't want our opinions or advice, you want to impress us with your knowledge of charging systems. Sorry, we're not impressed, your charging system still is not working.

any

g

I follow reasonable suggestions, like grounding the alternator with battery terminal, as the other poster said. I just don't buy the idea of hundreds of volt surging into 20A to 30A of load. When i disconnected the battery, the head light dimmed, not brightened. So, i am getting too little power, not too much. Engineering is about trials and errors, and eliminating the unknowns, within reasons. I don't claim to know everything about charging.

Have you read my post about the idiot lamp yet? I've done a lot of work with alternators...

a

Yes, i read your post, but I have to research more about this idiot lamp first. All dash board indicators are normal. The car is running normal, except for not charging at idle. Thanks anyway.