1. Home
  2. Electronics Design
  3. Alternator problem

Alternator problem

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?

Reply to
linnix
Loading thread data ...

How are you measuring this voltage? Should be with battery and regulator attached.

Keep in mind that an alternator is basically a current-controlled current source.

Maybe you have a regulator or battery problem? Or an accessory sucking more current than it should? ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Should give out 14v all of the time. Can't understand that. Regulator maybe.

Reply to
HardySpicer

With the battery disconnected. The battery is 12.4V. Regulator is build-in the alternator. Just replaced the alternator (wasn't the problem).

People (web search) have reported same problem. It's a known design issue.

Reply to
linnix

Measure the current with the battery connected. Clamp-on thingie maybe, or just DVM the voltage drop in the wires.

John

Reply to
John Larkin

Battery should be around 13.2V with no load (6 x 2.2V)

My #2 daughter (the chemist) has a Lexus ES-something-or-other. They'll be here tomorrow for Father's Day. I'll ask if she's had any charging system issues. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Whoa! I just realized what you said... without battery. Where's it deriving field current ?:-)

Certainly it can't be a PM-type. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Sounds like a shit battery and possibly a body ground strap problem..

I don't know how you are measuring your voltage from the alternator but you should not be getting two different readings between the battery post and the back of the alternator output.

A good battery should hold the output of the alternator up...

Sounds to me that you are some how getting two different readings

Lets see.. Lets assume you are reading the alternator at some point where the battery isn't influences it. 8 Volts* 1.414 = > 12 volts.

And 10 Volt reading you have should be ~ 14.4 volts..

because the alternator generates AC into DIODES that give you peaks not seen otherwise with a DMM unless you have a battery at that point..

So, take the readings at the battery post instead of the alternator when it's running..

Jamie

Reply to
Jamie

I know this is a silly question but, "what does the dealer's repair shop say about it?"

I'd recommend NOT running the alternator disconnected from the battery. inductor, voltage spikes, electronic regulator... you get the point.

Changing the pulley sounds like a bad idea. It's already running pretty fast at cruising speed.

Another silly question. You're attacking a symptom. What's the PROBLEM you're trying to solve?

Reply to
mike

There's apparently an issue with the ES300 that involves internal separation of the harmonic balancer, causing slippage at low RPM (alternator torque increases at low RPM).

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

o

hat

I only disconnect the battery for the test.

Battery charged w my Corolla, which does not have this problem. My corolla is still running the battery swapped out of her Lexus.

Idle (700RPM): 12.4V w battery. 8V to 10V w/o. normal(2000RPM): 14V w battery.

y

Dead batteries. Engine stalling.

I think the problem is that the idle speed is very low (and quiet), and she does not want me to increase the idle speed (and noise).

Reply to
linnix

I only disconnect the battery for the test.

Battery charged w my Corolla, which does not have this problem. My corolla is still running the battery swapped out of her Lexus.

Idle (700RPM): 12.4V w battery. 8V to 10V w/o. normal(2000RPM): 14V w battery.

Dead batteries. Engine stalling.

I think the problem is that the idle speed is very low (and quiet), and she does not want me to increase the idle speed (and noise).

700 RPM idle speed is about right for the ES300. Are you having any problems with overheating at low speeds? A bad (slipping) crank pulley would also result in lowered water pump speed. Have the alternator bench checked and if ok then it must be low alternator speed at idle, or an accessory pulling too much current. A defective blower motor will pull a lot more current than normal. You tend to run the blower at higher speeds when using the A/C. Have someone check the crank pulley for separation, I think you'll find your problem there.
Reply to
hifi-tek

Not exactly sure how this is put together, but if you've got two chunks of metal slipping, it oughta be getting HOT and be easy to confirm.

Reply to
mike

Or put a grease pencil mark across the inside and outside sections and see if it stays lined up.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

M
t

to

le

that

or

is

n
p

tty

If that's the symptom, then you're not just lacking charge at idle, you're lacking adequate charge at driving speeds too. For half a century cars produced no charge at idle, battery capacity was more than enough to deal with that. Electrical load is greater today, but not so much so that a battery cant support the idle times.

I'd check you've got firm clean unoxidised connections, but presumably you've already done that. If not it might get you a trickle charge at idle, and charging at other speeds too. (Test with battery connected.) If not, best replace or repair the alternator.

A smaller pulley probably wouldnt do it, seeing as you've got insufficient charging over the whoel range of driving speeds. And at full engine revs, the alt would be liable to severe damage.

NT

Reply to
Tabby

Fix the problem with the alternator, don't patch or modify the system in an attempt to work around the problem.

It could be a defective alternator, (you say replacements, how many, and from what source?) or regulator, battery, or wiring. Also you cannot measure 8 to 10 volts on the alternator! The battery is 12 volts, so that is the minimum you'd measure. If you are seeing 8 to 10 volts with the system connected properly and engine idling, fix the problem.

--
I'm never going to grow up.
Reply to
PeterD

Never, ever disconnect the battery with the engine running.

Or the second alternator you got was also defective. That happens.

--
I'm never going to grow up.
Reply to
PeterD

Possibly he's blown the regulator (or something else) by disconnecting the battery while running anyway.

--
I'm never going to grow up.
Reply to
PeterD

You never disconnect the battery from a running alternator..!!

You'll get incorrect over all readings, on top of wild voltages appearing in your system..

Well, its your vehicle I guess, do what ever damage you like

Jamie

Reply to
Jamie

t

The alternator was never outputing more than 10V, so how can it blows the regulator? I have loose battery connections more than once, with car/alternator that are still running. Other loads on the system are enough to clamp down the output, to avoid serious damages. You guys never have loose battery connections?

According to this "Car Improvement" site, i just need "more power!!!". The 3000W machine can output 3 times more power than the OEM one. More than enough to power the electric seat warmers, and perhaps a fridge and microwave as well.

formatting link

Reply to
linnix

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.