Resetting the PMU

Two days ago, the electricity went out, and my Mac G4 desktop, OSX 10.4.11 was on Sleep and it too Shut down completely. Tried to start the computer, but nothing. Looked up problem in another computer and followed directions on what to do. I disconnected everything, pressed the PMU reset button, hooked up the keyboard & mouse and the computer started up, no problem. Today, the same thing happened, went through the same steps as above. (Here in south Florida we have frequent electricity outages). I thought the battery was the problem, but after starting up the computer, all my settings - date, time, etc., are OK. That indicates that the battery is OK, no? Any idea of why I have to reset the PMU restart button to turn my computer on again? Should I change the 3.6 volt battery? Thanks

If the battery is more than a couple of years old it may be ready for a change. Low batteries can cause strange startup problems in Macs that are not predictable, consistent, or logical in manifesting their woes.
If you have a digital multimeter you can check the condition of your present battery. It should read at least 3.2V if it is the 3.6V half-AA battery type. Ideally this should be measured while the battery is under load; added recommendation from Hans777:
I have recently found out that an exhausted battery will still indicate >3.6 V with a high internal resistance VM.
Checking incircuit: powercord disconnected press PMU reset button for >about 5 sec before measuring.
Checking outside: load the battery with a 1500 Ohm resistor when measuring.
For a general reference: [Texas Mac Man's PRAM, battery, PMU tutorial|http://www.geocities.com/texas_macman/pram.html]
Message was edited by: Limnos

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Reset the PMU/firewire keeps failing after a bit

Ok, originally I was having trouble with a bunch of different functions after I replaced the internal battery and finally came to the solution of resetting the PMU button. I was experiencing trouble with the firewire ports before i reset everything also. Now all I have trouble with is the firewire ports not recognizing my external hard drive after I shut it down plug in another firewire device or audio front port device. I'm not sure what else i should do to resolve the whole issue. Help!?

Resolved!!! I followed the advice of article HT1939 about "Resetting Cuda/PMU on Power Mac": Disconnect ALL cables from the computer, including peripherals and power. I have disconnected the power cord last night and this morning I have pressed the Cuda button ONCE as described: do not press the button more than once before starting the computer up again. But the PM did not startup. I have opened it again and I have pressed it again once. PM MDD started fine, both the external firewire HD are correctly mounted on the desktop, but no internet connection. I have restarted with OS 9, opened I.E. 5.1 (how flashback!), internet started to work again as yesterday but now with the firewire HD on the desktop (thank you OS9).
Rebooted Leopard, now it is everything fine (net connection, firewire)
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Resetting the PMU with a non-Apple keyboard

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Thanks.
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What you are trying to do is reset the PRAM. Resetting the PMU doesn't need the keyboard at all: SMU.

Resetting the PMU daily

Hi all,
Since three days ago, every day I need to reset the PMU because my iBook 800 wont boot up. After the reset, it works fine.
So, not sure what my question should be, is this like the beginning of something bad to happen or is normal, or what should I do?
I love this computer and I don't want to lose it.
Thanks
Luis

Hi Ronda, all,
I have to add something, I guess I did wrong my testing.
Test #1, Leave computer off all night with battery in. Turn on with no power adapter only battery = failed -Needed to remove battery and do a PMU reset.
Test #2, Leave computer off all night with battery in. Remove battery, connect power adapter = failed - Needed to remove power adapter and do a PMU reset.
Test #3, Leave computer off all night with NO battery in. Connect power adapter = GOOD, no need to reset the PMU.
So, do you think there might be a problem with just the battery? The only thing I noticed, the battery holds about 2 hr of charge when is fully charged but if you look at the time remaining when is full charged, reads 5 hrs.
Thanks for all your help so far.

Q failure to wake and resetting the PMU

Every once in a while (roughly once per week, on average) my MacBook will not wake from sleep, no matter what I try. The only recourse is to turn it off and back on again, which is a huge inconvenience.
This seems to be a very common problem, and I've found many posts on it online. A frequently offered piece of advice is to reset the PMU, as described here
http://docs.info.apple.com/article.html?artnum=303319
However, this article states that resetting the PMU should be done only as a last resort, after one has tried to do things such as pressing the power button for 10 seconds.
Since my machine does respond pressing the power button 10 seconds, the above suggests that I should NOT attempt to reset the PMU.
My questions are: why is resetting the PMU regarded as something to do as a last resort, and would it be of any help for me to try it (considering that my machine does respond to pressing the power button for 10 seconds)?
Thanks!
tlm1905

Resetting the PMU does not affect the hard drive. Here's how:
http://docs.info.apple.com/article.html?artnum=14449
RAM chip contents vary depending on what you have open on your computer, and resets itself everytime you reboot the computer. The hard drive has its own swap file for RAM as well which varies with what is open, but it does not affect the contents of your data or applications. There are two kinds of RAM which confuses many computer novices:
The hard drive itself which is a spinning platter inside a rectangular case that looks much like an old LP player.
The RAM chips which are on a computer circuit board.
Only the hard drive stores actual data that you use and applications.
The RAM chips act as a buffer for multitasking applications, and the swap file on the hard drive act as an additional buffer.

How do you reset the PMU on an ibook G3?

My man just got a refurbed ibook G3 and on the first night it went to sleep and it won't seem to charge and I've read that the PMU needs to be reset but I don't know how to do this. Can someone help?

See this article:
http://support.apple.com/kb/ht1431
Jan

Resetting the PMU. How with my kind of Powerbook?

Hello,
I have the problem, not to know, how resetting of the pmu is done with my Powerbook G4 1,25 Ghz bought in December 2003.
I already read the article that is posted at the Apple Support (http://docs.info.apple.com/article.html?artnum=14449
), you even mentioned. But I cannot follow the instructions, because I think, the right type of Powerbook is not listed.
So it would be nice, if you can help me with this problem.
Thank You.

Your PowerBook is listed as: PowerBook G4 (15-inch FW 800)
15" 1.25GHz/12" 1GHz PBs, 2xPPC Mac minis, 12" iBook G4, Mac OS X (10.4.6) Cube, 2xTAMs, iPods 2G/4G, iPs, AEBS, AX

Screen dark & running fan, but I already tried resetting the PMU

Okay, my screen won't turn on. When I hit the power button of my iBook, I can hear the computer spool up and the fan comes on at high power.
When I try to reset the computer's PMU, nothing happens.
Here's what I'm doing, and the result:
1) Starting with the computer off.
2) Pushing COMMAND + OPTION + POWER BUTTON all at the same time.
3) Nothing happens.
4) I wait 5 seconds.
5) I push just the POWER BUTTON.
6) The screen remains dark and the fan turns on at high power.
Am I doing something wrong? Is there something else I can try?

Hi,
Try this site. Your symptoms sound like what Corey's talking about:
http://www.coreyarnold.org/ibook/
Post back.
Richard

How do I reset the power management unit on a Mac Pro laptop?

Screen flashes as the system alternates between battery charging and charging complete.
How do I reset the PMU?

MacBook Pro
MacBook Pro Apple Support

Is resetting the PRAM what I need?

After a power failure, my Power Mac (G4 1.25 GHz Dual Processor) will not go to sleep on command even though the System Preferences are set correctly. Other symptoms of the problem include getting the spinning wheel when I try to modify the System Preferences and it won't recognize my digital camera at ll when I plug it into any USB.
Is resetting the PRAM what I need to do? Is the only way to do it by going into the actual computer and pressing the button?
Right now I am in the middle of summer classes for school. Am I risking ANYTHING at all by resetting the PRAM? I CANNOT be without this machine right now.
Help is much appreciated. Thanks!

You said correct the "beachball"? What did you mean by that?
Because you said
Other symptoms of the problem include getting the spinning wheel when I try to modify the System Preferences
So, spinning wheel = beachball. Because you had a power failure, there is possibly damage to the hard drive directory, thus the spinning wheels.
How do I start up from the OS install disk?
Insert the disc into the optical drive, restart the machine, and hold down the C key on the keyboard while starting. In the window after you select the language, in the Menu Bar/Utilities, open Disk Utility. In Disk Utility, select your start up drive, and then select "Repair Disk". When done, close Disk Utility, and click Restart from the Menu bar. The machine will return to normal boot.
Do I do that before or after resetting the PMU?
No particular order, but you could run the Disk Utility first.
If after running Disk Utility the sleep command still doesn't work, the reset the PMU.

I do not arrive has to reset the pram of my Emac

Restart holding down command-option-p-r does no go for me on my emac 700
The only way I found : remove the battery
Any idea ?
Thank

Go Here:
http://www.whoopis.com/computer_repair/#imac
On the left hand side of the page is an emac link or just scroll down to about three quarters down on the page and look for a link called "emac.pdf" NOT "eMacatigraphics.pdf". Download the PDF and search in the document for PMU or PRAM it has instructions for reseting the PMU (PRAM). Basically there is a little button next to the battery under the access door (where the RAM and stuff is) to reset everything. Just follow the directions precisely and you should be fine.
Hope that helps.
eMac 1Ghz Mac OS X (10.4.5)

How do you reset the firewire and USB? My ports are intermittent. I suppose

How do you reset the firewire and USB ports? My ports are intermittent. I suppose it could be a hardware isssue, but still wonder if I can reinstall/reset the software without reformatting my drive.

Hello! Resetting the ports is done by resetting the pmu. press the button once with all external cables unhooked. Below is a pict of an example of the pmu location. Also an intermittent problem is often a bad cable. Tom
[IMG]http://img470.imageshack.us/img470/1623/mddlogicbd4ga.jpg[/IMG]

Resetting the battery

I want to reset the PMU on my iBook (because I placed a new battery and no matter how long I leave it to charge, it is always orange) and I found this:
http://support.apple.com/kb/HT1431#faq5
My question is this. Isn't it dangerous to reconnect the AC power adapter and then put the battery back in the computer?

No. It's perfectly safe to do it that way.
As a matter of fact, you can use the iBook without the battery in place (although I don't recommend it).

Red light near the PMU button

Hi, my iMac it's a G4 with 1.25GHz and gfFX5200.
It makes began to give problems with Kernel Panic. I have replaced the HDD and reset the PMU but it has not worked. Informing to me better I discover that the problem was given from inner RAM and I replace it. I startup the mac, the screen with the apple still and I shutdown from the power button. From that moment when I startup I find black monitor and a red light beside PMU button. Opening I have removed the thermal paste of the metal body and fear has overheated something. I have tried to replace RAM and HDD whit original and controlled that all she was connected well.
What means the red light? There is some way to save it?
PS: excused for my bad English, are Italian.

Ksola99, welcome to the forum.
The beeping that you are hearing is known as BIOS beep codes. They are to alert you to problems. Here is a guide to help you troubleshoot the problem:
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&dlc=en&docname=bph07107
There are codes near the bottom of the page. You should count the beeps and compare them to the charts to determine the problem.
Please click "Accept as Solution" if your problem is solved.
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I have a Mac G4 double mirrored model and everytime I shut it off it will not go on when I hit the power off button. However, if I unplug and plug in the power cord it boots fine and everything is OK. The PMU and logic board have been reset. Any ideas?

I have a Power Mac G4 double mirrored model and everytime I shut it off it will not go on when I hit the power on/off button again. However, if I unplug and plug in the power cord it boots fine and everything is OK. The PMU and logic board have been reset. Sometimes my Mac goes on just by pressing the power on button but most times I have to pull the power cord and put it back in. Any ideas or help out there for this? Could it be a failing power supply? Apple Care says that this model is obsolete so there is no help from there. John
<E-mail Edited by Host>

Hi John,
That's often a sign of a bsad Capacitor in the Power Supply, but...
Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...
http://eshop.macsales.com/item/Newer%20Technology/BAA36VPRAM/

Resetting the PMU

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