Thinkpad T40 always thinks its on AC power. Any ideas?

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tselling · #1 Post by **tselling** » Sat Aug 12, 2006 2:54 pm

I recently picked up a cheap T40 as-is on Ebay to fix up to give my Grandfather (upgrading him from a T20). It always seems to think that it is on AC power. The battery LED is always on even when not plugged in. Battery Maximizer shows plugged in even when not and it always shows that it is charging even when not plugged in. Other than this the motherboard works fine. Battery charges up fine and works fine on battery and on AC. Just seems to think it is always plugged in. I ruled out the original non-oem battery by replacing with a new oem one.

Any thoughts how to cure this without replacing the motherboard?

smugiri · #2 Post by **smugiri** » Sat Aug 12, 2006 3:29 pm

My take is that the little spring contact inside the yellow power supply connector at the back is jammed in the on position.

Jiggle it a little with something or replace the connector, not expensive and does not require a new motherboard but the job requires some disassembly/re-assembly.

Alternatively, send it to me and I will send you a very nice "Thank you" note.

tselling · #3 Post by **tselling** » Sat Aug 12, 2006 4:32 pm

I have already replaced the yellow DC-in jack with a spare I had (the original one was kind of loose).

#4 Post by **bill bolton** » Sat Aug 12, 2006 8:38 pm

smugiri wrote:My take is that the little spring contact inside the yellow power supply connector at the back is jammed in the on position.

That has nothing at all to do with determining whether there is an external DC supply present or not.

A T4x ThinkPad will normally react in exactly the same way if you pull the AC power plug for your plug pack out of the wall socket or pull the DC connector out of the back of the ThinkPad.

Cheers,

Bill

smugiri · #5 Post by **smugiri** » Sat Aug 12, 2006 10:03 pm

bill bolton wrote:
smugiri wrote:My take is that the little spring contact inside the yellow power supply connector at the back is jammed in the on position.
That has nothing at all to do with determining whether there is an external DC supply present or not.

A T4x ThinkPad will normally react in exactly the same way if you pull the AC power plug for your plug pack out of the wall socket or pull the DC connector out of the back of the ThinkPad.

Cheers,

Bill

Being of scientific bent, I decided to do some tests to see how this works: I used my T40p.

1st test: plug power supply into Thinkpad but keep the AC side unplugged from the wall. Thinkpad knows that it is on battery power

2nd test: plug in power at the wall and at the Thinkpad's DC in port: get a beep and Thinkpad now knows that it is on AC power.

This seems to suggest that this is an electronic (or software?) problem and not a hardware one. One of the devices that I have installed in my hardware control panel is the Thinkpad power adapter, do you have this too?

tselling · #6 Post by **tselling** » Sun Aug 13, 2006 8:14 pm

It doesn't seem to be a software problem since even when the machine is completely off and not plugged in, the green battery led is lit.

I was thinking maybe it was the docking station connector... but blew it out pretty good in case there was something caught in there but no change.

#7 Post by **bill bolton** » Sun Aug 13, 2006 8:49 pm

If you remove the battery while it is not plugged into external power and then reinsert it, does the battery light come on again immediately the battery is reconnected?

Cheers,

Bill

tselling · #8 Post by **tselling** » Sun Aug 13, 2006 9:17 pm

The battery light comes on after about 5 seconds when I remove and reinsert it.

ka24det95 · #9 Post by **ka24det95** » Mon Sep 04, 2006 12:29 pm

I am having the same problem with my T40p any help would be great thanx

tselling · #10 Post by **tselling** » Mon Sep 04, 2006 10:04 pm

Sorry, I never found a solution. I decided to leave well enough alone since it seems to be working fine other than thinking its on AC-power.... and my grandfather tends to use it on AC only anyways.

ka24det95 · #11 Post by **ka24det95** » Mon Sep 04, 2006 11:05 pm

cool thanx

moonhead · #12 Post by **moonhead** » Sat Sep 20, 2008 1:06 am

bill bolton wrote:If you remove the battery while it is not plugged into external power and then reinsert it, does the battery light come on again immediately the battery is reconnected?

Cheers,

Bill

I've got the same problem, but if I remove the battery and reinsert it, the charging led does not turn on until the next turning on.

Any ideas?

Thinkpad T40 always thinks its on AC power. Any ideas?

Thinkpad T40 always thinks its on AC power. Any ideas?

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