XPS 8900, Power button module

There are quite a few threads on here regarding the repair/replacement of the switch module in the XPS 8900, XPS 8700 and other Dell computers that use the same or similar modules.  The first step is to find out where the fault is.

Look at the XPS 8900 service manual and remove the top cover (page 64).

Clean out any dust/gunk and see whether the inner switch, not the top button, still works (the button can sometimes become displaced and not operate the switch properly).

If the inner switch is still working, then reassemble the button and top panel and see if this solves your problem.

If the switch is faulty, it is possible that you may be able to replace just the switch.  It is probably a standard switch that can be bought cheaply, maybe something like this.

https://www.ebay.co.uk/itm/Power-Supply-Reset-Switch-Button-On-Off-Cable-Cord-Connector-PC-Computer-UK/154379929914?hash=item23f1c2c93a:g:F1kAAOSwCWte0unc

I understand that the switch modules are now out of stock at Dell and buying a second hand unit from eBay ore elsewhere may give you a unit as worn out as your own.

If you need to replace the switch and can't find a direct replacement, then look for something like in the link below on eBay.  They are cheap and should be easy to fit, but will need the top hole opened up a little.  You'll also need to do some soldering.

https://www.ebay.co.uk/itm/12mm-Black-Power-Switch-Momentary-LED-Metal-12V-4Pin-Switch-Waterproof-Black/253826888749?var=553145917020

I hope that this helps.

@ak701169uk - Are those power button blinks in a pattern? That could be an error code.

When was the last time you replaced the motherboard battery? If it's old, I'd start there, before replacing the power button module. Don't know how much the CR2032 coin cell battery costs in UK, but it's ~US$2. Check Service Manual for instructions to replace it. If nothing else, you'll rule the battery out for not a lot of money.

BTW: Some users have had success spraying the innards of the power button with electrical contact cleaner. Just be careful not to let it drip on the other hardware or on plastic...

Re: Power switch often (50%) does not start the computer. The following procedure can start it: after pressing the button about 5 sec the switch light flashes.

another possibility is failing psu which makes power switch harder to start system. To rule that out test 8900 using another working 24/4 pin psu if available.

@ak701169uk  - Since @Jon-62 says there's a PSU LED and a BIST button on back of his XPS 8900, follow the instructions at the link I posted above to run the PSU BIST tests...

@RoHe   My XPS 8900 PSU has both a green LED and a small BIST button, but doesn't have a normal on/off switch.

@redxps630  That would have been my next suggestion if replacing the battery doesn't help...

The Service Manual doesn't say if this model has a PSU LED or a BIST button on the back, but the LED should it should be green when PC is plugged into the wall, if there is an LED with/without a BIST button.

Hvala za odgovor. Čudim se, da ugledna firma ne zagotavlja rezervnih delov in prisili kupce v zasilne rešitve. Lep pozdrav!

@ak701169uk Translate "Thanks for the reply. I am amazed that a reputable firm does not provide spare parts and forces customers into emergency solutions. Greetings!"

Dell will have provided spares of this component, but the computer is 4 generations old and spares have may have run out by now.

@Jon-62  I only reported what others have mentioned in this forum about using contact cleaner to which restore switch function. 

And we still don't know it really is the switch vs motherboard battery vs PSU...