Trackpad button does not always respond

First check and see if the button is sticking up far enough - it should be almost 1/16" above the deck. If it's not, first try tightening the screws in the battery compartment and the ram compartment.

You can try the cleaning tip above, but get a can of electrical contact cleaner spray at radio shack. Don't use alcohol, use the correct chemical. Plus, it's pressurized and will blow a lot of gunk free.

If that doesn't work, follow the instructions for removing the top case (take a pile of baggies and stick the screws from each step in a baggie - mark the baggies "step 4", etc. if you want to keep track of all the screws). If you don't want to waste baggies by marking them, stick a scrap of labeled paper inside. Do the work on a soft piece of cloth that doesn't have a deep pile - dark is better (those screws are tiny).

When you get the top case off, you'll find 2 screws that hold the button in place. Remove those, and clean the button with contact cleaner spray (radio shack). The button will be attached to a flat plastic cable, so handle it carefully. Click the button as you clean it (it's tiny). Clean out the whole track button area with a can of compressed air. Replace the two screws and tighten them firmly. Re assemble the laptop. Should fix it unless the button is actually shot -in that case, you need a new top case assembly.

if your cleaning doesn't sort the problem it could be that the casing has distorted slightly, especially if the case as previously been removed to replace hard drive or any other hardware. In this case all I did was to place a piece of foam sticky tape onto the back of the mouse button. This holds the button up closer to the plate. This should allow the button to actuate against the plate. Worth trying before you order another top case - Worked for me!!