Microswitch sticking will start, but stop as soon as foot off the red switch lever

did you run out of water ???

here is dc18 foot repair video

http://ww.ebay.com/gds/REPLACING-THE-POWER-SWITCH-ON-ANY-KIRBY-G-SERIES-VACUUM-/10000000003752018/g.html

first you need to remove the top cover before you take the three corner screws out of the bottom. Remove handle, bag , two screws on the scuff plate and stick a flat head in the slot of the scuff plate and pry up. you will have two screws under there and two screws in the front and the top cover will come off. lift up on the plastic foot pedal and it will pop off the transmission. you can now remove the belt off the transmission by taking the three screws out on the bottom. there will be a little metal lever that is splined like the shaft of the foot pedal. that lever needs to be in the proper position for the foot pedal to shift the transmission.

The problem is likely caused by either (a) a broken or worn microswitch operating lever or (b) a faultyt microswitch. With the bin removed, the lever becomes visible just above the filter upon which the base of the bin normally rests.

Replacement of either part necessitates dismantling the appliance. The necessary parts are available from http://www.espares.co.uk/parts/dyson/dc04-zorbster/p/1086/716/4/420621

- Look for the reset button on the side of the brushbar housing - there should be a red sticker and a red button. Push it once. It's
not gonna stay depressed, it's gonna pop right out - that's normal.
- Step on the red pedal on the back
- Turn the machine on with the red power button
- Press the gray button next to the red power button - this is the ON/OFF switch for the brushbar - if it doesn't spin, press and hold the gray button down for 10 seconds
- If it still isn't spinning, remove the brushbar and make sure nothing is blocking it and withholding it from spinning
- For further troubleshooting assistance call the Dyson helpline, they know what they're doing

I had a problem with my switch not working. The cheesy microswitch has a little nub on the back that breaks off. They kind of work like a ball point pen. I noticed that if I held my thumb against the back of the microswitch, it would click on and off.

Disassembly:
First, unplug the machine and disassemble the switch housing. There is a screw in the front. It takes a no. 10 Torx driver to remove it.
On the back there appears to be two little tabs that need to be pulled out. Don't mess with them! They are there to fool you. Instead, with a flat tip screwdriver, reach down past the tabs and pry inward (the handle of the screwdriver moves outward, the tip prys inward).
On the front is a little tab that needs to be gently pryed down. The unit should slide out.
With your thumb against the back of the switch, press the button. If it seems to be staying down on one stroke and popping up on the next, continue reading. Otherwise, you may need a new switch.

Now for the fix/jury rig:
With the plastic housing set aside. Put all the wiring and switch in it's place on the vacuum. The switch has grooves that allow it to slide onto the vacuum. Everything should go in neatly.
What you need is a thin piece of wood or plastic, about 3/4" long and 1/2" wide (a popsicle stick would probably work). Slide it between the bottom of the switch and the molded plastic on the vacuum. Make sure it is snug. Try the switch. It should be working now.

Now carefully slide the housing back on. I like to depress the switch first. Make sure the housing snaps back on. It takes a bit of force, but it should slide fairly easily right up to near the vacuum's face. If not you may want to make sure you're not interferring with any wires etc.

Good luck,
bentod

If was foxed by that one too. There is a microswitch or device that detects it the unit is upright - it inhibits the roller motor.
Soon as you lower the arm the rollers go around.....if not then it must be a fault.

bad switch

Mine did a similar thing. I kept trying to use it anyway, when it made a violent jerk (I thought it had broken something) and it started to work again.

Have you tried pressing both buttons at the same time to make it go straight ahead? It might work.