"Sticky" Auto Throttle Button - Repaired
Wednesday, November 30, 2011 at 9:12PM 
I noticed soon after the TQ arrived that the engine number one auto throttle button was a bit “sticky”. Depressing the button, it would stay pressed in for a few seconds even though pressure had been released. The A/T buttons are one-way buttons meaning that they are click buttons – click in, release, and click out. It’s probable that after many hours of service, sweat, dead skin cells and dirt has built up on the inner button behind the spring mechanism; a friend suggested that DNA analysis of the built up debris would probably provide a list of suspect pilots!
Whilst the button was still in place, I attempted to loosen the built up material using a can of pressurised electronic cleaner fluid. The fluid, I hoped would dislodge any loose material before evaporating. Unfortunately, this didn’t work in the long run, although once lubricated with the evaporative solvent, the button operated correctly for a short time.
Circlip
The button is held in place within the throttle handle by a ½ inch circlip. Beneath the circlip and button there is a spring mechanism that pushes the button out after being depressed. Using a pair of specialised circlip pliers, I very carefully removed the circlip making sure that the spring mechanism of the circlip didn’t propel my A/T button out the window and into the garden!
With the circlip removed, the inner portion of the throttle handle slides out revealing the button and attached wiring. The button is a modular design (shaped to fit inside the thorottle handle) and unfortunately cannot be disassembled further, Therefore, I reassembled the button and sprayed a small amount of silicone spray around the button, allowing the silicone solution to penetrate around the the edge of the button.
The silicon lubricant (which is non conductive, so there is no issue with power shorting) seems to have solved the problem as the button no longer sticks, however, this is only an interim solution. I'll search for a replacement button module. Sometimes the most simple solution will fix your problem!!
No doubt I can purchase a new replacement from Boeing for errr $800.00.... I think not. Eventually I'll find a disused button module in my travels. If you find a B737 on the line and note the captain side A/T button has been removed - you know who "stole" it :)
Reader Comments (2)
Does it need to be the captain's side button?
HI Eric: Actually I don't think it matters. Both AT buttons appear look identical. In theory, you should be able to change the FO with Capt and vice versa. Best, Iain