Every clock owner has heard that a clock needs periodic cleaning.
They call the shop and ask for my cleaning price. I explain to them that cleaning is only one of the steps taken in the repair of their clock.
As a clock ages dust particles and dry lubricants begin to wear out the pivots and bearings. Over time the bearings get worn enough to cause erratic timekeeping and sluggish chiming and the eventual stopping of the clock.
A proper and lasting repair is to polish the wear from the pivots and install new bearings where needed.
In our shop the clock is cleaned prior to and after the work is finished. We then lubricate with the proper oils and clock lubes and then we test it it for time and reliabilty.
Very few clocks can be repaired by cleaning alone.