I have the same problem on my elevator trim indicator and asked the Ray
Allen Company (new name for the MAC product line) people at their booth
at OSH last week about the problem.  They said to send it back and they
would fix/replace.  It seems that early on they had some parts that were
not up to snuff (tech term I think).  Mine indicator was purchased about
four years ago and has about 500 hours on it.  

Their new address is 2525-8 Pioneer Avenue, Vista, CA  92081  Phone 760
599-4720.  Web site is www.rayallencompany.com