Odometer non-operational

[Matt Suffern]

Hi all,

My odometer quit working about a month ago.  It's stuck at 98999.  Before it stopped working I pulled the cluster to replace one of the lights and 
was very careful to plug everything back in before reinstallation, including the speedo drive cable.  A couple of months later the odo crapped out.  
Everything else in the cluster works just fine--all gauges and indicators.  I pulled the cluster again this past weekend to try to discover if there 
was something amiss, and everything is plugged in and tightened down.

Is the odometer electrically driven?  If so, could the ground be bad/marginal and not supplying enough juice for the odo to turn over all the 
tumblers necessary to make it to 99K?  And if so, which ring terminal on the back of the cluster is the odometer motor's ground?  That's my only 
theory so far.

Any BTDTs would be most helpful.  It'd be really nice to do more than guess at how long I have before the next oil change.

Thanks guys.

Matt
'86 4kq
'72 240Z
Chapel Hill, NC