We have same problem w/FL, though a later model. Some days both gauges work fine. Some days the tach hangs up & doesn't go above 1000 rpm. Some days the speedo hangs & shows only 20 mph @ max. Some days both gauges are dead.

Started acting like this a couple of yrs ago &  I figured something was on it's way out & would soon die exposing the culprit. Well, that hasn't happened yet, problems still occur routinely. I didn't realize it was such a common (relatively) problem in FL.