IF you have a Freightliner chassis
. In 2000 FTL used the Medallion System III gauges. Information for the gauges is supplied by the VDC (Vehicle Data Computer) Poor solder connections to the air pressure transducers in the VDC did cause gauge problems. I had a 2000 GeorgieBoy DP, indications at various times were speedometer or air pressure gauge going to zero. (Cruise control still worked/ no alarms or lights)
A service bulletin is available here on IRV2 to troubleshoot the gauges.
The VDC solder repair is discussed here. http://www.irv2.com/forums/downloads.php?do=file&id=76
Both articles are in the files section of IRV2 and can be downloaded.
Note: The VDC was put in various locations by the RV manufacturers, mine was in a rear compartment on the passenger side, along with the ECM, Transmission module and VIM. You can see the air lines coming into the VDC..
Hope this helps.