06-17-2008, 08:10 AM
Been really have a time of it picking off all the little bugs on this boat. My latest efforts have been focused on the gauges. It would appear that the ones on my boat are mostly for looks. I've been having problems with them working on and off. My volt gauge will sometimes not work then all of a sudden be working fine. Yesterday the volt gauge was rock sollid but the temp gauge quit working. Then just before putting the boat away for the day it started working again. I've read a couple threads about poor grounding and believe this to be my problem. Anyone have any suggestions as to how this is fixed? Seems to be a weak area of construction on this boat. The old 95 Maristar I had may have been a bit more primitive but at least it had gauges you could count on for something. Thanks!
06-17-2008, 09:08 AM
It is a problem with the early 2000 boats. As you mentioned, the fix is to ground the MDC directly, your dealer should be able to provide you with the service bulletin; replace the MDC box; and as a last resort, replace the gauges with the later version (rev b or higher). For me, all my gauges including the tach, continued to fail after a new MDC. It wasn't until I replaced the oil pressure, temp and fuel gauges one at a time did I solve the problem. I haven't had a failure now in 5 years. Because of the multiplexing, one bad gauge can affect others in the system, so replacing one at a time, starting with the one that acts up most may save you from replacing all of them.
Supposedly the dealers have a diagnostic tool that will pinpoint the problem with system, although it didn't work in my case. Here is some good advice from JimN before you replace anything:
"Before you replace anything, remove the battery cables and do a few things- clean the cable clamps and terminals, disconnect the plug from the MDC box and make sure there isn't any corrosion on the terminals. If they are corroded, Tarn-Ex can remove it, then coat with dielectric grease. Then, measure the resistance from the battery negative to the MDC plug negative. You want to see no resistance but .1-.2 ohms will work. If it's a '99 or 2000 model, adding a heavier ground was recommended to fix this issue. Reattach the MDC plug and tighten the small bolt, but don't crank it too tight. Reattach the cable clamps and when the negative goes on (last), make it go on in one move, without tapping it repeatedly. These voltage spikes are one cause of this kind of failure."
06-18-2008, 10:39 AM
On my way to find some TarnX. I've checked the battery posts and connections, all very clean and tight. I'll be looking at the grounding behind the dash. This seemed to start happening when we installed the perfect pass. I will check the groung on the PP module and run a seperate ground directly to the module to make sure the problem isn't coming from the PP.