Nissan Repair: Speedometer, odometer, and temp gauge problem, system checks, clean rag

Question

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I had the alternator and battery checked, both checked good. What should I check next, could it have anything to do with the speedometer sensor or cable? If so is there anyway to check it before replacing it?
Followup To

Question -
I have a 98 Frontier, this morning the speedometer seem to stick at about 45 MPH although I was sure that I was moving faster. As I slowed for a traffic light my odometer began flickering in out and my temp gauge began flucuating also. Everything now work fine if I'm over 30 MPH, but anything less it bounces like crazy. What do you think the problem is and how can I solve it.

Answer -
Eddie,

I think the alternator is going out.  Take the truck to Autozone or Checker and have them do a charging system check for free.  It could be a battery too.  So, have the system checked.

Answer
Eddie,

If the charging system checks ok then it is the cluster or the connection to the cluster.  Remove the instrument cluster and get a new number 2 pencil with the nice red eraser on the end.  Now, after you remove the cluster and disconnect the electrical connections use the eraser end to lightly scrub the electrical contacts.  If you want go to Radio Shack and get a spray can of tuner cleaner.  This is a light solvent and will heap to clean the connections.  Use very little and get a clean rag adn wipe the connections and put the instrument cluster back it and it should be fine for a few more years.  The initial installation lasted eight years so you are looking at about the same once things are clean.  The reason I say it is the cluster connection is that multiple gauges are screwing up.  If it were only the speedometer then I would say it was the speedometer sensor on the transmission.  But, since your temp gauge is messing up too it should be the connection.