Speedometer

I have a 98 explorer XLT- V-8, all wheel drive. When I turn on the dash lights in about 5 or 10 minutes the speedometer stops working. Turn the dash lights off and in a little while the speedometer starts working again. I figure it is a thermal problem. Can anyone help, or do I get a new instrament cluster.

In the Taurus forum, there have been some people having issues with the flex board not making good connection to the connector. A thermal issue there (as you suggest) could lead to what you are experiencing. I'm not sure if your speedo in the '98 is cable driven or electric. If cable driven, your experienced would have to be coincidental, so it must be electronic. I think your thinking of a thermal issue is valid. Check the connection for the instrument cluster.

-Rod

I have checked that connection before with no change. I also noticed that if you close all to dash vents and max the AC it will revive the speedometer. Thats not always fun in december.

Is the speedometer the only item at the time that doesn't work, or does the fuel guage or tachometer also seem to be efffected? The speedometer solid state module gets its "hot with key in run" power feed from the same circuit as the other guages. Power comes into the instrument cluster on three separate wires, but they are all from the same circuit. The speedometer also appears to receive "hot at all times" power from a circuit that provides power to the speedometer solid state module in the cluster, and only the speedometer in the cluster. The vehicle speed sensor function is provided for the speedometer from the 4-wheel ABS computer. All instruments share a ground at the instrument cluster connector.

When the speedometer does not work, does the cruise control still work? If so, the vehicle speed signal must still be fine, but the speedometer is not displaying it, which it sounds like is what you suspect.

I'm not sure what the solid state module for the speedometer consists of, but that would be a suspect since you mention the connector checks out fine.

-Rod