speedometer on 2004 Chevrolet Trailblazer

The speedometer works fine for a while and then it slowly goes down to zero. What is strange is the cruise control works fine all the time. When I'm stopped at a stop sign, I hear a clicking.

Asked by for the 2004 Chevrolet Trailblazer
I had this problem as well the first thing that I did was to replace the speed sensor. This did not fix the problem the next thing that I did was to replace the instument cluster and this seems to have fixed the problem.

The reason that I mentioned the speed sensor is that replacing this component is much cheaper than replacing the insrument cluster. Speed sensor $28.00 Instrument cluster $320.00. I hope this helps you with your problem.
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This is very common on the 03-06 Trailblazers. The cause is the motors behind the gauges are failing, they all go out eventually. You can get it repaired here - and there's a DIY guide here -