It appears that this forum has essentially died, but I want to share recent experience concerning Subaru speedometer issues. May help.
Son has 1999 Outback with same intermittent speedo issues. Also there was other evidence of electrical issues in the car (warning buzzer was weak, radio worked sometimes, etc). We took instrument cluster out of car and tested voltage being received at the back of the 5-pin connector. Voltage started high but declined as car accelerated which we assumed was normal as speed was working. We removed speedo head from cluster and connected back to 5-pin connector again measuring voltage on each side of the connection. There is where we noticed discrepancy. Voltage would drop occasionally when car was not running. We removed female of 5-pin connector and resoldered connections. Now we have stable voltage on both sides of the connector. We also removed oxidation from screws holding head in the cluster as it appeared that provided grounding to entire cluster. After reconnecting all of the couplers to the back of the cluster speedo works well and has consistently. Also removed other electrical issues with interior. Bad thing now is that odometer records mileage twice as fast. Not sure what to do.
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