Q: My Tach doesn't read correctly sometimes. Power locks and wiper blades don't work all the time.

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Start the truck up and the tach will read 500 rpm most of the time when cruising (Truck sounds just fine). Power Locks on the doors, and the wiper blades dont work all the time. Sometimes when they dont work, I will turn the truck off then on then they work just fine.

My car has 130000 miles.
My car has an automatic transmission.

The problem with your tach sounds like it may be within the mechanical workings of the tachometer itself. If the gears that moves the needle around start to wear, you may have a bouncing needle or it can stop in one place. While the vehicle is hooked to a scan tool, you can watch the engine rpm on the scanner and if that reads 500 rpm as well as on the dash and the engine is definitely spinning faster, the sensor may be at fault. The power door locks and wiper problem may be separate problems as they don’t share many circuits. A loose ground connection can cause this type of problem as well as failing command switches or the relays that control these components. Consider hiring an experienced technician like one from YourMechanic who can come by for a closer look at the faulted electrical circuits to see where this bug is.

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