Saturday, June 15, 2013

Dodge Ram 350 Van Speedometer Goes Wild

Speedometer Runs Erratic

Q: 1994 Dodge Ram 350 Van. Speedometer occasionally goes wild--0 to 60 mph back and forth. then quits to 0 for an hour.

Fuel guage does not work.

A: Most probably the problem is Speed sensor or its issue with instrument cluster.The vehicle speed sensor is the most likely cause for this problem. The vehicle speed sensor is in the left rear of the transmission, hopefully this is the sensor that you have to replace. The one on the top of the rear differential is only used for ABS on these older vans.Please make sure you replace the correct sensor.

If the correct sensor is replaced and the symptoms are the same then you almost surely have a wiring problem. The sensor receives an 8v reference, a sensor ground, and has a signal wire. While it's acting up you would need to start by testing at the sensor to check the reference voltage, sensor ground and the pullup voltage on the signal wire. You should find at least one of these is missing. I would recommend at least a good visual inspection of the wiring leaving the sensor and running up to the engine compartment.

The fuel gauge could either be the fuel sender or wiring, assuming the gauge in the replacement cluster is good. Outside of a visual wiring inspection you would need to drop the fuel tank and check the sender's pullup voltage and sensor ground, if they are ok then you know the problem is the sender.

This will help.

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