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Faulty Gauges?

I have a 2004 Ford Focus SE, with 39122 miles of driving. Recently the temerature gauge and gas gauge have been returning to center position when I turn off the ignition. Needles fall to inactive position when car is turned off but within 1-3 seconds jump up to center of gauge. All gauges are working properly (gas, speed temp. etc) when car is running. I maintain a regular oil and maintance schedule and recently had a transmission flush and injector cleaning as scheduled. Anyone have any idea what could cause this, will battery be affected?

This sounds to me like it may cause a very small parasitic drain, but it’s unlikely to be significant enough to cause a problem.

These gages use what’s call “DeArsenval” movements. They’re basically just an armature with a permanent magnet being moved by a small amount of current flow through surrounding windings. They’re returned to zero by a small coiled spring. You may have a very small amount of current flowing through them when the key is “off”. I honestly wouldn’t worry unless you begin to have weak-battery symptoms in the morning. Others may disagree, but troublehsooting this will be a pain and repairing it even more of a pain.

To troubleshoot it you’ll need to remove the instrument cluster, get a schematic, and measure for current when the vehicle is off. Since this is likely using a ribbon wiring harness, you’ll need pin probes and the correct color codes.

If I’m right, then repairing it will involve replacing the key cylinder (blah!). Of course if the cylinder is on the ground side of the circuit, you may have a high-resistance short to ground in the circuits and troubleshooting gets even tougher.

Of course others may have other theories that I haven’t thought of.

It appears something is suppling power to the gauges somehow. Perhaps a bad blocking diode may be the cause, just a guess. This will cause a drain on the battery but I can’t say how much. You could have a shop measure the current draw on the battery to see how much extra current is being drawn. Normal current draw should be around 25 milliamps.