Short sweep electric pressure/temperature gauge reads high or pegs.

Short sweep electric pressure/temperature gauge reads high or pegs.

This FAQ pertains to short sweep, electric gauges, that use a single-terminal sender. The symptom is that the gauge will either immediately peg at full reading, or may gradually read higher and higher until maxed out, and appears to get there rather quickly. An example would be starting your engine cold, and having a reading or 180 degrees in under a minute, then having it continue to rise.

For this problem, let’s take a look at the ground you are using at the gauge. This is not related to sender ground. If you have already verified, or even tried another ground, then take a closer look at the ground terminal on the back of the gauge. These terminals are held on by two things. A peaned-over plastic stake, and a meter nut. If the meter nut (which is actually there to create contact from the terminal to the internal meter) is loose or missing, then no matter how good the ground is to the ground terminal, that ground will never make it to the internal meter.

No ground, or poor ground will cause anything from a higher than actual reading, to a pegged reading as soon as power is turned on, and with the sender circuit hooked up.

The solution is to tighten the nut (assuming that it is still there), or you may obtain a replacement nut, which is M4 x 0.7 thread size.