Heat Gauge all over the place

Air in system, bad thermostat, or headgasket going out.

Assuming you have made sure there's plenty of coolant in the radiator.

Pull the do no remove cap and look, add 50-50 mix, check again once it's cooled down again. Coolant should always be all way to cap.

Make sure the rad cap and tubing to the overflow bottle is good.

Saw this problem in an 88' Tempo with the 2.3 HSC engine. The radiator kept burping antifreeze and the temp gauge was erratic. I don't recall if the heater was acting up because it wasn't cold enough to be using it at that time of year. It turned out to be the head gasket.

We had a 91 Ford ranger in the shop Thursday that was doing this.He was also complaining of no heat.But the Rad. tank was 1/2 way low too. I pressure checked it, and found no leaks. The motor was warmed up,but the temp gauge was way way down almost to the bottom "peg" I suspected a missing or stuck open T-Stat, as a start. We put in a new T-stat and flushed the system out, and refilled it, but it was still the same. Driving up the road, the heat was fine, but as soon as you come to a stop light, it would blow cold. We now suspect a head gasket . NAPA sells a test kit, it don't cost too much, that you fill with a test liquid, and place over the rad. filler neck (motor running) and pump up air into. If the test liquid stays the same color, you are OK, if it turns "piss yellow" you have a issue. Tony

You obviously do not know how to diagnose the problem, why don't you take the car to somebody who can before you cause engine damage?

mike