39 Temp Gauge Calibration
 

I have a very nice original temp gauge. My problem is that at room temperature, the gauge reads about 100 F. With the bulb in boiling water, the gauge goes off the scale and out of sight. Is there any way to calibrate them?

Re: 39 Temp Gauge Calibration
 

I believe most gauges staqrt at 100deg's? I would carefully warm up a pan of water to 170 degrees checking it with a separate temperature gauge ( maybe a meat thermometer?). Your car gauge should read about at the center when the (engine) sender is at this temp.

Re: 39 Temp Gauge Calibration
 

Sounds like it has an 'air bubble' in the tube. Try turning it upside down and gently shake it some.

Re: 39 Temp Gauge Calibration
 

The metal (scale) part of the gauge snaps around the thermometer tube are you able to move it up or down? Mayby bumped from proper position,otherwise I aggree with an air bubble somewhere in the line. This sounds crazy but I have done it,centrifugal force is the cure,carefully attach strong string like clothesline to upper gauge part,mayby hold on with duct tape and swing it around in a circle above your head or whatever,it will work.

Re: 39 Temp Gauge Calibration
 

Bruce, Improper storage of a gage removed from a car will form air bubbles inside. (The head should always be higher than the sender.) I've tried several methods to remove the bubbles, and have found 37 Coupe's centrifical force method to be effective.

Look at the gage glass closely, and you will see a fine scratch on the glass. This is the factory calibration mark indicating 212º F. When you have removed all air bubbles, test the unit with boiling water to confirm calibration. Install with that mark opposite the 212º mark on the indacator.

Re: 39 Temp Gauge Calibration
 

Update:

As you guys suggested, there was an air bubble trapped in the cooper tube/bulb. I hung the gauge with head higher than bulb for about a day, then cycled the bulb from hot to cold water three times and low and behold, a bubble appeared in the head. At that point, the gauge settled in at exactly 212 when the bulb was held in boiling water. The OEM gauge is a nice bright red too. My old one was a repro and the fluid in the head was nearly clear and hard to see. Thanks for the suggestions!