Temp gauge restoration

[junkyardjeff]

I have a 37 GMC temp gauge that the tube has been cut off and can it be repaired,I do have a NOS 37 Chevy p/u temp gauge with a rusty face so could the two be combined to make one good gauge. The Chevy and GMC gauges are basicly the same but with a slight color difference,I am going with the GMC gauges in my Chevy since the GMC oil gauge goes much higher then the Chevy and I do have a later 235 in it that pegs the oil gauge and since the slight color difference I need to change them all so does anyone know a place that can repair or take the two and make one.

[Rusty_OToole]

Yes it is possible to repair. The tricky part is filling the bulb with ether. Then solder the tubes together with no leaks. There are instrument mechanics but you could do it yourself if you are handy and know how to solder.

[Friartuck]

"Temperature Gauge Guy"

172 Laurel Hill Dr.

South Burlington, VT 05403

(802) 862-6374

[Beltfed]

An important point may be missing here. The gauge and bulb (sender) are a matched pair just like the fuel gauge and sender. Mixing these parts could be tricky. As posted above, I would leave it to a pro as sender output data for various gauges is most likely slim pickings.

[junkyardjeff]

I am going to call that place and see what they can do,since the GMC gauges will be going in a Chevy it might be better to use the GMC face on my rusty and working NOS Chevy gauge.

[Friartuck]

Beltfed is correct. The bulb with tubing and the gauge need to be treated (calibrated) as a single pair. This article sums up the procedure nicely. You must use Ethel Alcohol as the solution and immerse the bulb into a ice water salt solution to lower the bulb's temp while the capillary tubing is soldered onto the gauge. Calibration is tricky and you must use Ethel and no other alcohol. You might need to use a small syringe to inject the Ethel into the tubing.

http://www.ply33.com/Repair/tempgauge

As for the faceplate, scan the original, touch up using a graphics program, print onto color laser paper (aka high quality photo) and adhere to the gauge. http://www.secondchancegarage.com/public2/faceplate.cfm

Tell us how this turned out. Post photos if you can.

[junkyardjeff]

I am not going to try to repair it,I will send it to someone who knows what they are doing.

[Gary_Ash]

The web page by Ply33 is correct, and note that he specifies the use of "ether", not alcohol. The particular ether is diethyl ether, the same stuff used as the original anesthetic and also for starting fluid. As long as there is a bulb of some type and size connected to a mechanical pressure gauge through a very small capillary tube, it will read the correct temperature. The Bourdon tube-type pressure gauge has its face calibrated in temperature, not pressure, and the calibration is not linear. A few points on the gauge face are enough to tell us if the engine is cold, warm, hot, or too hot. A vapor pressure temperature gauge works best when there is some fluid in the bulb and some evaporated/boiled vapor in the capillary tube and pressure gauge, e.g. about 100 °F to 230 °F for diethyl ether. If you are going to repair a gauge yourself, be sure to use a soldering iron, not a torch, so that it doesn't go boom!

Roy Martin, "The Temperature Gauge Guy" noted above, is the person to send the gauge to. He can supply new bulbs and tubes or re-attach an old bulb using a new tube, and he will check the calibration. He may send you elsewhere to have the gauge face restored.

Here is a table of the pressure in the capillary tube at various bulb temperatures. Note that these are absolute pressures, not "gauge pressure" :

Edited January 11, 2015 by Gary_Ash (see edit history)

[Guest MORRISGAUGE]

If your gauge has been cut, I highly recommend sending it in to have a new capillary line, thermowell and jam nut installed during rebuild. When you splice two used lines together, you open yourself up to a future break in the system. We see it too often here in the shop.

www.morrisgauge.com