Author Topic: Repairing mechanical temp gauge  (Read 321 times)

Offline jeff10049

Repairing mechanical temp gauge
« on: October 08, 2017, 11:53:14 PM »
If you have ever come across a temp gauge where the tube got cut off or broken they can be fixed easily.
A mechanical temp gauge is just a pressure gauge certain liquids have a specific vapor pressure to temp curve just change the pressure numbers to temp and you have a temp gauge.
The working fluid of most automotive temp gauges is dimethyl either. That's whats in the bulb at the end of the tube.

This gauge is for a 50 chev pick up that I have started restoring where some asshat cut all the original gauge tubes and wires off and had some stupid cheap shit ones hanging under the dash.

In this case there was some remaining tube on the back of the temp gauge I tested the gauge with a blow gun over the tube it moved freely.

What I do is go buy the cheapest mechanical temp guage you can put the bulb in an ice bath or better dry ice to cool and condense the either this will keep it from evaporating when you cut the tube.

I like to use a slightly larger 1/8" copper oil pressure gauge type line to make a splice. solder a piece of this over the existing stub.

Next tin the new line with solder before cutting to minimise the time the line is open. Cut the line make sure not to pinch it shut or reopen it with a pick tool.

solder this into the splice and you have a repaired gauge I use a weller electric soldering iron for the work. its just like copper house plumbing on a small scale.

Don't overdo the solder or it may plug your line. Also, avoid open flame soldering either is very flammable

Offline jeff10049

Re: Repairing mechanical temp gauge
« Reply #1 on: October 08, 2017, 11:56:20 PM »
as soon as the test water boiled the gauge was 212 close enough for me

Offline MiniDave

Re: Repairing mechanical temp gauge
« Reply #2 on: October 09, 2017, 06:48:24 AM »
I had read about people repairing these mechanical gauges, but I didn't know the trick of super cooling the ether - great tip! And well done for fixing the original gauge instead of buying replacement or aftermarkets.

Fix it, don't replace it.
1989 Cooper Racing Green
2009 Clubman S
1969 Jaguar XK-E FHC
2004 Audi Allroad 2.7 TT