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MG Midget and Sprite Technical - Engine temp sender to temp gauge

Afternoon everyone. Perhaps a bit of an odd one this one, but someone has to ask stupid questions now that Prop has his car working!

Many moons ago when I was a young and utterly clueless whipper-snapper stripping down my car I couldn't figure out how to disconnect the temperature sensor wire from the back of the temperature gauge... so I snipped it off figuring I would jump the how to reconnect it hurdle if I ever got that far.

I have now reached said hurdle and realised that the reason I couldn't get it off was that it wasn't supposed to come off! Oops.

Any ideas on how to repair the cable/connection? Solder it? Or have I just plain knackered it?

Wee bit reluctant to dismantle the gauge as I once dismantled a speedo (out of curiosity) and all the internals went KABOOM and scattered everywhere never to be reassembled again!

And whilst I am asking questions... why is the wire so long and surrounded by another coiled wire thing?!

Thanks,
Malcolm
M Le Chevalier

Or is it not a cable at all and I am missing the point?! I thought the temp sender in the head had an electrical spade connection so assumed it was some sort of electrical cable but it is maybe a capillary tube type arrangement...

Malcolm
M Le Chevalier

hi malcolm,
im sure someone will be along with a definate answer but i think you have knackered it. i beleive that tube has some kind of gas or something in it.
regards bob.
bob taylor

What model MG?
MGA and earlier Temp gauges were operated by ETHER in a cappilary tube. If you cut the tube it dies. Can be repaired by qualified personell
Sandy
ss sanders

"but i think you have knackered it"

Yep - that just about sums it up :(

The bulb in the head and it's tube all the way to the gauge is filled with Ether - a liquid that boils at 34 degrees C and evaporates very quickly at normal room temperature. Once you cut the tube it is very difficult to fix - and fix safely! Ether is explosive.

Jim

J Smith

76 midget.

Badgered... oops. Oh well, time to build a ten gauge console.

Is a temperature gauge useful or is ignorance bliss?!

Malcolm
M Le Chevalier

It is possible to repair these gauges yourself. I did it successfully for my Bugeye. Searching on capillary gauge repair will provide multiple sites to show the process.

Basically, one sources a new, cheap gauge from ebay. These are used in a lot of 1930s to 1950s vehicles. Look for one with a high temp reading close to yours. The ends that screw into the radiator/head are pretty universal - check.

Put the bulb in a container of water, put in the whole unit in freezer. Make up a brass adapter with one end the diameter of your gauge tubing, the other the diameter of the new gauge tubing. Peel back the spiral spring to expose the inner tube. Remove the gauge from the freezer, quickly snip the tubing, reassemble to your gauge via the adapter and solder carefully.

Let thaw and check reading in boiling water. If not correct, you'll just have to note where boiling is on your gauge. My boiling point was right on, but the low temp reads a little high.

Or, buy a used one.

Jim
J Scott

Plenty on Ebay Malc - many old Brit heaps used similar. As for usefulness, deffo yes - as a good early warning of preventing possible engine doom if it starts to rise rapidly - more so if you do not have an electric fan.
Mark O

I belive you can use the lucas electical blue smoke replacement kit to refill the capillary tube... just use either instead of lucas smoke.... it does require a special fitting

Prop
Prop and the Blackhole Midget

This thread was discussed on 30/04/2014

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.