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TR2/3/3A TR3/4 elec. temp gauge

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Jedi Knight
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My TR3 progect came with a Smiths 90-230 electric temp gauge,and sending untit in the thermostat housing.I realise this is not original and have no idea if it works,but would like to use it until I get the correct Lucas cap tube type.
I saw this dash on ebay and I am wondering what the device on the back of the temp gauge is,and if I need one.
Scroll down to back of temp gauge pic Ebay temp gauge .
Thanks
Tom
 
Did the 3 use a voltage deal like the 6 has. If it did, then that is a solid state version.

This is all hypothetical ,of course
 
The original gauge on a TR2-3B was mechanical, not electrical. TR4 onwards used electrical versions. That panel on eBay has one of the early TR4 electrical temp gauges installed (which is visually almost identical to the TR3 gauge), and the gizmo mounted on the back is called a "voltage stabilizer".

Unfortunately, that is not enough information to know if your gauge needs a "stabilizer" or not. Smiths made both kinds, generally their aftermarket gauges used balanced movements that did not require a stabilizer, while their OEM gauges needed the stabilizer.

Since you already have the gauge and stabilizer, probably the easiest way to find out is to hook it up without a stabilizer and see how it performs. If the needle moves up and down slowly, then it's probably the kind that needs a stabilizer. If it moves quickly (falls instantly to the bottom peg when power is removed) then it probably doesn't need the stabilizer.

Of course then you need to check accuracy anyway. Not all senders are the same (and some vendors don't seem to recognize that fact), plus the gauges themselve sometimes lose calibration. The voltmeter from my Stag (which is the same basic movement) was so loose inside that just rapping it on the bench would change its calibration.
 
Randal,thanks.I dont have a stabilizer on the Smiths that came in the car but will see what happens when I hook it up.
thanks
Tom
 
I put an electric type in my TR3 (rolling chassis) and the needle moved slow upon power up/down. Also it read very much higher than actual temperatures (needle pegged before the t-stat opened) until I added the voltage regulator. I have yet to check accuracy, but know it's closer than before since the meter shows the temperature climb at a normal rate to 185, then stops and hangs just a little past that (and I have a 190 t-stat).

Be sure to ground the instrument and the regulator.
 
Aloha Tom,

A quick way to check the gauge to see if it "works" is to use a 9V transistor radio battery to power it up. At 9V you won't harm the gauge. When voltage is applied the needle should move towards higher temps. As Randall said, if your temperature reading varies with engine speed you might need a voltage stabilizer. My experience is that at road speed the gauge would read very high, but at idle drop rapidly to very cool as generator output voltage changed. A non contact thermometer is a handy tool to see how the gauge compares to engine temps. Here is a relatively inexpensive one from Harbor Freight:

https://www.harborfreight.com/non-contact-laser-thermometer-96451.html
 
Texas ,Thanks for the additional info .
Dave ,Good tip on the 9v.I like high tech tools and have a bunch including infared gun.One is a Velocicalc TSI anenometer that I am makeing an adapter tube for so I can easily hold to carb and insert to measure velocity for tuning,kinda of a modern Unisync.
Thanks again
Tom
 
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