Engine metal temp alarm - an ebay special aquarium 12V jobbie
Much credit to Gannon (fka Suparoo) who pointed out the existance of these units and suggesting the bullet shaped sensor would crimp nicely in an electrical eye terminal. I used two sizes of terminals whose wire end fitted into the larger one, chopped off the ring of the smaller one, soldered 2 together, drilled out hole to 4.0mm and slowly carefully jammed the sensor inside
http://www.ebay.com.au/sch/i.html?_saca ... +12V&rt=nc
pretty easy to wire up once you fiddle with them and reread the Chinglish a few too many times. The sensor wires are not polarity fussy, nor is the power/earth supply ( or I was lucky first try ) I hear a relay click inside but no power is switched across its switching terminals, so I linked or bridged power from its power input terminal and across to the switched pair of which output then went to a little $3.95 jaycar piezo screamer, now mounted in a 22mm hole in the back terminal cover
Unknown as yet whether the plastics will withstand our Aussie sun. The orange plastic clips at its rear were sitting in the sun inside the cabin for a few months and they have lost some colour
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The cavity is packed with car wash sponge to help the speakers (i think it helps!)
OK and results are off the hole tapped into the top of the EA81 turbo side head (just no turbo

) , location gave same results as thermostat bolt on my EA82T so not too fussed as to its location....... EDIT>> now wondering if the head is a bit too hot to give an accurate indication of water temp.
These units show that the metal warms up before the water does - hence the early warning for engine overheat! Might try thermostat bolt and see if any change
Idled it until the RHS fan cut in at 98 C ! which was just a mm short of 3/4 on the Brumby gauge, same fan cut out at 92C - a mm above half mark.
Manually switched both fans until they pulled temp down to 75C and gauge was ~ mm above 1/4
It is interesting to see the numbers compared to the gauge, noting 95C seems to be the opening temp of most of our thermostats available. Think mine in there is 71C (or 171F)
Getting too
hot there for the heatshrink on the sensor, its melting !!
Placement would have been better if I'd been thinking of the passenger inflight entertainment - and the 5th gear position

, but that is why I have the alarm , and set at 90C like with my EA82T