Ace Answers engine temperature alarm.
Fitting instructions, Estima.

If yours is an experimental/tinkering version, remove the lid, set the screw aside and use a rubber band to hold the lid on until you've finished tinkering. Notice how the cable can be disconnected inside the unit at the white push-on connector. Make a note of the switch settings or you will lose track of your tinkering!

To connect the alarm cable you must get access behind the instrument panel. You don't need to remove it or even disconnect anything. Just pull it out of the dash and turn it over to see the terminal screws behind the temperature gauge. Advice is available on the web. The best I can offer is as follows... (Models vary. Suggested improvements welcome. I own a Townace, not an Estima)

• Park where you can open both front doors and where you're not dazzled by the sun. Lower the steering wheel.
• Take the heater knobs off and prize out the section(s) in the middle associated with them.
• Undo the 2 screws under the section(s) just removed.
• The dash is in 3 bits but comes out as one long narrow strip.
• Start with the left- and right-hand ends. Lift the dash top so you can start pulling the front out.
• Once you see the first few plastic clips you'll see how the middle will come out. All the clips work the same way. Always pull back towards the rear of the car.
• Remove the four screws that you can see holding in the instrument panel. Don't drop them.
• Grasp the ends of the instrument panel, lift it slightly, pull the bottom edge towards you, notice that the top edge is hooked behind an obstruction.
• Keep pulling and lifting the bottom edge. Reach behind and keep the cables free from obstructions so that you can lift the bottom edge so far that the panel rolls right over as it comes free from being hooked at the top and you are looking at its back, upside down.
• The first time removing the dash should take no more than about 15 mins. When you put it back be sure to push it in far enough that the top edge goes behind the overhanging obstruction as you roll it the right way up.

Decide where you want the alarm box to be, thread the cable up behind the dash so it will end up in a suitable route when you've replaced the instrument panel. More access to it will be needed during initial adjustments.

Connect to the three terminals behind the temperature gauge as shown. Your alarm may have a brown cable with Yellow, Black and Red wires, or a black one with Blue, Green and Red wires. Refer to the correct illustration. Yellow or Blue (sensor connection) nearest the corner, Black or Green (0V) in the middle, Red (V+) is the third.

Turn the blue adjustment knob fully anticlockwise so that the alarm will sound at a relatively low temperature. When you switch on you should hear a quick blip from the alarm. Once the engine gets hot you will notice the gauge is reading differently. Don’t panic! The engine is almost certainly just the same, it’s the gauge that’s telling you something different. Whenever the alarm sounds turn the blue knob clockwise a small amount and it will stop. After a few trips you will find a setting where it only sounds occasionally, as a warning. If you want the alarm louder then take the cover off and make a small hole in it - having the box sealed protects what's inside but reduces the loudness a lot..

With a very hot engine don't be surprised if your gauge almost goes into the red. However DO NOT take the red line as an indication of safe/unsafe operating temperature. It's not that easy. The gauge now tells you about temperature changes, and permits some comparison between similar cars - but the indication will also be sensitive to manufacturing variations between engine sensors and the gauges themselves. You can easily and safely disconnect the alarm (one screw, pull off connector inside) if you want to be reminded how the gauge performed before.

Because I've been asked so many time I provide this calibration as the best I can do, but please don't take it as a highly accurate.
Before on the left, after fitting a Mason alarm on the right...calibration.

For "tinkering" refer to technical notes elsewhere, or just ask!

I am committed to correcting any faults, and making improvements, within the alarm unit, but cannot accept responsibility for how the alarm is used and therefore for the degree of protection it provides you.

Dave Mason, revised 12 March 2007.