The Ace Answers "Mason" alarm for your engine temperature gauge.
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| It really helps to maintain ageing Townaces if you can spot, and deal with, the slightest signs of overheating. The temperature gauge which Toyota fitted is a very good one apart from one vital flaw. The sensor is well-placed (if inaccessible) in the cylinder head and produces a good variation of resistance over a useful temperature range. Experience shows that the temperature will normally be between 95 deg C and 105 deg C. The indicator gauge is easy to see but seems to assume that you do not need to know about temperature variation within a range of 90-110 deg C. | ||||||
 | This diagram shows its approximate response. 90 - 110 deg C is squeezed into two just "dots" on the dial. (Pre-new-shape Townaces have 20 dots across the gauge, new-shape ones have a solid line.) No wonder that needle sits reassuringly "just below the middle". Beware! If you wait to see it move you've probably waited too late. | |||||
  | Compare with these two commercially-available alternatives. 90 - 110 deg C occupies a quarter of the scale. Much better. See John Davies notes.The calibrated measurements of the temperature at the sensor are attractive but of dubious value. Don't underestimate the amount of work changing over the sensor in the head, fixing the indicator gauge in a suitable place, and running new wiring. And the driver will still only know about overheating if they are watching the gauge all the time. | |||||
 | This Gaugeplace Stepmaster Stealth gauge has just surfaced on the market in 2007 and deals with both the need for an expanded scale and an audible alarm. However bear in mind that it still requires you to install the sensor device somewhere in the colling system and devise a good place to mount the instrument, and then, as with any gauge, it will indicate the temperature at the place where you install the sensor. | |||||
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This diagram shows approximately the effect of the "Mason Alarm" added in a Townace. The sensor and instrument remain the standard Toyota ones - the sensor is in the head close to the gasket. 90 - 110 deg C is now spread over almost half the dial. Plus you have an audible alarm which you can set to get the driver's attention when the temperature exceeds what you choose as "normal".
You can fit this in less than an hour with one screwdriver. Fitting instructions. 6 screws release the instrument panel. The spade lugs on the 3 wires have to be slipped under three terminal screws on the back of the panel. The box can sit out of sight. - Dave Mason (designer & manufacturer), 27 April 2004, updated April 2007. | |||||