In 1998 I bought a Triumph Herald 13/60, here you can read about it's restoration and share in a few photo's from it's travels. Please feel free to leave comments to any of the posts, of even email me if you want to.

Wednesday, October 1, 2014

Two Temperature Sensors

One of the features of Megajolt is Advance Correction. This allows you to advance and retard the timing depending on the engine coolant temperature, adding a little advance when the engine is cold reduces the amount of choke needed and provides smoother running during warm up.

Like most cars of the era, the temperature sensor on a Herald is a single pin type that earths through the engine, Megajolt however needs the two pin type fitted to more modern cars. You can buy a two pin sensor that has the same thread as a standard Herald one (Part Nos. GTR185, ADU7161 & EAC3927), but then you'd have to do without a temperature gauge in the car, not ideal. I decided to buy one with a M10 thread that is already calibrated for Megajolt (see here).

The location of the Herald temperature sensor is at the top of the water pump housing, so ideally any additional sensor would need to be in the same area. After some thought I decided that I wanted the two pin sensor in this position and would mount the original on the opposite side of the housing.

Fortunately I had a spare housing, so I could easily see the best location both internally and externally. I took this down to a local retired engineer along with a sensor unit of each type. He drilled and tapped a 5/8" UNF hole to take the original sensor.

Original Sensor in its new location
He then drilled out the centre of an old single pin sensor, tapped an M10 thread so it could be used as a boss for the new twin connector sensor.

New two pin sensor in position
This view shows both sensors in position, the advantage of this set-up is that they will read a steady rise in temperature as opposed to fitting the other side of the thermostat, which reads cool then a more dramatic rise when the thermostat opens.

Both sensors in position
New sensor once housing back on the car
Original sensor in its new position
I really must thank Richard Baines for planting the seed to do this.

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