After a couple of months of owning my Elise, the temperature reading on the STACK unit became erratic - switching on different electrical systems in the car was causing the temperature to climb higher and higher. This turned out to be a poor earth connection to the chassis, caused by slight corrosion. It's a relatively easy fix, which involves removing the earth strap and cleaning the connection points.
1. Ensure the battery/immobiliser
is disarmed (follow instruction in user manual for battery removal).
2. Remove the water washer bottle from the car - it just slots into place.
3. Loosen the nut securing the negative strap to the negative side of the battery, and pull the strap off.
4. Repeat this procedure with the positive side.
5. Undo the three bolts securing the battery bracket in place, and remove the bracket.
6. Slide the battery towards the rear of the compartment - this will allow you access to the earth-strap connecting.
7. Find the strap connection to the chassis, and undo the bolt holding it in place. Be careful not to drop any washers!
8. Remove the strap from the car.
9. Clean all connections with fine grade abrasive paper, including the connectors on the battery end, the battery terminals and the area on the chassis where the strap connects to.
10. Refit all connections by following the above instructions in reverse order.
11. Once all connections have be tightened, smother all electrical connections with petroleum jelly to prevent future corrosion.
Check the accuracy of the gauge by running the engine to normal level and switching on the electrical systems - hopefully the gauge should remain unaffected by the switching of the different systems.
Front earth strap
Rear earth terminal
Questions? Email me.