Join Date: Aug 2004
Location: Auckland, New Zealand
Re: Running temperature ?
CHF: Contrary to some comments here some of the early (pre 5/98 according to the workshop manual) 4 cylinder 156s DO have two sender units. Mine certainly does (mid 98 2.0TS), and according to the workshop manual so did the similar age 1.6 and 1.8. The later TS had the combined sensor on the thermostat.
I don't have any pictures, but it is easy to find. It is screwed into the gearbox end of the head, low down on the head towards the rear/inlet side of the head. Slightly above and behind the thermostat. There are two wires going to it, one is for the gauge temperature, the other is for the overheat light switch. Both of these earth through the block, so you can measure the resistance of each to car earth, one should be infinite (the overtemp switch), the other should be about 2500 ohms at 20deg, 500 ohms at 70deg, 350-400 at 80, 250-300 at 90. This is a no-cost way of checking what the sender is doing, if you also measure the ECU sender you can see if they agree. The ECU sender is different in that it earths through one of the wires, so you need to measure the resistance between the two terminals.
The combined sender on the later cars has three terminals, one is the gauge sender which earths to the block, the other two are for the ECU. They don't have an overtemp switch.