Cooling fan switch S2

[maigret]

There was a small leak around the cooling fan switch and on fiddling with it, it just popped out. It appears to rely on friction of the grommet to hold it in place. I find that a bit risky on a hot pressurised system.

I would prefer to replace with a screwed in type but I need to know the cut in temperature. Anyone know what it is?

[lotusguy]

Hi,

The 'Otter' switch, (so named after the now defunct company which originally manufactured them), should open (turn fans off) at 82°C and close (turn fans on) at 92°C.

However, the 'Otter' switch should not just be inserted alone into the engine outlet pipe. It should be inserted into a rubber grommet and then further secured by a wrap of safety wire to prevent it popping out when the system pressurises. Safety wire (I prefer and use SS safety wire) can be purchased at minimal cost from any auto parts store. Once so secured, it is really a more than adequate arrangement. It sounds as if a PO replaced the 'Otter' at some point without replacing the safety wire. Hope this helps. Happy Motoring!...Jim'85TE

[maigret]

Thanks Jim

I'll put it back and secure it as suggested. I was lucky it stayed put.

It really needs a new grommet. I may be able to get one locally if they were used on other British cars.

Graeme

[lotusguy]

Graeme,

This 'Otter' switch was used on any number of older British cars. Usually a fairly easy part to find. The grommet often deteriorates before the switch itself wears out. If you can't find it, SJS, JAE or any of the usual Lotus parts sources can fix you up. Happy Motoring!...Jim'85TE

[maigret]

The local motor supply place (REPCO) can get me one overnight. We just identified the part from a picture in a catalogue they had. It was useful getting the temperature range as there were 2 that looked the same. Got one with 87/92 deg range.

[lotusguy]

Graeme,

I'm happy to hear you found something which will work. But I am somewhat concerned about the opening (fans off) temp of 87°C.

By narrowing the cyclic temperature range from 10°C to 5°C, the potential exists to either run hotter overall, or to have the fans come on much more often which accelerates the wear on the fan motors, relays etc.
I'd go ahead and try it, but be mindful of these potential issues and be prepared to switch to the Lotus part with the proper cyclic temperature range should either of them arise. Happy Motoring!...Jim'85TE