Otter switch - how did we get here ?

[mark rudder]

On a practical level, do we know the switching temps for Otter switches for motors using
88 deg & 82 deg thermostats? My radiator is currently being rebuilt & I'm changing to a 82
deg thermostat. The bloke is not happy with current mounting system, so while its out I
may as well put the correct temp range my 6B Cologne.

[willholderogri]

My fan kicks in at 82 degrees (I have a digital temp guage in my se5a

[scimjim]

Changing the stat won’t change the running temp (just the temp it’s fully open at) and the otter switch is the same for any stat. The otter switch is sited half way down the radiator, so the temp it sees is different to your gauge which is sensed almost at the stat input.

To run the engine at optimum temp, the stat and fan (in combination) should stop it going above 95 or below 85 (approx - measured at the stat), so an 82 deg stat should always be fully open once the engine is up to temp.

I think the otter switch hysteresis is something like 87/82 (on at 87, off at 82) - as measured halfway down the rad as mentioned.

[scimjim]

My fan kicks in at 82 degrees (I have a digital temp guage in my se5a

Where’s the sensor for your digital gauge sited? 82 at the stat is way too low.

[ScimmyMike]

According to Reliant WSM Jim it's on at 80 rising then off at 80 falling

[scimjim]

Unlikely to be 80/80 - it would be on and off every few seconds.

[willholderogri]

My fan kicks in at 82 degrees (I have a digital temp guage in my se5a

Where’s the sensor for your digital gauge sited? 82 at the stat is way too low.

that's 82 from the normal qauge sensor location on top of the inlet manifold

[scimjim]

My fan kicks in at 82 degrees (I have a digital temp guage in my se5a

Where’s the sensor for your digital gauge sited? 82 at the stat is way too low.

that's 82 from the normal qauge sensor location on top of the inlet manifold

that's too low - what temp does your engine run at then?

[AJL Electronics]

A hot engine is an efficient engine. Reducing the run temperature will give you knock on effects that are undesirable, including mixture control etc that have all been calibrated for normal temperature.

[willholderogri]

High 70 s I will have to check with my infra red thermomer

[scimjim]

Are you on LPG with a throttle body Will? Should definitely be around 90 at the stat for max efficiency.

[willholderogri]

On lpg with a mixer I will definitely have to check it .runs ok though