BB512 Radiator fan switch

I don´t know when this switch will shut on, sorry.

the thread of this switch is M 22x1,5, and those switches are in nearly all european cars from this area. go to a local distrbutor for car parts and have a look if you could find a switch with lower switch on temperature. for example VW or AUDI has it.

but when the temp is 105 ° C at the gauge ( you are sure that this is the right temperature?? ) and the inlet hose is only 89°C then I think you have a problem with the waterpump or with the radiator let not enough water through. but when you meassure the temperature at the hose outside it is about 2-4 ° less then inside

I put in my BB a switch with 77° C to switch on and to switch off at 73°C

 

See page 73 in your OM (when coolant temp reaches 84 deg C = fans on; when coolant temp falls to 75 deg C = fans off).

The water temp gauge in the cabin is driven by a thermister mounted where the hot coolant exits the cylinder heads (item 6 here: http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=3477) -- check the temperature of that casting (item 5) with your Pyrometer too. That casting should be at about the same temperature as the inlet to the radiator if the thermostat is working correctly (although not sure how you can really be sure about the emissivitiy of each surface you are measuring).

Or the thermostat is not closing completely/well - which would let hot coolant just recirculate in the engine without ever going to the radiator (assuming that it's not just the gauge being a little inaccurate).

 

For what it's worth, I just took my BBi on a 500 mile round trip last weekend. The temperature stayed between just under and just over 90 degrees C.

 

my fans kick on at 90 degrees C - all three are wired to come on at the same time