Cookie Monster Posted July 31, 2016 Share Posted July 31, 2016 K series R300At Silverstone yesterday, in the traffic it nearly overheated.Turns out that the fan isn't kicking in which has always been reliable to date. Took the two terminals off and connected them and it runs fine so must be the thermo switch in the rad.Is this part a CC unique part or a standard motor factor part?Thanks Link to comment Share on other sites More sharing options...
SM25T Posted July 31, 2016 Share Posted July 31, 2016 Think it is a VW fan switch. Would also not open if air in header tank of radiator. Link to comment Share on other sites More sharing options...
SM25T Posted July 31, 2016 Share Posted July 31, 2016 Thanks to Andrew Revill .... Radiator Fan Thermoswitch Manufacturer: Bosch Typical Application: VW & Others Typical Part Numbers: 823-959-481D (77°C-82°C) 823-959-481E (70°C-75°C) 823-959-481F (87°C-92°C) 823-959-481A (87°C-92°C) Link to comment Share on other sites More sharing options...
SM25T Posted July 31, 2016 Share Posted July 31, 2016 Sure mine closes at 95C and opens at 85C ..... perhaps it is a 92-87 ? Link to comment Share on other sites More sharing options...
Paul Deslandes Posted July 31, 2016 Share Posted July 31, 2016 Unfortunately these thermostat switches are prone to failure as they don't like switching the fan motor on and off and the back emf burns the contacts. Apart from just changing it each time it fails (I got though three), wiring a relay into the circuit overcomes the problem and I've not had one fail for more than ten years since the mod. I'm pretty sure the topic was covered here a year or so ago so a search of the archives might show something up.Alternatively it might be possible to achieve the same result by wiring a suitable diode across the switch to snub the back emf spike but I haven't tried it so don't know if it works.Paul Link to comment Share on other sites More sharing options...
SM25T Posted July 31, 2016 Share Posted July 31, 2016 So .... local motor factors. If you remove yours it may have high and low values etched on it. Or phone Redline. Link to comment Share on other sites More sharing options...
seventh-heaven Posted July 31, 2016 Share Posted July 31, 2016 I had the same problem at Silverstone on satuday and ended up blowing the expansion cap top off. However mine was because of air in the top of the radiator which stops the fan switch seeing the true temp of the water - worth checking before you buy a new one!Topped up and bled the radiator and all was well with the fan switch - and thanks to Andrew Revill who drove me a cap down to Northampton this morning - top bloke!AndyH Link to comment Share on other sites More sharing options...
glasgow Posted August 1, 2016 Share Posted August 1, 2016 Unfortunately these thermostat switches are prone to failure as they don't like switching the fan motor on and off and the back emf burns the contacts. Apart from just changing it each time it fails (I got though three), wiring a relay into the circuit overcomes the problem and I've not had one fail for more than ten years since the mod. I'm pretty sure the topic was covered here a year or so ago so a search of the archives might show something up. No luck with search I can only find this http://www.lotus7.club/sites/default/files/images/Docs/Guides/Changing%20a%20radiator%20fan%20control%20switch%20to%20an%20ECU%20controlled%20fan%20with%20manual%20over%20ride%20switch-1.pdf which is not I am looking for. Anyone can post a guide to attaching a relay please. (And to complicate the matter I have a manual override switch that already has a relay. Hope this won't make adding another relay a complicated task). Regards Ahmed Link to comment Share on other sites More sharing options...
Paul Deslandes Posted August 1, 2016 Share Posted August 1, 2016 It's all in this thread. Replace the ecu connection with the thermostat, which also switches to ground.Paul Link to comment Share on other sites More sharing options...
Dobson_justin Posted August 2, 2016 Share Posted August 2, 2016 I toasted my fan switch at Cadwell, and just called redline who sent me a new one. Swapped over, bled the system thoroughly to get the air pocket out, and all fine again. Pretty straightforward. Link to comment Share on other sites More sharing options...
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