Universal Thermal Radiator Fan Switch & Adapter Kit

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0.21 KGS

The Stoney Racing Radiator Fan Thermal Switch & Adapter Kit allows you to thermally control any aftermarket universal radiator fan. Perfect for kit cars or older vehicles that don't use electric fans as standard.

The switch actives when the sensor reaches the "on" temperature and turns off when it drops back below the "off" temperature. With seven different temperature ranges available and adapter sizes to fit radiator hose I.D.'s from 26mm up to 40mm our kits provide an easy fan switch fitting solution for the majority of vehicles.

The kit includes a pair of good quality fully stainless steel clamps, with no perforations in the band and featuring a rolled edge, suitable for all rubber and silicone hoses.

Ideal for use with our range of high powered fans featuring sizes from 7" to 16" and motors from 80W to 160W.

What Switch Temperature Do I Need?

This varies from vehicle to vehicle and colder is not necessarily better as the ideal operating temperature range for an engine may be higher than our lowest switch range would allow it to reach.

If possible you should find out the ideal operating temperature of your vehicle and choose a switch that turns on around 5deg. C higher than this ideal operating temperature.

If you cannot find your vehicle's ideal operating temperature you can also estimate by the vehicles thermostat temperature. In most cases the on temperature of the switch should be around 10°C to 15°C higher than the vehicles rated thermostat opening temperature (the temp the thermostat begins to open at).

So for example if your thermostat starts opening at 74°C you want an "on" temp of 84°C to 89°C so you would use the 85°C on switch. If your thermostat opens at 82°C you want an "on" temp of 92°C to 97°C so you would use the 95°C on switch.

Thermal switches available:

  • 80°C (176°F) on / 72°C (162°F) off (± 2°C)
  • 85°C (185°F) on / 77°C (171°F) off (± 2°C)
  • 90°C (194°F) on / 80°C (176°F) off (± 2°C)
  • 95°C (203°F) on / 85°C (185°F) off (± 2°C)
  • 100°C (212°F) on / 90°C (194°F) off (± 2°C)
  • 105°C (221°F) on / 95°C (203°F) off (± 2°C)
  • 110°C (230°F) on / 100°C (212°F) off (± 2°C)

What Size Adapter Do I Need?

To determine what size adapter you need simply measure the inner diameter of your top radiator hose and choose the matching size from our store. The adapter will fit hoses 1mm smaller than it so a 30mm adapter can be used for hoses 29mm-30mm I.D. for example.

Some top radiator hoses are larger at one end than the main body of the hose so if this is the case for your vehicle take care to measure the end that is the same diameter as the part you will cut to fit the adapter.

Available in adapter sizes 26mm, 28mm, 30mm, 32mm, 34mm, 36mm, 38mm and 40mm O.D.


Important: The switch must be installed in the low current side of a relay (i.e. one of the wires to pins 85/86 on a standard 4 or 5pin relay). If the current exceeds 1 Amp the switch is likely to fail and this is not covered under warranty. Using the switch directly in the wiring to a fan will cause the switch to fail.

To fit simply cut your hot radiator hose (usually the upper one) at a straight section into two pieces using a stanley knife, using a hose clamp lightly tightened around the hose as a cutting guide. Remove approx 30mm length of hose from one of the cut halves which the adapter will replace. Rejoin the two sections with our adapter and the clamps provided and refit the hose.

For wiring we recommend running the fan directly from the battery via a relay and inline fuse, with the relay activated from a 12v + switched ignition source. You can also use a constant 12v source to activate the relay instead and this will allow the fans to continue running after the car is turned off until the coolant has reached the "off" temperature of the switch, as many modern cars do to aid with engine cooling after running.

The switch should be wired into the ground wire for the low current side of the relay. The maximum current rating of the switch is 1 Amp so fitting any fan inline with the switch will cause it to fail.


  • Fitment: Universal 12V
  • Construction: Hose Adapter - Aluminium, Thermal Switch - Brass + Plastic, Hose Clamps - Stainless Steel
  • Max Current Rating: 1 Amp
  • Max Operating Pressure: >5bar
  • Operating Temperature range: -30°c to 200°c
  • Warranty: 1 Year (UK based)

12 Reviews Hide Reviews Show Reviews

  • 5
    Radiator fan and adapter switch and adapter kit

    Posted by Tony Clarke on 12th Aug 2022

    An easy fit for my Discovery, wish everything was this easy

  • 5

    Posted by woodymay@hotmail.co.uk on 22nd Jul 2022

    It works perfectly for a reasonable price, I would buy it again.

  • 5
    universal fan switch

    Posted by jay on 27th Jun 2022

    this i fitted onto a pre 98 mercedes v6 2.4 as the engine always got too hot during stationary traffic even with a good rad good water pump and lower opening thermoststat fitted in 1 hr and works far better than the original thermo switch the car nows sits in stationary traffic without overheating and gauge stays in normal range good fitting works well simple to fit even for a non mechanic like myself

  • 5
    fan switch adapter

    Posted by trevor fox on 26th May 2022

    i managed to fit this in the very limited space on a TR3A using some 38mm hump hose at one end to allow for movement. far better than using capillary switches or fitting to the bottom hose. a great piece of kit.

  • 5
    Worked great for MGB GT

    Posted by Ted Smith on 21st Jan 2022

    Bought this to replace some customisation my dad had made to the top hose of MGB GT. great help from the company pre purchase and it worked great. No leaks. No extra parts needed.