MKIV part list for radiator fan switch

[jbottini]

There certianly is a thermostat FF..I checked it when can was running 10* F warm...solved it by topping the overfow tank. The 302 is rather cold hearted, but should reah operating temp within 5-10 km( still in Italy). You might take thermostat out and put in water on stove with a thermometer and see when it is opening / closing though. I never checked it for range or operation myself

[Flyinghorse]

If the fan cuts in very early then it could be because its hot were the fan sensor sits,or its out of calibration.
   I would check fan sensor/switch as well for operating spec. Is the fan switch at the top of the system?
   
   The 302 water pump can have a bypass system in the water pump for heater & faster warmup (mine does) so you should be able to tell if thermostat is working by holding your hand on the hose as the car warms up. It will suddenly get hot when the stat opens. Till that point your rad fan stat should see no hot water unless something is badly amiss:
   Air lock
   Faulty switches
   Thermostat issue easy to put in missalligned,does it have an equalizing /jiggle valve at the top
   
   The temperature gauge sensor is high up on the block near the distributor (on my car). I opened mine slightly to ensure there was no air below it. I also had a hose at the top of the radiator that I used to bleed everything.
   The Temp sensor is not very clever and cheap,and the temp gauge (on the CRS) very poor range. The whole measuring system is electrical.
   How linear it is is questionable & It could also be tested.
   Graham

[westcott]

Here is my answer for a replacement radiator fan switch used in our MK IVs.
   
   My one let me alone after the first engine start this year and i went hunting for donor car and part.
   
   Finally i ordered a switch which is exactly the same but different number on it.
   
   The MK IV switch is a Otter switch # 5802082
   
   The switch i found with the same dimensions and switching temperatures is out of a MGB from 1979 on with # 6800057A, maybe other switch manufaturers have different part#
   
   Don't forget to order 2 rubber grommets with the switch, one for installation plus one spare part.
   
   Don't reuse the rubber grommet because the radiator cuts into it forming a good seal during the installation.
   
   Install the grommet first, add some water to the switch and grommet and push it in position by hand.
   
   Everything fits perfectly.
   
   The part can be found for example at www.mgpartsuk.co.uk and other shops.
   
   Here a direct link:  https://www.mgpartsuk.co.uk/store/index.php?route=product/product&path=330_304_243&product_id=5359
   
   
   Happy motoring, Uwe
   
   
   Original part and grommet on the right, replacement and grommet on the left.
   
   Even if the dimensions look different because of the photo angle they are absolutely the same