Defender Variable Heater Fan Control Mod

The fan speed control on my 84 Series 3 was very stiff so I gave it a dose of WD40 and now it keeps springing back up to position 1 and the only way I can get the fan to run slow or fast it to hold the lever with my left hand in between gear changes. It feels like it has a strong return spring attached to it but I can't see one. Can anyone tell me what's going on please?

For those of you wanting to do this mod without spending silly money this is just a generic voltage regulator you can get from eBay for £5.39.

https://www.ebay.co.uk/itm/Universa...19R4os8w8177SPa0rhBw:rk:1:pf:1&frcectupt=true