I had a difficult cold start the other day, like the glow plugs were dead. But having had them all 6 changed with genuine parts 3 years ago, I thought that would be strange.

A VCDS scan this morning confirmed a coolant temperature sensor fault.

There are plenty on ebay around the £4 mark, GSF sell them for around £17, and genuine I believe is closer to £40.

I will be selling the car this year, so I am not bothered if the cheap one only lasts a year - does anyone have any experience with cheap versions of these? IS the very cheap version of these likely t be sending a wrong signal to the ECU or is it just a matter of durability - possibly?

I will be selling the car this year, so I am not bothered if the cheap one only lasts a year

Sorry, but I don't agree with your attitude on that point. If I were selling my vehicle I'd want to know it was right before someone drove it away. I wouldn't want to sell it suspecting that cheap parts were likely to fail in the next few months. Besides, for the sake of only £13 price difference, buy the reputable one and have some peace of mind.

My temp sensor failed and was replaced with GSF version about 4 years back. Still going strong.

That's what I was asking - is the £16 part of OEM quality. Good to know your GSF part has been OK for 4 years, that gives me the answer, thanks.

As far as my attitude, each to their own - I have previously sold my cars having rectified all the faults - the new owner did not even say thank you well done, instead they tried to negotiate the price down by 20%... there are not many Average Joes who truly appreciate a top condition used car.

As long as it's all working and I declare things that aren't working correctly my conscience is clear - something I have learnt is that for every £100 you put into a used car pre-sale you get back around £10-20 back in increased resale value, in other words putting on new tyres, new timing belt, wheel bearings, new service might increase "saleability" but adds no real value to the car. In that context a potentially non-top-quality temperature sensor is the least of my worries - especially when you consider that all the original black ones (from German OEMs) fail prematurely anyway, so OEM is not a synonym for quality and it wouldn't be the 1st or the last time, especially when dealing with VW (remember the plastic impeller water pumps for example...)...

I fancy a trip to GSF tomorrow and a Sunday DIY job...

You're right in what you say about extras not increasing the resale value of a car, I have the same situation. I had good lowered suspension fitted, decent set of 18'' alloys, hubcentric spacers, full led light conversion, front splitter etc etc etc ... whilst they make my car look a little better and drive a little better, not one of them will add any value to it. Just, when it comes to actual components I'd not skimp on them too much. It's my personal opinion only though.

As for the sensor, yeah it's been fine. Even seemed a fraction heavier than the original .... in my diseased brain, heavier = better quality. Not sure how true that is though.