I feel bound to add weight to the letter from RH of Cumbria about the catastrophic failure of certain tyre pressure monitoring systems. In February 2010 three Siemens TPMS valves failed within 24 hours on my Citroen C5 and the fourth was on the way out (the circumstances are fully described in the attached letters to Citroen). I was very unhappy about Citroen UK’s response and pursued the matter with Continental in Germany, who had taken over the relevant Siemens business. Nobody in the chain admitted liability (they wouldn’t, would they?) and I considered reporting the case to VOSA, but knew that I would be wasting my time.

The valves were replaced under warranty and my expenses were paid in full (full marks to Holland on Sea Motors) but I discovered that there had been an advisory in June 2009 to Citroen dealers that valves should be replaced only in the event of deflation problems - not as a product recall. The original valves had aluminium stems with dissimilar metal cores, with the corrosion result you identified. The replacement valves apparently have aluminium cores and this raises an essential point about fitting new tyres for any of your readers with this type of valve. It is important to insist that the aluminium cores are retained, otherwise tyre fitters will throw them away and replace them with standard Schrader type cores with the of result corrosion again. The programming of these TPMS is very tricky and it is advisable to re-fit each wheel to the hub from which it came. This reduces the chances of having to have an expensive system re-programme at the dealership.

I haven’t checked lately on the status of the proposed EC mandatory fitment of TPMS in 2012, but there are better ways of doing it, e.g. inferring reduced rolling radius via ABS sensors as an analogue of tyre pressure. I believe that a set of TPMS will cost more than £300 plus re-programming when the batteries run out.