Re: Interesting recall

Posted by HH56 On 2019/3/3 13:43:57

I halfway suspected it was mechanical as very few use hydraulic switches anymore but still if vapors can affect the contacts that easily I wouldn't rule out the same in the hydraulic type switches.

No idea on the size of silicone vapor molecules suspected of causing the problem but if small enough they could pass thru a barrier membrane that is still capable of not admitting any liquid.

A good example of small molecule issues was found when Freon was banned. Because the R134 molecule is smaller than the R12 it was found that some of the old rubber hose formulations could not completely contain the new refrigerant hence a new hose formulation and different liner designated "barrier hose" became the standard. The old hoses will still mostly work in original R12 systems that are converted to R134 because the oil molecules that circulate with the refrigerant have penetrated into the original hose pores and act as a barrier to the smaller R134 molecules. If a hose had to be replaced and then the new refrigerant was used to fill the system the issue became obvious because the refrigerant started leaking and system was low in a fairly short period of time. A lot of mechanics spent a lot of man hours looking for leaks in fittings or changing components when the cars came back before it became common knowledge the hose was where the problem really was found and new barrier hoses became readily available.