The sensor is behind the grill, not sure how many, they've changed over the years with models, some have one centered, others may have two. Probably a problem with corrosion, generally they fail off, but they can go the other way.
Unfortunately, I can't help you with parts, I'm in the US and they stopped making them here in 83.
Unfortunately, I can't help you with parts, I'm in the US and they stopped making them here in 83.