Last year I bought a new oil pressure sender/switch (Beck/Arnley brand) to replace my erratic original oil pressure switch. Just last week I finally got motivated to swap it in.

The original one was screwed in about 7 turns. Hardly any threads were showing when seated.

The new one screws in only about 2-1/2 turns when it seats. Most of the threads are still showing.

I understand it is a tapered thread. But the Beck/Arnley seems a bit wider at the tip so it seats sooner.

The Beck/Arnley seems to work fine: no leak where it screws into the iron and consistent readings at the gauge.

But the fact that it is anchored in the engine with less than half as much brass stem does not instill great confidence.

Anybody else ever run into this? Not worth worrying about?

 

Is it the right thread pitch? If so, make it snug and you should be good.

 

The fitting was definitely in there snug--definitely in as far as it could go--bottomed out at 2-1/2 turns. I can't be absolutely positive that it had the same thread pitch (don't have a thread gauge--yet) but when placed side by side with the original, it sure looked identical by eyeball.

Since posting this problem here, I reported this problem to the vendor and they contacted a Beck/Arnley tech rep. The B/A tech rep came back with specifications for the thread diameters both at the tip and at the wider part of the thread (9.36mm, 9.90mm). I measured the Mazda original and it matched the specs. But the B/A unit measured too wide at both parts of the thread--0.14mm larger in diameter at the tip and 0.20mm larger at the base.

So I acquired another B/A oil pressure switch (same part number) and this one matched the specs. Installed it today. This one is seated in the iron with 7 turns of the threads--in there a lot more securely.

Not sure what happened there. Manufacturing variation? Wrong part in the box?

Anyway, problem solved.