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Oil Pressure Switch - Thread Size

Posted: Mon Feb 18, 2019 5:05 pm
by Alchad

Had a slight scare this morning when the oil pressure warning light came on (1390) , hopefully it was just the wire connecting to the switch which hadvirtually frayed through.

However thinking it might be the pressure switch, | started looking around for a replacement, and as Google often does, got diverted to an old thread on this forum


What I picked up from this is that the expert view was that the engine block was tapped 1/8" BSP PARALLEL (and 28tpi). This tied in with the inspection of my pressure switch as by (aged) eye, the threads looked parallel and the switch screwed right down into the block.

However, from the above thread, and others I found by searching, it appears lots of people have difficulty with replacement switches which seem to only screw in a few turns, which suggest the replacement switches might be 1/8"BSP TAPERED (also 28tpi), or even 1/8" NPT which is 27tpi. Having looked online, although difficult to tell from some photos, I'd say that the threads on new switches DO appear to be tapered.

Just wondered if anyone agrees with this logic, and if I'm right my only option for a new pressure switch is to use a tapered one, or possibly find an adapter from 1/8"BSPP to whatever thread size the new switches are.



Re: Oil Pressure Switch - Thread Size

Posted: Mon Feb 18, 2019 5:45 pm
by db2d
BSPP switches are available from
When ordering state the type required.