Hopefully an S3 E-type Forum member can shed some light on the Borg Warner model 12 installed Pressure/Safety switch - C37440. Can’t recall seeing a wire connected to it when the car was dismantled so hoping another S3 BW12 iowner can elaborate on the function of the switch.
Dick Maury gave me a pretty good interpretation of how he thinks it may have been designed to function thinking maybe later recalled via a Service Bulletin. Haven’t found any SB… yet. So any and all help would be most appreciated. The pressure switch isn’t covered in the ROM or at least I couldn’t find anything!
None other than that it could be Emissions related (but I don‘t know how exactly) and that scparts list it as up to 2E3922, 2R53929, 2P1870, 2P50069, 2K2196, 2K50081, 2G1014, 2G50036, 2F1003 and 2F50000…
Looks like a regular idiot light switch, but of course calibrated differently or normally open. I‘ll think about it!
In the V12 E-Type wiring diagram, it is a closed switch with no transmission oil pressure which completes the ground for the starter relay. When the engine is running, the transmission has oil pressure and the switch keeps the starter from working. I have never seen a V12 E-Type wired this way even though the wiring diagram shows it.
Neat, so it‘s not equipped with the kind of ignition Switch that prevents cranking twice from the run Position? And why on the transmission and not the Engine?
You would have to ask the engineers at Jaguar. If they had used engine oil pressure, they could have used the existing oil light switch and then it would not matter if manual or automatic transmission.
As the owner of two cars with BW-12 transmissions, this is of great interest to me. But I could have guessed all day without coming up with that idea on its function.
If I have this correct - if that pressure switch (NC) fails in the Open position the car could never be started using the starter! Now that’s really SAFETY!!! LOL Guess BW12 owners need to look at the Starter/Ballast relay to see if the W2 terminal is permanently grounded or reliance on the BG wire to the C37440 pressure switch. I, too, have never seen one connected ALTHOUGH both the S3 E-type and XJ sedan series show the wiring/switch in their respective schematics!!!
Hi Dick,
The pressure switch is part of the emissions control system where fitted. It is used to operate a solenoid valve which switches the inlet manifold vacuum sensing position for ignition advance at a certain road speed. Details below.
Hope this helps, but it doesn’t explain the wiring diagram,
Bob
Hi Bob,
You’ve a sharp eye. Never thought looking into the Owners manual for the answer! Thanks for educating me on that particular feature. Will look further into the system!
More sense but still lacking information. From the looks of the switch it’s probably sourced from “Smiths” but the particular Part Number or operating characteristics remains a mystery (except to Jaguar). I’m sure on the Jaguar Parts Drawing all this information would be revealed.
