John
(I don't know which of your three threads you are following, so I copied what I said on the other one at the bottom below.)Ok, so you have anM35? it
IS NOT a 35B correct? (just to be sure.)

On the M35, the alarm sounds by completing a circuit from:
Your KEY switch (12 v positive),
TO the alarm (probably marked "B" or "+" on your new alarm)
Thru the alarm,
Out to the ground terminal (probably marked "S" on your alarm.)
That ground side of the alarm goes to the oil switch (via a blue 16-gauge harness wire.)
The oil switch on the M35, IF a PO hasn't changed something, is a SINGLE terminal switch. It is NORMALLY CLOSED; which means the alarm sounds with no or low oil pressure. It takes oil pressure to push the switch OPEN (i.e., break the circuit so the alarm has no electrical path to ground.)
Questions:
Do you have a Westerbeke or Universal panel -- can you post a picture? (As the OEM Seaward panel did not typically have an oil pressure gauge -- mine does but I added it.) The wiring connection for the Westerbeke panel/alarm is different than the Seaward panel/alarm.
Do you have the rubber "gummy bear" plugs on the wiring harness? (One at the engine end and one behind the panel)
Do you know how to use a multi-meter or have a 12v test light? I can show you how to troubleshoot this initially from the cockpit end. And determine if it's the wiring or the switch itself.
if you want to take this off list, just PM me or email me at KWKloeber@aol.com