Diagnosing the Low Oil Pressure Alarm

[Sailing Steve]

I've searched the board and the web to no avail...  The audible low oil pressure alarm does not sound when the key is turned on, and I wish to diagnose the problem.  I see the sending unit on the M35 is a single lead type, and I suspect it simply goes to ground to indicate its state.  I need to know however, if my theory is correct, and if so, does the sending unit provide a ground on sensing a low, or the proper operating oil pressure.  I haven't had a chance to put my meter on it yet to see if ground is even involved, but it is high on my to do list.

I'll work my way to the the engine panel and the buzzer, once I prove out the sending unit.

Any information on this problem is appreciated.

Thanks,
Steve

'90 C34 L'Abri

[Ken Juul]

According to the wiring diagram found in the Engine manual (Engine manual is found on the Home Page (c34.org) look under manuals) the sender goes to ground through the block.  My guess would be ground with no pressure, as pressure builds the switch is opened.  You could ask the question in the instrument forum at:  http://forums.torresen.com/sailing/index.php?sid=80cc82aea4082702cf54437a79b7db81 or just start troubleshooting.

[Craig Illman]

The 90 & 91 Seaward panels have an anemic buzzer located on a circuit board behind the panel for both low oil pressure and high water temperature. I could hardly hear mine. I replaced the panel and used my guages from my old panel. You should talk to Dennis at Seaward.  http://www.seawardproducts.com/   

- Craig

[Ron Hill]

Steve : If you have only one contact then the switch case should ground to the block.  However, I recall talks to Bill Nuttall about the M35A engine oil pressure alarm and in the back of my mind I remember something that it may not be that simple!!  It just maybe that the M35A engine uses a double contact sending switch?!?
Give him a call at (410)527-1225.   

[Sailing Steve]

Thanks gents.  I'm going to take a run at it this weekend, and I'll post my findings once I get it figured out.

Steve