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Author Topic: M35 low oil pressure alarm switch  (Read 734 times)

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John Langford

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M35 low oil pressure alarm switch
« on: September 05, 2018, 09:21:08 AM »

My oil pressure gauge is working but the oil pressure alarm function has stopped operating. I replaced the alarm on the panel itself but it still doesn’t sound when I turn the key or stop the engine. I suspect that the oil pressure alarm switch that is very hard to access low down on the port side of the engine.

Has anyone dealt with this problem. Any advice welcome.
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KWKloeber

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Re: M35 low oil pressure alarm switch
« Reply #1 on: September 05, 2018, 03:33:45 PM »

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.) :D

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





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Stu Jackson

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Re: M35 low oil pressure alarm switch
« Reply #2 on: September 06, 2018, 04:25:35 PM »

For continuity, this thread goes here:

http://c34.org/bbs/index.php/topic,10000.0.html

Notice it was the 10,000th topic posted!!! 
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womble

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Re: M35 low oil pressure alarm switch
« Reply #3 on: September 02, 2021, 04:24:58 AM »

I have a 1993 Catalina C30 with the 23HP M25XPAC engine with Seaward panel.

My Oil pressure sensing system has developed a fault - it never sounds.
I have tested the audible alarm functionality by shorting out the over temp alarm since both temp and oil sensors use the same audible alarm. Sounds fine.
I have disconnected the oil pressure switch and still no audible OR visual alarm indicators.
I recently replaced the ignition switch and IIRC the alarm worked fine. I have re-checked the ignition switch wiring and as far as I can tell all looks good - but I am suspicious that the fault developed after replacing the switch.
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womble

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Re: M35 low oil pressure alarm switch
« Reply #4 on: September 02, 2021, 05:23:29 AM »

RTFM!!!!!!
I looked at the wiring diagram and there is a breaker for the oil alarm in the panel right next to the red indicator.
I pressed it and now it works :clap
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KWKloeber

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Re: M35 low oil pressure alarm switch
« Reply #5 on: September 02, 2021, 08:14:54 AM »

[also (IIRC) the oil and temp were the same unit but different alarms. There’s two different tones, but the dual alarm is powered by one power source.  Is that NOT the case with your panel/schematic?]

Wombat

There’s something wrong with the wiring or schematic then. The fuse on the panel is supposed to protect EVERYTHING on the panel (and I believe also the engine space blower.)  Why? Because the panel, gauge power, gauge lights, alarm, have lighter gauge wiring.

So, no oil alarm, nothing else should work except the preheat and start if that breaker pops. 

There’s another breaker on the engine (stb side above the fuel filter) that breaks the feed TO THE panel.
« Last Edit: September 02, 2021, 08:19:33 AM by KWKloeber »
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain
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