Engine Alarm / Buzzer

[JerryRoss]

Peter,

Do you ever get a low oil red light that glows bright enough that you can easily see it in the daytime?

[pdenoncourt]

Jerry,

I haven't really noticed anything about the red light. It works well enough to see it in daylight, but the angle on the dashboard is not ideal, so I usually have to lean over to see if it is on.

Peter Denoncourt
Kite, C350 #72

[jking]

Here is another diagram which is easier to understand from another catalina site.

[TBOT422]

For all you electrical experts out there, What creates the supposedly 8 V shown in the diagram I found below on the Catalina 36 web site?

Buzzer Circuit 1.jpg (173.28 KiB) Viewed 5454 times

I measure about 9.5 to 10 V at that point on our boat. I thought the 8V was likely created by the 1K resistor circuit to ground, but when I disconnected that wire, I still measured 9.5V on the wire terminal lug. Is it coming from resistance in the buzzer, or from the ground path through the fuel lift pump. If it is from the path through the fuel lift pump, is that the reason the alarm is erratic, as the fuel pump could be in a variety of positions when you turn the engine off resulting in different resistances to ground and thus varying voltages seen by the alarm buzzer?

Our buzzer, like most of the others have noted, is very erratic. Sometimes it does not work at all, sometimes it is weak, and sometimes it is stronger. Never seems to be loud and 'alarming', but at least the Admiral can usually hear it.

Thanks

[Interlude35]

Our engine alarm buzzer & warning light are intermittent & when operate are not audible or visible. I hope to revise circuitry to provide dependable loud buzzer with a bright red light with loss of oil pressure. The feature that shuts off the fuel oil lift pump with the loss of oil pressure will be removed but hear our M35B can continue to run without the fuel oil lift pump.
The change is:
-Replace existing 2 post normally open lube oil pressure switch(LOPS) to a single post normally closed switch & wire it directly to the alarm buzzer P terminal. The LOP switch can be wired separately or I am using an abanded wire (#9 on Dwg #200360).
-Tie together the three previous connections to LOPS ( wires #10 & #18 & #17 on Dwg #200360)
-Wire #11 on Dwg #200360) will be left as is on the terminal block in consul- however- The connection from terminal block to the P terminal on alarm buzzer will be removed.
Expected Results:
Keyswitch in “I” position -(engine not running or LOP) strong alarm and warning light -FO lift pump operating
Keyswitch in “I” position (engine running) no light or alarm - FO lift pump operating
Keyswitch in “S” position - gloplugs & lift pump operate - no alarm or warning light
No change to start switch operation. Any Thoughts or comments are welcome. John & Marilyn Ferguson Interlude #316

[TBOT422]

The feature that shuts off the fuel oil lift pump with the loss of oil pressure will be removed but hear our M35B can continue to run without the fuel oil lift pump.

I'm not saying this is not true, but If it were true, it would completely invalidate the logic of the circuit as designed. It is my understanding that the circuit is designed to remove power from the fuel lift pump in the event of a loss of oil pressure in order to automatically shut down the engine in the hopes of preventing serious damage to the engine. Of course the engine will run for a short period due to fuel in the fuel filters, but if the fuel lift pump does not re-supply that fuel, the engine should shut down. In our installation the racor water separating filter is installed well above the engine and the fuel tank is below the aft berth. I see no way fuel flows uphill without the fuel lift pump unless the running engine provides some type of venturi suction effect to draw the fuel upward.

I can attest that the engine will start without the fuel lift pump as I have operated the engine numerous times with a failed pre-heat solenoid that is suppose to activate the fuel lift pump prior to engine starting and achieving proper oil pressure which then supplies power to the fuel lift pump. But that is only due to the fuel sitting in the secondary fuel filter. If that filter is empty (as in just been replaced), the engine will not start without power to the fuel lift pump.

It should be pretty easy to verify. Simply disconnect the power to the fuel lift pump, start the engine and see how long it runs before it dies.

Let us know what you learn.

[Interlude35]

Excellent points. It is not clear to me how long the engine will run without the fuel lift pump operating. I have been reading the posts in an attempt to learn more. I cannot test the engine’s ability to run without the fuel oil lift pump until the spring time. Grounding the “P” contact on the alarm module produced a loud buzzer and bright red light. They would be impossible to ignore which led me to using a normally closed low oil pressure switch that connects directly to ground. Still evaluating if possible to stop the fuel pump with reliable & strong buzzer/warning light on loss of oil pressure. The changes being consider are easily reversible and not too expensive.

John & Marilyn Ferguson
Interlude #316

[D&M]

I appreciate this is a very old thread but I wonder how many people are confusing their intermittent buzzer with the fact the low oil pressure switch alarm is actually a pulsating tone? There are three connections to an alarm buzzer: + which is of course 12v power, then a P terminal and a C terminal. The C terminal is connected to the water temp switch and is normally open. Thus there is no ground, when the water temp, hits about 100c (approx) a continuous (hence the C terminal) tone is heard.
In contrast the P terminal (P for pulsating) is connected to the oil pressure switch. If the tone is activated when your engine is running it means oil pressure has dropped and the switch has opened causing the power to the lift pump to be lost and with the key in the “i” position 12v will still be fed to the buzzer + meaning an alarm.
To test your alarm buzzer, simply open the engine panel on the pedestal. Check for a good battery voltage at the + terminal of the buzzer (turn the ignition switch to i with the key switch or connect a 12v battery). If good, disconnect both the C and P terminals and connect them to a good ground - one at a time. The C terminal should buzz loudly and continuously (and light up the warning light if it is still connected).
The P terminal should buzz with a pulsing tone and light up the warning light if connected.
At the moment only my C terminal emits a tone, so I have to buy a new buzzer to get the Pulse tone working.

(Edit to remove stuff about alternator output as it was confusing.)
Cheers,

[Bob]

I have just fixed this issue on my C34 MkII, with the M35BC engine, which I believe should be a similar set up to your boats. Firstly, this is an abomination of a system. I can only believe it was arranged this way so Westerbeke could claim it as a safety shutdown system for low oil pressure, as the normally open oil pressure switch cuts power to the fuel pump on falling pressure. This is a fallacy as it takes to long to shutdown under any conditions and in the case of our boats they will run nicely at lower rpms with no pump, just by siphoning fuel.

This is the post I made to the C34 forum after I stopped cursing the setup.

"With much help from Ken Kloeber I have the warning alarms fully functioning. It is a strange system, and I ended up replacing a good number of parts. The original issue was a weedy sounding alarm sometimes, progressing to no alarm at all.
1) the oil pressure switch had a loose terminal with an oil drip, so I replaced with a NAPA OP6624SB, 2-7psi normally open switch. The original switch checked out good.
2) the plastic key switch fell apart, I replaced it with a Cole Hersee, brass unit M-550- NO from Defender
3) once I was sure these parts would hold up I finally figured out there was actually 2 problems. The buzzer itself was bad, checked by testing across the battery. It was replaced with the original part Z4180 from Catalina direct. Also, the ground at the glowplug solenoid was poor. I removed the ground connectors and cleaned the bracket really well with emery cloth and put the grounds together on the same side of the bolt.

Once the above was done, there was battery voltage 14.2 volts at both sides of the buzzer when the engine is running with oil pressure. When the engine was stopped with zero pressure, there was battery voltage on the buzzer +ve terminal and 8.4 volts at the buzzer P terminal (pulsing alarm terminal) with the alarm screaming. Previously I had battery voltage at both sides of the buzzer when the engine was stopped, hence no alarm.

I had checked the resistor and it checked with 997 ohms. After everything was working I soldered a new resistor pigtail and a spare. I did this because I wanted to be sure nothing was corroded. I got the resistors (1000 ohms 1/2 watt) from Amazon $6 for 100 pieces!!! I didn't replace the 10A breaker as it checked good.

The system now wakes the dead.

As mentioned Ken's help was massive, I believe we figured out how this circuit works, with voltage flowing in different directions, depending on the oil pressure switch status, open or closed. The way the wiring is run and the connection points makes for a load of potential failure points.

All of the above not withstanding, I think Ron's solution of ripping it all out and wiring a normally closed oil pressure switch into the system makes for the most reliable system".

You need to get the correct wiring diagram for your boat, check all wires for continuity as vibration damages many of the wires that are not marine wire. Pay particular attention to the oil pressure switch connections. Shine up all the ground points around the glowplug solenoid and also check the terminal block in the panel in case there is corrosion in one of the connections. My boat is in fresh water so the issue of corrosion is greatly reduced.

[D&M]

Hi all,
Further to the above two posts, I finally received my new engine buzzer, this time from Westerbeke. Whilst waiting for it I did check the voltage at the fuel pump with the key switch in the I position and confirmed it was 12 v meaning the buzzer was short circuited and simply passing the 12v through the circuit (translation buzzer broke). I also had an open circuit on the ground wire containing the 1kohm resistor so replaced that and similarly to Bob I cleaned up the ground connections on the bracket holding the glowplug solonoid. After installing a new buzzer and doing the above the circuit (pulsing tone) works fine and very loud.

If you have a non working buzzer disconnect it from everything and connect the + terminal (not P) to a known good 12 volt source without any ground connection to anything. Then put a volt meter across the + and P terminal. You should measure 4.5v approx. This is the potential (difference) between the two connections and is why you measure 8 volts at the P terminal when it is installed in circuit. If you read 0 volts across the two terminals you have a short circuited buzzer. It would be the same as connecting both your red and black volt meter leads to the postivie terminal of your battery.
If you have 4.5v in the above test and still no working buzzer, the problem lays in the source 12V or the ground.
Have a good day!

[reinhardschumann]

I've had a lot of problems with my M35B oil alarm buzzer. There's a long discussion about this at C34.org. Here are some interesting facts:
--the design of this circuit is quite stupid
--design intent: shut down the motor when the oil pressure fails. Bad idea and design doesn't achieve the goal because the injector pump is quite capable of sucking fuel from the tank. It also creates a problem when the engine runs out of fuel: you can't prime the engine by turning the ignition key to ON and opening the bleed screw. You have to hold the key in the preheat position while you work the bleed screw. This doesn't work well when single-handing...
--design implemention: the buzzer input is driven high by the oil sensor to turn off the buzzer. That part works well if the sensor and wire are OK. The buzzer input is driven low by the resistance of the fuel pump coil putting much less than 12V across the buzzer, which is designed for 12V. So to increase the current and voltage, Westerbeke added a 1K resistor to ground to make the buzzer (barely) sound. The resistor is 1/2watt spec, which is too small in the engine compartment heat, so they are prone to fail.
--the buzzer: there are several manufacturers that make this buzzer: Intervox is one. They make two basic versions of this buzzer: a 12V version BRP4535S-12-CD and a 24V version BRP4535S-24-CD. I have the 24V version in my circuit and it does not work. (But it worked accidentally when my 12V went up to 16V dues to alternator problem.) The various manufactureres buzzer specs have a variety of different current and voltage requirements and they do not have current vs voltage graphs so it is impossible to determine whether their buzzers would work at the M35B design's operating point.
--buying a replacement buzzer: I bought a replacement buzzer from catalinadirect.com. They sent me the BRP4535S-24-CD. If you buy one from them don't accept it if that's the marking on the part. For other suppliers, look up the spec for the part and ask the supplier whether it will work. I have not yet tried the BRP4535S-12-CD buzzer, nor the "Jameco Valuepro 11D3120-LF-TA Audio Indicator and Alerts Buzzer Piezo 25 mA 12V" advertised on Amazon.
--modifying the circuit: there is a suggestion at C34.org to modify the circuit to drive the fuel pump from the ignition ON switch, and a corresponding change to the buzzer circuit.
--at present my buzzer does not buzz

[KenKrawford]

I replaced my buzzer about 8 yrs ago. At the time I could only find the 24 volt BRP4535S-24-CD version and it worked fine. The only drawback is that it is super loud. I purchased it from Allied Electronics - https://us.rs-online.com/product/icc-in ... m=70115827

[Interlude35]

I also had issues with my oil pressure buzzer and finally redesigned the circuit. If interested I have a project plan I can send to you. It has worked well for several seasons. The basic concept is replacing the oil pressure sensor with a dual acting sensor and some rewiring of the existing wiring harnesses. The oil pressure alarm now goes directly to ground when low oil pressure occurs and does not rely on the circuitous ground path used in the original design.