Water Temp & Oil Pressure buzzer not working

[Claude L.-Auger]

OK I did a search in the archives but either I did not do it right or I missed it and therefore have to ask for some help. Sunday when I shut the engine off (3GM30F), the buzzer didn't sound off as it normally does when there is no more pressure. I had run it at 3000 RPM for the last 20 minutes of the run. So today I go to the boat to investigate. Checked coolant level and everything is fine so there has been no overheating. Oil level is right where it should be and oil looks good. So I'm thinking it's an electrical issue.

Checked and cleaned connections on temp and pressure senders but they seemed OK even before I cleaned them. Checked connections behind panel and good there also. Wiggled and then undid & redid the 2 connectors behind panel and the 2 near tranny several time so see if I could get the buzzer to sound. I had left the key turned on and I could hear the hour gauge clicking so I know there is power at the ignition switch.

Checked the alarm itself with the switch on the panel and it does sound off when switch is triggered. Checked the wiring for damage and did not see any. Engine starts and runs fine so I do eliminate temp and pressure problems. At this point, I know the engine would have to overheat for the water temp alarm to sound off so I believe the problem is probably caused by the oil pressure sender. Can it be checked without taking it out and how ? Thanks for the suggestions !

 

[Bill Roosa]

The pressure switch is pretty easy to check. It is closed (low or no electrical resistance between the terminal and the engine) and opens when the pressure goes high enough. So to test the wiring just ground the wire to the switch on the engine with the ignition on and the alarm should sound. If the alarm sounds then replace the wire and the alarm should still sound. If not then the switch is bad or has lost its ground due to corrosion.

 

[Tim R.]

The problem is that you turned off the alarm. The alarm switch should be left on for it to sound when there is low oil pressure.

 

[kloudie1]

Claude, I am looking at the diagram right now.. The buzzer has separate connections for temperature switch, oil pressure switch, and the spare for the saildrive sealthat is not used on our 3GMF engines. The white/red wire on the buzzer is the saildrive connection.. so you might try moving the oil pressure wire (the yellow/white wire) to the saildrive connection to see if it works there?? Bill is right on.. if you take the yellow/white wire from the oil pressure switch and ground it to the block, the alarm should sound and the warning lamp should light.. If the buzzer works that way but not with the oil pressure switch, then the switch is bad. I am at my boat so I am sorry don't have a way to send this wiring diagram to you

 

[Lost Parent]

My buzzer on my Catalina sounds off when the key is turned on but after sitting for a few days itmakes a pathetic beeping sound which gets better as the days go on ?

 

[Claude L.-Auger]

Going back to the boat today to investigate further: Bill thanks for the tip I'll ground the wire to check. Tim, I'll check but from memory the switch on the panel has 2 functions: when pressed down it turns on the tachometer light and stays down. Throwing it up turns on the battery charger red light and sounds the buzzer. Again from memory I believe that side of the switch is spring loaded and returns to the OFF position when released. I'll check and report back. Kloudie thanks also. I printed the diagram last night but hadn't thought of using the sail-drive wire to check if the sender would work with it. Lost Parent I believe your comment indicates you seem to have a sporadic problem caused by corrosion or a buzzer that is starting to go bad. Thanks all.

 

[Claude L.-Auger]

Was at the boat today and did the checking suggested by Bill on that oil pressure sender wire. No sound. So bypassed the harness. Still no sound. Must be the buzzer but yet it sounds off when using the check switch (Tim it is indeed spring loaded). Tried connecting the bypass wire to the red/white wire going into the buzzer and it worked perfectly. Of course today I had the diagram and therefore it was easier. Cut off the yellow (solid yellow on my boat not yellow/white) wire at the connector to the buzzer coming from oil pressure sender and cut off red/white wire there also (for sail drive unit if so equipped). Connected yellow wire from oil pressure sender to section of red/white wire going into the connector. Turned key and buzzer sounded perfect. Started engine and buzzer quit as oil pressure was building. Shut engine off, great buzzer sound again. So I'm thinking I have a bad connector. Checked continuity on all 4 wires going into the connector. Everything perfect. Cut the connector off and check its continuity on a 4 wires and legs. Again everything perfect. Then I remembered reading somewhere that Yamar buzzers have diodes in them. At this point, I am convinced that the problem is with the buzzer but I have no other way of checking it. I happen to have to go near the Yanmar dealer tomorrow so I will take the buzzer and show it to them to get their opinion. Honestly, I am tempted to redo the connection like I had it for the test, in a permanent way, i.e. the yellow wire from the oil pressure sender connected to the red/white wire. I don't see any reason against but perhaps someone here knows better and will help me avoid a mistake. Thanks

 

[Claude L.-Auger]

Problem solved. As mentioned in last post, this morning I took the buzzer to the Yanmar dealer. According to what the tech told me, there are indeed diodes in the buzzer. According to him, one for each of the 3 items connected to the buzzer ! He could not tell me why other than venture a guess that perhaps the buzzer itself might be less than 12v. He also told me that the buzzer casing cannot be opened so replacing a diode is out of question. After they told me a new buzzer sells for $102 (Canadian) + tax, I asked if there was any problems cutting the yellow wire coming from the OP switch and connect it to the red/white wire going into the buzzer since the saildrive wire is not used. Tech said he could not see why not ? So being frugal I decided not to spend that kind of money and put the unused saildrive diode to work at last. The boat being a 84, I figured that diode had been getting a free ride for almost 30 years !!! So I did rewire the system, connecting the yellow from the OP to the red/white from the saildrive. White/blue Water Temp wire was left as is. Lights and buzzer now work like a charm, coming on when I turn the key, shutting off when the engine runs, and coming on again when killing the engine before turning the key off again. Case closed although I do not understand why that diode died other than plain wear and tear after 30 years. It is the one that gets to work the most since it comes on everytime that key is turned before starting the engine and after shutting it down. Hope the new connection works as long .

 

[kloudie1]

Good News, Claude ! .. I think the diodes are set in there as "check valves" so that when one switch triggers, only that one warning light on the panel works.. I think if all the alarms were connected directly to the buzzer, the buzzer would work but all the lamps would light. Anyway, good news!
I think I remember someone posting a simple schematic showing the diodes and their part numbers and the circuit so that a common Radio Shack buzzer could be used ..
http://www.radioshack.com/product/index.jsp?productId=2062398#tabsetBasic

 

[Ken13559]

Claude L, you're right that there are 3 diodes in there. I had this problem some years back and swap the Sail Drive buzzer with the Luboil one. You probably read my post back then.

 

[kloudie1]

Yes, Ken.. your post from a couple of years back.. I was looking for a part number on the diodes but I guess almost anything that can handle about 1 ampere and not break down at 14V reverse would work..

 

[rardiH36]

Very useful thread from everyone that contributed. Claude, thanks for coming back with description on what you learned during the trouble-shoot and fix process.

My 2QM20 buzzer has similar multi-circuit inputs. Several years ago I used the unused sail-drive input to provide an alarm to a "you-forgot-to-open-the-seacock" alarm that I DIY'd. Now I know about the diodes if one of the alarm circuits fails. In which case, I wonder if installing a pig-tail onto one of the remaining working inputs, then splitting it into two with in-line diodes will restore to the original number of inputs? For that matter, maybe adding seperate diode circuits might allow as the buzzer to serve as the alarm for as many inputs as needed?

 

[Claude L.-Auger]

As mentioned in original post I could not find anything in the archives. I wish I had Ken as it would have saved me a lot of searching in 80 + temp with near 75% humidity :cry:.

I don't know how you could add diodes & circuits to the Yanmar buzzer since it cannot be opened. Therefore you could not add anymore circuits to the current 4-prong pig-tail. Adding a pig-tail to the open prong could probably be done and installing diodes to that new added pig-tail might work but does seem like a lot of trouble. Wouldn't one be better to simply install a 2nd buzzer ?

FYI, Yesterday I didn't want to argue with the young tech at the Yanmar dealer about voltage differences for the buzzer itself and the role of the diodes, so I did a search last night knowing I had the info in my reference manuals for the HF radio. Diodes can be used as voltage regulators but the most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction) and not in the reverse direction. Common sense would want the buzzer to be 12vdc and the 3 diodes used as mentioned to isolate the sensors from one another. That being the case, the idea of using the unused saildrive diode to replace the faulty OP switch diode is perfect. I used the same yellow wire coming from the OP switch, but cut it near the buzzer and connected it to the red/white wire going into the buzzer after having cut that one too.

I deducted that production costs and economy of scale probably makes Yanmar (Hitachi) use the same wire harness and same buzzer for many types of engines and propulsion. So I figured first: since I don't have a sail drive the red/white wire is buried in the harness somewhere and second since it is connected to the buzzer, the diode is there too. It was just a matter of testing...and the test prooved that theory right.

The problem was that the diodes are not showing on the diagram since they're internal. All is well that ends well however. Thanks again to everyone who contributed.