alarm randomly going off. trying to track down source

turbocorrado

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so i recently made a thread about issues not revving out, i did the first splash this season tonight with it and im up from 3600 rpm to 4000rpm. so ive got some improvement there, but the alarm randomly goes off. there doesnt seem to be any rhyme or reason, coolant temp at 175, oil pressure 40+, gear oil full. i eliminated the out drive reservoir, which i believe leaves me with just the oil pressure and coolant temp alarms, at 1 point tonight the alarm was going off as soon as i started the engine. i started playing with wiring and starting it, which is how the gear oil reservoir was eliminated. next i went to the blue wire which was coming off the oil sender, all that did was kill my oil pressure gauge but alarm still sounding. there was a connector coming off the T for the oil switch with a purple/yellow wire and another wire ( cant remember what color, it was dark and i was in the middle of the river) i tried to disconnect it to see if alarm died but i couldnt get the connector off, so i started checking wires down the harness, found a connector on top of the intake manifold with a purple/yellow wire and another wire, it just had a orange cap on it connecting the 2 wires i assume, i removed the cap and started it with no cap, alarm was off, reconnected the cap and alarm stayed off.... drove it back to the marina with no issues. i dont have any pics as i didnt think of it till it was to late, but does anyone know if that connector with the orange cap is associated with the oil pressure system or if it was just a coincidence that the alarm went off
 

thumpar

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The sensor for the oil pressure gauge is different from the oil pressure switch that sets the alarm off. What exactly are you working on? Got a serial number?
 

turbocorrado

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The sensor for the oil pressure gauge is different from the oil pressure switch that sets the alarm off. What exactly are you working on? Got a serial number?

its a merc 4.3 v6 serial # is 0w657236 im pretty sure the oil pressure alarm switch has a connector with 2 wire on it, but the connector wouldnt come off. it was dark and getting late so i gave up trying to get that connector off
 

alldodge

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Purple/Yellow is for ignition ballast

Edit: 0w657236 shows as a V6 MPI, which drive alpha/bravo?
 
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alldodge

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its a 2bbl carb, and alpha 1

Looks like BAM got me again, checked Merc site and it shows carb as you say.

Got a pic of the plug you disconnected?

Purple/Yellow in this case is also used to bypass the oil pressure switch for the electric fuel pump during starting
 

turbocorrado

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Looks like BAM got me again, checked Merc site and it shows carb as you say.

Got a pic of the plug you disconnected?

Purple/Yellow in this case is also used to bypass the oil pressure switch for the electric fuel pump during starting

im hoping to go back to the boat tonight and snap some pics/ tamper with stuff
 

turbocorrado

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went back took some pics

this is what i disconnected and then the alarm stopped going off. there is a huge chance it was just a coincidence, what connector is this?


the connector with the 2 purple wires is the oil pressure switch for the alarm right??



this should be the coolant temp sensor for the alarm as well right?? yellow and black wires


and finally there is a small shaved down section on the sensor in the distributor, would that be causing any issues?
 
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Fun Times

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Pic # 1) Is for the TKS blocking diode which is used in the electrical system of MerCruiser V6 and V8 engines with TKS (Turn Key Start) carburetors. When the engine is warm but is not running, a temperature switch allows positive current to flow to the TKS heater module, while the diode prevents the positive current from reaching the electric fuel pump and the ignition system. This prevents the carburetor from returning to cold start mode when the engine is turned off but still warm.

So with that mentioned, in a hard to explain why, there is a very small chance that by you removing and connecting the diode, you may have inadvertently repaired/reset the intermittent phantom alarm due to by indirectly one of the wires eventually in a non direct way leads back to the ignition control module which happens to be one of the controllers for the audible warning alarm circuits only for the engine temperature sensor that is seen in your third photo with the yellow and black wires.
The other two alarm circuits for the engine oil and gear lube reservoir are separate from engine temperature circuit and is not ran through the ignition control module. Those two circuits are wired up through the Tan/Blue wire you should easily be seeing at the gear oil reservoir and the harder to find oil warning switch that should be mounted at the upper rear port side of the engine block sort of behind the intake manifold and almost next to the distributor cap/assembly.

The two sensors/senders in you second photo is used for the oil pressure switch to operate the fuel pump (two purplish wires) not the oil alarm while the blue wire is for the oil gauge. On the thermostat housing, (other side of the yellow and black wires) you should see a tan wire which is for the temp gauge.

For your last photo of the distributor, while the ignition sensor/area sort of appears dirty, you don't want the rotor wheel hitting the sensor...Needs to be a small gap like what is seen.

Should the warning horn ever sound off once again after it appeared to turn off from you removing the diode, next time it sounds try carefully removing both wiring connectors that plug into the ignition control module, let it sit for one minute unplugged and plug them back in and go for a ride to see if the horn comes back on. < If the horn stays off than that's the hard to explain part. But as favor, if you ever happen to have to do this procedure again and it seems to work for you in some way shape or form, please update this topic and let us know. Thanks and good luck.
 

turbocorrado

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Pic # 1) Is for the TKS blocking diode which is used in the electrical system of MerCruiser V6 and V8 engines with TKS (Turn Key Start) carburetors. When the engine is warm but is not running, a temperature switch allows positive current to flow to the TKS heater module, while the diode prevents the positive current from reaching the electric fuel pump and the ignition system. This prevents the carburetor from returning to cold start mode when the engine is turned off but still warm.

So with that mentioned, in a hard to explain why, there is a very small chance that by you removing and connecting the diode, you may have inadvertently repaired/reset the intermittent phantom alarm due to by indirectly one of the wires eventually in a non direct way leads back to the ignition control module which happens to be one of the controllers for the audible warning alarm circuits only for the engine temperature sensor that is seen in your third photo with the yellow and black wires.
The other two alarm circuits for the engine oil and gear lube reservoir are separate from engine temperature circuit and is not ran through the ignition control module. Those two circuits are wired up through the Tan/Blue wire you should easily be seeing at the gear oil reservoir and the harder to find oil warning switch that should be mounted at the upper rear port side of the engine block sort of behind the intake manifold and almost next to the distributor cap/assembly.

The two sensors/senders in you second photo is used for the oil pressure switch to operate the fuel pump (two purplish wires) not the oil alarm while the blue wire is for the oil gauge. On the thermostat housing, (other side of the yellow and black wires) you should see a tan wire which is for the temp gauge.

For your last photo of the distributor, while the ignition sensor/area sort of appears dirty, you don't want the rotor wheel hitting the sensor...Needs to be a small gap like what is seen.

Should the warning horn ever sound off once again after it appeared to turn off from you removing the diode, next time it sounds try carefully removing both wiring connectors that plug into the ignition control module, let it sit for one minute unplugged and plug them back in and go for a ride to see if the horn comes back on. < If the horn stays off than that's the hard to explain part. But as favor, if you ever happen to have to do this procedure again and it seems to work for you in some way shape or form, please update this topic and let us know. Thanks and good luck.

thank you so much.
i did find the oil warning switch by the distributor last night when i was peaking around, there is a similar one on the front as well. hopefully taking it out tomorrow, and there is a pretty good chance the alarm will go off, so i should be able to play with it
 

ralphy670

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Check the plug on the module mounted on top the manifold/riser as well. I have to clean mine yearly or I get an intermittent alarm. There have been a few that have had this problem in the past.
 

turbocorrado

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Check the plug on the module mounted on top the manifold/riser as well. I have to clean mine yearly or I get an intermittent alarm. There have been a few that have had this problem in the past.

the plug is clean, i checked it, but i will spray some contact cleaner on it anyway
 

turbocorrado

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took it out for a little this afternoon, about 2 seconds after going full throttle the alarm went off, put it in neutral and the alarm stopped when the boat leveled out. disconnected the oil pressure switch and went full throttle again. same thing happened, so i reconnected it and disconnected the coolant temp sensor and tried again, no alarm. went full throttle another 2 or 3 times still with no alarm, so it looks like its the coolant temp sensor that is the problem
 

Fun Times

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turbocorrado

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But did you reconnect the temp sender and try again? Hate to see you spend money on a sensor that may not need to be changed even though the cost is low for temp sensor which is part number 805218T, http://www.iboats.com/Boat-Parts-Acc...6798&q=805218T

http://www.iboats.com/4-3L-CARB-ALPH...iew_id.1682568

yeah, i plugged it back in and alarm sounded when gassing it, i ran it with the connector disconnected. gonna order the sensor and run it with the sensor unplugged till the part comes in... i dont really need an alarm, i check gauges constantly, im used to it after driving a modified vw
 

Fun Times

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yeah, i plugged it back in and alarm sounded when gassing it, i ran it with the connector disconnected. gonna order the sensor and run it with the sensor unplugged till the part comes in... i dont really need an alarm, i check gauges constantly, im used to it after driving a modified vw
It could be the sensor but since you plan to run it again, If you didn't have a chance last time out then do yourself one last favor, connect the sensor back up and unplug the 2 connectors to the ignition control module, check the connectors and reinstall them and see if the horn come back.

Happy boating. :usa::usa2:
 

NHGuy

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To test the sensor check for continuity. That switch is normally open (off) til 195 degrees for carb applications, and higher for EFI. If your ohms go infinite (approach zero) or your continuity tester beeps below 195 the switch is no good. Or if you use a powered test light same thing. If it lights cold it's not working right.
You didn't mix up the temp sensor with the temp alarm switch right? They look pretty similar on my boat.
 
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mjf55

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.... If your ohms go infinite (approach zero) or your continuity tester beeps below 195 the switch is no good. Or if you use a powered test light same thing. If it lights cold it's not working right.
......
NHGuy, just to clarify, you dont mean ohms to infinite ( basically open circuit ) do you? I think you mean closed circuit ( as you said in the parenthesis, go to zero ).
 
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