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Rabbit hole

Nov 16, 2012
897
Catalina 310, 2000, #31 Santa Cruz
So more of the Rabbit hole here.. today i investigated why i'm not getting an alarm prior to engine start. Turns out that the PO broke a tab on the oil pressure switch and hard wired the two connectors together. i corrected this and will get a replacement switch tomorrow to make it right. however, even with the connector disconnected, i'm still not getting an alarm.. and my Tach is acting a little funny and showing either the correct RPM or about 500 RPM above actual. today i replaced the connector block behind the engine panel to make sure there were good connections.. but alas, the problem persists.. i'll have to check the back of the alternator tomorrow for connectivity for the Tach.. i'm thinking there must be a bad ground somewhere since i have no buzzer and the tach is acting funny. i'll jumper the alarm to see if that's the culprit tomorrow too..

eventually i'll recover all the issues the PO seems to have either worked around, or ignored.
Billy, I don't remember if you've got the M25XPB or a different engine, but here's a few wiring diagrams for the engine and controls. I made some changes to the schematic so it matches my wiring-I don't think a PO modified things, but it's likely there were changes during the production run.
 

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BillyK

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Jan 24, 2010
470
Catalina 310 Ocean City, NJ
Billy, I don't remember if you've got the M25XPB or a different engine, but here's a few wiring diagrams for the engine and controls. I made some changes to the schematic so it matches my wiring-I don't think a PO modified things, but it's likely there were changes during the production run.
PO definitely bypassed the oil pressure switch due to what appears to be a broken pin. So to get the lift pump going, he just jumped the circuit. i picked up a new pressure switch today at autozone. but of course you need a special socket to install it.. the switch was $10.. the special tool to install it is $15.. :facepalm:

Thanks for the updated diagrams.. i believe i have a bad buzzer.. i used a jumper wire to ground out the Water temp alarm wire (C) on the buzzer and i get a red light and a buzz.. when i ground out the oil switch side (P) there's no buzz but the light does go on very dim. When i measure the voltage across the buzzer for the oil switch side, it's registering only 4 volts when it should be in its alarm state of 12V. So i believe the buzzer has an internal fault for the low oil pressure alarm circuit and it isn't passing current..

i wonder if it's due to the broken pin on the oil pressure switch.. if the PO ran for hours with the buzzer in an alarm state on the oil side, i imagine it just burned it out.. These things are not designed to be in an alarm state for more than a minute or two. Seems like a logical progression of how this most likely played out. at least in my mind.
 
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BillyK

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Jan 24, 2010
470
Catalina 310 Ocean City, NJ
Check the connection to the fuel pump.
the lift pump is running with the oil pressure switch bypassed.. so i believe that part of the circuit is in good shape. unless i am missing what i should be looking for there..
 

Tom J

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Sep 30, 2008
1,601
Catalina 310 Quincy, MA
and my Tach is acting a little funny and showing either the correct RPM or about 500 RPM above actual
I had this issue with my tach a few years ago. I was able to clear the problem by turning the calibration screw on the back of the tach to the right and left a few times. Be sure to mark the original location of the screw, and don't turn the screw too far either way. The problem re-appeared for a few seasons, and I finally bought a new tach, and calibrated it with a hand held rpm counter.
 
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BillyK

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Jan 24, 2010
470
Catalina 310 Ocean City, NJ
I had this issue with my tach a few years ago. I was able to clear the problem by turning the calibration screw on the back of the tach to the right and left a few times. Be sure to mark the original location of the screw, and don't turn the screw too far either way. The problem re-appeared for a few seasons, and I finally bought a new tach, and calibrated it with a hand held rpm counter.
Thats funny.. i was talking to my father about doing exactly this on saturday... i'll give it a shot to see if that takes care of it! thanks Tom..
 
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Tom J

.
Sep 30, 2008
1,601
Catalina 310 Quincy, MA
Thanks for the updated diagrams.. i believe i have a bad buzzer.. i used a jumper wire to ground out the Water temp alarm wire (C) on the buzzer and i get a red light and a buzz.. when i ground out the oil switch side (P) there's no buzz but the light does go on very dim. When i measure the voltage across the buzzer for the oil switch side, it's registering only 4 volts when it should be in its alarm state of 12V. So i believe the buzzer has an internal fault for the low oil pressure alarm circuit and it isn't passing current..
Weird thing about those alarm buzzers is that the original alarms are 24v, but the replacement is 12v. My alarm had gotten intermittent , and then quit, so I ordered a replacement from Catalina Direct. The new alarm was noticeably louder, so I double checked the backs of the alarms, and noticed the different ratings. The old 24v alarm would definitely need a full 12v just to make any noise at all!
 

paulj

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Mar 16, 2007
1,356
Catalina 310 Anacortes,Wa
"(The new alarm was noticeably louder)"
The alarm for the oil is louder then the alarm for the temp warning.

paulj:hook2:
 
Dec 25, 2008
1,566
catalina 310 Elk River
The 24V version would explain why it seems to beep some times, as the alarm sounds the voltage would drop maybe just enough to stop sounding, when it stops the voltage would rises again and cross the threshold to sound again. Not sure if this was an intentional feature to distinquish between the 2 different faults, or just bad engineering. Never had a high temp situation so don't know the call.
 

BillyK

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Jan 24, 2010
470
Catalina 310 Ocean City, NJ
The 24V version would explain why it seems to beep some times, as the alarm sounds the voltage would drop maybe just enough to stop sounding, when it stops the voltage would rises again and cross the threshold to sound again. Not sure if this was an intentional feature to distinquish between the 2 different faults, or just bad engineering. Never had a high temp situation so don't know the call.

The manual states that the oil pressure alarm will be an intermittent tone and the water temp is a constant tone. But i have no idea if it works like this in practice as my low oil pressure alarm is not functioning. i do know when i jumped the water temp alarm it was a constant tone.

i should mention that my buzzer is a 24v one.
 

BillyK

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Jan 24, 2010
470
Catalina 310 Ocean City, NJ
Replaced the oil pressure switch today and reconnected the wires correctly to it.. now the low oil pressure light illuminates while the engine is off and goes off while the engine is on.. so at this point, i'm pretty positive replacing the buzzer will finish the job.
 
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