Hello,
Recently, on two occasions we lost power to the instrument panel on our 2002 C36 MkII and found the 20A breaker feeding the instrument panel to have tripped.
With the help of a previous forum post I was able to find a pink wire protruding out of the wire loom that goes around the aft port side of the engine that appears to have been shorting to the engine case for some time.
(too bad they put the split in the wire loom around the turn facing the engine instead of away)
My question is:
What is the purpose of this pink wire, and if it was shorting to ground, would it have been able to trip the 20A breaker. In referring to the Universal engine manual, and thinking we have the Admiral Panel, I believe the pink wire goes from the alarm buzzer to the Alternator along with the light blue wire from the oil pressure switch? What alternator connection is this?
Also, wondering if my intermittent alarm buzzing is related to this? Also, my tach is now very erratic at low rpms, but seems to hold steady at higher (>2000) rpms.
Sorry, one thing at a time!!
Can anyone shed some light on this pink wire causing the tripped breaker for me?
thanks,
Mike
Mike Ashmore
Pleiades
2002 C36 Mk II #2102
Alameda, CA
I feel sorry for anybody trying to read the wiring diagram for the Catalina 36. Not for the timid.....
Anyway, power from the battery is fed through the 20 amp circuit breaker. From there, power goes to the "B" terminal of your ignition switch. When the switch is rotated to the first position, this activates the "I" terminal, supplying power to most of the things in the instrument panel, then out to the high side of the oil pressure switch and to the EXC terminal of your alternator (if you have one). The pink wire then connects either to the high side of the oil pressure switch or to the EXC terminal and runs back to the instrument panel to power the high side of the alarms. When you have something wrong with the pink wire, then everything you're describing fits.
A dead short in the pink wire to ground essentially shorts out everything the "I" terminal supplies power to and would only trip the breaker when the key is either rotated to the first or second position. The pink wire going to the alarms is important, but the pink wire not shorting is critical.
Note that some boats have alternators that don't have an EXC terminal and the power coming from the instrument cluster is simply looped back to the pink wire, usually via a light blue wire inside the port side of the engine wiring bundle. My boat is like this and I've actually teed into this pink/blue junction as input to the ignition lug on my Balmar regulator.
Your crazy tachometer could be cause by issues with the pink wire, but get the pink wire stable first. Crazy tachometers can have several causes.
Nick Caballero
Retired C36/375IA Mk II Technical Editor
Thanks very much for your response Nick, I was hoping you would answer.
Ok, it does sound like the pink wire shorting to ground would have a direct connection to the +12V on the high side of the oil pressure switch via its connection to the light blue wire at or in our cases near the alternator. I also have an Heart Interface incharge external regulator that has the "reg on" terminal connected to the junction of the pink and light blue wires near the alternator.
Now, a crazy thing, to me, is that inside the instrument panel the pink wire comes into the 12 position terminal block and then goes nowhere!! It doesn't go to feed +12V to the buzzer!! From my photos(need to take apart
again), it looks like the +12V for the buzzer is coming from the +12V that is looped from the 10A breaker to the fuel, voltmeter, temp, tach and then to the buzzer?? Does this make any sense to you? BTW, I really appreciated your oil pressure/ignition drawing you did.
Mike Ashmore
Pleiades
2002 C36 Mk II #2102
Alameda, CA
The pink/blue junction feeding your Heart "reg on" terminal is similar to what I'm using it for on my Balmar regulator. No problem here.
According to the schematic, the pink wire returns to the instrument panel via pin #9 of the terminal strip and the other side of pin #9 is a purple/black wire that then goes to the high side of the alarms (buzzer, oil light, temp light). Even if the pink wire is essentially floating upon return to the panel, a short in the pink wire to ground will still trip the breaker because the other end of the pink wire is common to the "I" terminal wiring of the key switch
The original reason for the pink wire might have been for a bit of circuit integrity checking when starting. It might be that the PO had some issue with the pink wire, decided to move it to an unused pin and then power the alarms by tapping into the fused ignition circuit inside the instrument panel. Properly done, no problems here.
What puzzles me is that pin 12 on your terminal strip was available to move the pink wire to. Normally this is used for the temperature switch (not the temperature gauge), but I realize not all of our boats have this feature. I have not compared the wiring diagram with reality, so there could be some errors in pin number, etc. Not to mention that modifications to the factory wiring makes troubleshooting all that more interesting.....
Finally, thanks for the shout-out on the schematic. Please bear in mind this is not a complete schematic of the instrument panel or engine harness - just a chosen subset as it pertains to engine preheat, lift pump, oil switch, and buzzer interactions.
Nick Caballero
Retired C36/375IA Mk II Technical Editor