Wondering if anyone can shed some light on this for me:
I have a 1993 Catalina 270. I went to start the engine the other day and after it cranked 2 or 3 times, the instrument panel totally died. Since then, the instrument panel won't light up and nothing happens when I turn the key. Batteries are fully charged and all of the other electrical systems on the boat are still working.
Engine is a Perkins M20, and as far as I can tell the ignition wiring follows the attached wiring diagram exactly.
My knowledge of electrical systems isn't too advanced (I've read Don Casey's book on the subject, as well as lots of internet stuff). I browsed through Stu Jackson's Electrical Systems 101 (http://c34.org/bbs/index.php?topic=5977.0), but unfortunately the link to "Engine Starting Issues - that pesky negative ground connection" just led me back to the C34 home page. Anyway, I broke out the multi meter and this is what I've found so far. If anyone is able to make sense of it or offer any advice, I would be most appreciative.
Findings:
-When testing the brown power wire to the ignition switch, this is what I find: It has 12+ volts when using any of the ground wires in the system when the switch is off (no key, or position P or O). With the switch in position 1, 2, or 3, it has about .5 - 1 volts when using any of the same ground wires. When using an independent ground (from the fuel gauge, which is wired separately and uses a different bolt on the engine as it's ground), I measure 12+ volts in all switch positions.
-The tab on the ignition switch where the brown power wire attaches (marked "30" on the diagram) has continuity with each of the other tabs on the ignition switch when the key is turned to the appropriate position.
- Using any of the ground wires in the system, and testing the voltage at the various tabs on the back of the ignition switch, the tabs each show about .5-1 volt when the key is switched to the appropriate positions. I tested this with everything hooked up as well as with each tab individually (i.e. when I tested the white wire, it was the only one plugged in, same for brown/red and white/red) and got the same results.
- When I repeated that test with everything unplugged from the back of the switch (except the power), I got 12+ volts between each tab and any of the ground wires in the system, with the key turned to the appropriate position.
-When I hooked everything back up and repeated the test again using an independent ground, I got 12+ volts at all tabs with the key in the appropriate position.
-When I put the volt meter's positive lead on any ground wire in the system and the negative lead on the independent ground (fuel gauge), I measured 12+ volts with the key in positions 1, 2 and 3.
-Some resistance measurements:
system ground to independent ground - 20 ohms
white wire at ignition switch (goes to other instruments) to system ground - 5 ohms
brown/red wire at ignition switch (goes to glow plugs) to system ground - 45 ohms
white/red wire at ignition switch (goes to starter solenoid) to system ground - 1.5 ohms
-I'm pretty sure the wiring is original (24 years old), and the boat has lived in the water year 'round in Florida for all of that time, so I know there is some degree of corrosion and resistance in the wires.
All of this leads me to believe that power is leaking to the ground wires when the ignition is turned, and therefor there is no electrical potential to light the instrument panel, flip the relay, or activate the starter solenoid. Again, I'm still trying to learn about electrical systems, so that belief may be way off.
Someone on another forum suggested that it might be an open ground due to a loose connection. I went down to the engine and gave a tug on all of the wires in the 10 pin connector and nothing seemed loose. I did the same at the connector behind the instrument panel and everything was solid there too. I'm not sure, but I think the fact that I can measure 12+ volts between the switch's power wire and the system ground wires (although only with the switch off) rules out the open ground??
Any other problems anyone can think of that might explain this? Is my "power leaking to ground wires" theory just a simpleton's misconception of what is happening here?
Also, because the engine cranked a few times and then everything died suddenly, it leads me to wonder if in addition to the above problem, I may have fried some other component of the system.
Thanks as always for any knowledge you can throw at this one.
Kevin
P.S. Another thing I found that really baffled me was that when I unplugged the connector down by the engine to check the contacts, I measured 12 volts between the brown power wire and the ground wire on both sides of the disconnected plug. In other words, on the half of the connector attached to the engine (and grounded to the bolt on the engine) I measured 12 volts between the power and ground contacts. The part I can't figure out is when I tested the same brown power wire with the ground contact on the other half of the connector (the one that runs back to the instrument panel), I measured 12 volts again. That confused me because the other end of that ground wire is just connected to the instruments in the panel.
I have a 1993 Catalina 270. I went to start the engine the other day and after it cranked 2 or 3 times, the instrument panel totally died. Since then, the instrument panel won't light up and nothing happens when I turn the key. Batteries are fully charged and all of the other electrical systems on the boat are still working.
Engine is a Perkins M20, and as far as I can tell the ignition wiring follows the attached wiring diagram exactly.
My knowledge of electrical systems isn't too advanced (I've read Don Casey's book on the subject, as well as lots of internet stuff). I browsed through Stu Jackson's Electrical Systems 101 (http://c34.org/bbs/index.php?topic=5977.0), but unfortunately the link to "Engine Starting Issues - that pesky negative ground connection" just led me back to the C34 home page. Anyway, I broke out the multi meter and this is what I've found so far. If anyone is able to make sense of it or offer any advice, I would be most appreciative.
Findings:
-When testing the brown power wire to the ignition switch, this is what I find: It has 12+ volts when using any of the ground wires in the system when the switch is off (no key, or position P or O). With the switch in position 1, 2, or 3, it has about .5 - 1 volts when using any of the same ground wires. When using an independent ground (from the fuel gauge, which is wired separately and uses a different bolt on the engine as it's ground), I measure 12+ volts in all switch positions.
-The tab on the ignition switch where the brown power wire attaches (marked "30" on the diagram) has continuity with each of the other tabs on the ignition switch when the key is turned to the appropriate position.
- Using any of the ground wires in the system, and testing the voltage at the various tabs on the back of the ignition switch, the tabs each show about .5-1 volt when the key is switched to the appropriate positions. I tested this with everything hooked up as well as with each tab individually (i.e. when I tested the white wire, it was the only one plugged in, same for brown/red and white/red) and got the same results.
- When I repeated that test with everything unplugged from the back of the switch (except the power), I got 12+ volts between each tab and any of the ground wires in the system, with the key turned to the appropriate position.
-When I hooked everything back up and repeated the test again using an independent ground, I got 12+ volts at all tabs with the key in the appropriate position.
-When I put the volt meter's positive lead on any ground wire in the system and the negative lead on the independent ground (fuel gauge), I measured 12+ volts with the key in positions 1, 2 and 3.
-Some resistance measurements:
system ground to independent ground - 20 ohms
white wire at ignition switch (goes to other instruments) to system ground - 5 ohms
brown/red wire at ignition switch (goes to glow plugs) to system ground - 45 ohms
white/red wire at ignition switch (goes to starter solenoid) to system ground - 1.5 ohms
-I'm pretty sure the wiring is original (24 years old), and the boat has lived in the water year 'round in Florida for all of that time, so I know there is some degree of corrosion and resistance in the wires.
All of this leads me to believe that power is leaking to the ground wires when the ignition is turned, and therefor there is no electrical potential to light the instrument panel, flip the relay, or activate the starter solenoid. Again, I'm still trying to learn about electrical systems, so that belief may be way off.
Someone on another forum suggested that it might be an open ground due to a loose connection. I went down to the engine and gave a tug on all of the wires in the 10 pin connector and nothing seemed loose. I did the same at the connector behind the instrument panel and everything was solid there too. I'm not sure, but I think the fact that I can measure 12+ volts between the switch's power wire and the system ground wires (although only with the switch off) rules out the open ground??
Any other problems anyone can think of that might explain this? Is my "power leaking to ground wires" theory just a simpleton's misconception of what is happening here?
Also, because the engine cranked a few times and then everything died suddenly, it leads me to wonder if in addition to the above problem, I may have fried some other component of the system.
Thanks as always for any knowledge you can throw at this one.
Kevin
P.S. Another thing I found that really baffled me was that when I unplugged the connector down by the engine to check the contacts, I measured 12 volts between the brown power wire and the ground wire on both sides of the disconnected plug. In other words, on the half of the connector attached to the engine (and grounded to the bolt on the engine) I measured 12 volts between the power and ground contacts. The part I can't figure out is when I tested the same brown power wire with the ground contact on the other half of the connector (the one that runs back to the instrument panel), I measured 12 volts again. That confused me because the other end of that ground wire is just connected to the instruments in the panel.
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