Hello to all! Okay...here goes! While motoring my sailboat (1977 25ft O'Day with 2002 Honda 8hp 4stroke outboard)I noticed that - if I turn on all instruments (running lights, cabin lights, mast light, radio, & knot meter) the knot meter doesn't work. I checked the battery (brand new Optima Blue D34M) using a volt meter...it registered 13.5v with engine OFF & instruments ON and registered BELOW low with engine ON & instruments ON (testing alternator). I then checked each instrument separately - the knot meter did not work ONLY when the running lights were switched on. So... I followed the wires from the knot meter & then pulled out the intrument panel - the knot meter has two gray wires (that I can see)...one wire goes to the propellor (hull) & the other wire goes to the instrument panel. The wire to the instrument panel is sliced open to reveal three smaller wires (red, green, brown)...the red is attached to the knot meter fuse, the green is attached to the running lights fuse, & the brown is not attached to anything. Everything appeared to work fine last year...??? The only new thing that I did this year was to replace the light in the mast light - it didn't work last year. Help - I am so confused...is it the battery, wiring, alternator, etc??? Thanks in advance! Karen
Electrical problem - knot meter? wiring? battery?
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H
Hugo
It's all about the current
Checking the voltage will only tell you if you have enough potential in the battery to drive the system. What you probably have is a current issue. Your lights are now pulling so much current that your know meter is competing to get enough power. My question is if two of your wires are connected to positive sources where is your ground? Electricity in a 12V DC system needs a positive (usually red) and negative set of wires to operate. Where is your negative? I would take your voltmeter(it probably a multmeter) and set it to measure current (AMPS). Then place it "in-line" (in between) the red wire and the know meter. Then measure the current with the lights off, and lights off. If the current drops your culprit is that it's tied to the same circuit your lights are on. In which case I would look into moving it into it's own circuit.
Checking the voltage will only tell you if you have enough potential in the battery to drive the system. What you probably have is a current issue. Your lights are now pulling so much current that your know meter is competing to get enough power. My question is if two of your wires are connected to positive sources where is your ground? Electricity in a 12V DC system needs a positive (usually red) and negative set of wires to operate. Where is your negative? I would take your voltmeter(it probably a multmeter) and set it to measure current (AMPS). Then place it "in-line" (in between) the red wire and the know meter. Then measure the current with the lights off, and lights off. If the current drops your culprit is that it's tied to the same circuit your lights are on. In which case I would look into moving it into it's own circuit.
P
Paul I aboard "One Slip"
sounds like a short to me
Hugo is correct in that there has to be a ground (negative)connection for the instrumentation (and every other electrical device for that matter). You need to find the ground leads. Usually the positive and negative leads are jacketed in the same wire (but maybe not in your case). You can verify that you have a positive and a negative lead for the knotmeter and the running lights by using your voltmeter. With the positive lead connected to the positive voltmeter input and the negatives connected likewise the meter should read +12 to 14 volts when the circuit is powered. The red line going to the knot meter fuse is likely the positive for the knotmeter. The green wire may or may not be the positive for the lights. You need to find out. If both the red and green wires are positive there should be no voltage between them at any time. Once you have identified the positives and negatives you can measure voltage across the knotmeter. Connect the positive lead of the voltmeter to the positive knotmeter lead and the negative voltmeter lead to the negative knotmeter lead. Keep the meter connected and see what happens when you switch on the running lights. My guess is the voltage will drop significantly. If so I would suspect a short between the positive side of the running lights (possibly the green wire you mentioned)and the ground side of the knotmeter. When you switch on the running lights the positive lead to the lights begins to carry power. If it is touching the negative lead from the knotmeter.... there is the short. It results in no power getting to the knotmeter. You didn't necessarily cause the problem by doing anything. On a 30 yr old boat, shorts can happen due to deterorated insulation or rusted wiring connections or wires chafing in drilled holes and channels. Then again, you may track it down to an area you were working in and inadvertaintly disturbed a wiring run. I have accidently broken connections in the main panel while working on other things in the panel. If you do find a short, try to detrmine where it is. It will be easy to fix if the short is at a connector or screw terminal. If it is in the middle of the a wiring run, the best thing to do is rewire both the knotmeter and the running lights. Sorry for the complicated answer. Good luck and let us know how it turns out.
Hugo is correct in that there has to be a ground (negative)connection for the instrumentation (and every other electrical device for that matter). You need to find the ground leads. Usually the positive and negative leads are jacketed in the same wire (but maybe not in your case). You can verify that you have a positive and a negative lead for the knotmeter and the running lights by using your voltmeter. With the positive lead connected to the positive voltmeter input and the negatives connected likewise the meter should read +12 to 14 volts when the circuit is powered. The red line going to the knot meter fuse is likely the positive for the knotmeter. The green wire may or may not be the positive for the lights. You need to find out. If both the red and green wires are positive there should be no voltage between them at any time. Once you have identified the positives and negatives you can measure voltage across the knotmeter. Connect the positive lead of the voltmeter to the positive knotmeter lead and the negative voltmeter lead to the negative knotmeter lead. Keep the meter connected and see what happens when you switch on the running lights. My guess is the voltage will drop significantly. If so I would suspect a short between the positive side of the running lights (possibly the green wire you mentioned)and the ground side of the knotmeter. When you switch on the running lights the positive lead to the lights begins to carry power. If it is touching the negative lead from the knotmeter.... there is the short. It results in no power getting to the knotmeter. You didn't necessarily cause the problem by doing anything. On a 30 yr old boat, shorts can happen due to deterorated insulation or rusted wiring connections or wires chafing in drilled holes and channels. Then again, you may track it down to an area you were working in and inadvertaintly disturbed a wiring run. I have accidently broken connections in the main panel while working on other things in the panel. If you do find a short, try to detrmine where it is. It will be easy to fix if the short is at a connector or screw terminal. If it is in the middle of the a wiring run, the best thing to do is rewire both the knotmeter and the running lights. Sorry for the complicated answer. Good luck and let us know how it turns out.
H
Higgs
The British way
I am sure this is not what you are looking for, but if it were me, and my knot meter I needed it, I would just let it go. You say with the cabin lights on, it does not work - if it works when they are off, I would live with that since the time would be minimal when the cabin lights and the knot meter would be on at the same time.
I am sure this is not what you are looking for, but if it were me, and my knot meter I needed it, I would just let it go. You say with the cabin lights on, it does not work - if it works when they are off, I would live with that since the time would be minimal when the cabin lights and the knot meter would be on at the same time.
K
karen
Thanks for your help!
Thanks for the help - I'll recheck the wiring & look for the ground. I sort of thought it might be a problem with the ground wire. I'll let you know what I find out. Have a great summer!
Thanks for the help - I'll recheck the wiring & look for the ground. I sort of thought it might be a problem with the ground wire. I'll let you know what I find out. Have a great summer!
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