General Electrical troubleshooting ?s

[QC]

Re: General Electrical troubleshooting ?s

Thanks both. I'll go through the list. Won't be hard at all Jack L with one issue. My boat does not have a traditional fuse "panel". It has independent fuses at various "drop downs" from the wiring harness (all at the helm). Most of the "custom" boats built here are set up this way. I assume that I can use the main hot lead coming to the helm for #3. Also, #4 would be the common ground (black) that runs through all of the gauges? #5 at idle?

 

[QC]

Re: General Electrical troubleshooting ?s

1. Voltage at battery with no load.<br /><br /> 12.58 Volts before I touched anything this AM <br /><br />2. Voltage at battery with load (lights & acc on).<br /><br /> 12.11 after 30 seconds. Running lights, interior lights and blower on<br /><br />3. Voltage at fuse panel with load.<br /><br /> 10.30 Volts at hot lead to key switch, same load as #2<br /><br />4. Voltage between fuse panel ground and battery neg. terminal with load (just use any wire to extend the multimeter)<br /><br /> .90 dropping to .85 volts over 10 seconds, same load as #2<br /><br />5. Voltage at battery with load and engine running.<br /><br /> 13.6 volts w/load at idle 14.3 w/load @1000 RPM, same load as #2<br /><br />A. A bad ground will cause excessive voltage to appear in reading 4.<br />B. A bad battery will show a big difference between readings 1 and 2.<br />C. A bad power lead will show with a big difference between readings 2 and 3.<br /><br />This seems to me like a combo of A and C.<br /><br />I know this sounds like a lot, but you should be able to do this in 15-20 min.<br /><br /> Would not have been a lot if I didn't decide to change the fuel filter before running her. Man, that sucks on my boat <br /><br />Is this showing that I have some flaky ground issues, but primarily a lousy power lead somewhere between the engine's main plug and the key switch?<br /><br />Also, if it is a bad power lead, why do the gauges act up even with the key off?

 

[jlinder]

Re: General Electrical troubleshooting ?s

1. Sounds OK<br />2. Sounds OK<br />3. A 1.81v voltage drop sounds a little high. Can you tell me what the guagge of the wire is, and how long it is from the battery to the front?<br />4. Looks like you have the same voltage drop on the ground as you do on the hot (.9 on the ground, and 1.8-.9=.9 on the hot). Unless both wires are bad equally the problem is probably either a high load, undersized wires, or both.<br />5. Sounds good.<br /><br />I would question the wiring. What guage is the wire for the main leads? Can you estimate the length of the wire?

 

[QC]

Re: General Electrical troubleshooting ?s

It is probably 10 gauge (maybe 8, I just can't read it, very faint, definitely larger than 12, which is there for comparison) and it runs about 14 ft.<br /><br />I just checked numbers again sort of while I was out there. I am getting the same no load reading now at the batteries and the helm, 12.7 volts (remember I ran it). Same three accesories on, 11.2 volts at the helm, engine not running, key off.<br /><br />Thanks for the help Jack L.

 

[QC]

Re: General Electrical troubleshooting ?s

I still think the running lights alone draw too much. I am going to double check that by itself as I don't even have the stern light in, only the bow lights . . .

 

[jlinder]

Re: General Electrical troubleshooting ?s

Something seems odd. With 10ga wire and a 14 ft run you would need about a 60 amp draw to get the voltage drop you are measuring. With 60 amps the wire would be getting pretty hot. I would doubt your draw would be more than 10 - 15 amps, and probably closer to 5-10 for this test. <br /><br />How old are the wires? It is possible to quickly take a nice heavy wire and run it from the battery pos term to the distribution point in the front? Even some 12 or 10 guage house wiring laying there for would work fine for these test purposes.<br /><br />If you have 10 guage in parallel with the existing wire the voltage drop should go from .9 to .45 volts if the original wire is good. If it drops more than that the original wire sounds a little flaky. Maybe the green meanies near the end just under the insulation?<br /><br /> You can even disconnect the original wire for the test, and see if the temp wire has the same voltage drop.<br /><br />In the long run you probably want to think about running heavier wire - 8 ga. or even 6 ga. In the long run it is not a big cost and adds some headroom

 

[QC]

Re: General Electrical troubleshooting ?s

I agree, something is odd. I have felt around for something hot and nada. It is a 2001 boat, very clean connectors, no signs of any detereoration anywhere . . . Running a supplementary lead would be easy. If I replace the original one I need to dissassemble the big main connector (is that called a CAN bus?) at the engine, right?

 

[jlinder]

Re: General Electrical troubleshooting ?s

Not sure how your wiring goes, but I can see it would be hard to replace the original wiring.<br /><br />You mention a connector, I assume it is not getting warm, correct? Maybe cleaning it would make a difference? Does the ground also go through the connector?<br /><br />Try the temporary supplementary wire and see what you get.

 

[QC]

Re: General Electrical troubleshooting ?s

The connector I am mentioning is the main one that all later Mercruisers use. It must be at least a 9 pin or so and provides temp, oil pressure, tach, trim, trim gauge, power and I assume ground. I am sure there is some other stuff in there, but you get the picture . . . Don't really want to cut into that bad boy Also, this harness style is used on a lot of boats around here and there are many additional drop downs for extra accessories. I have a hard time believing it is not sized for this load and especially the running lights which seem to freak it out the most . . . <br /><br />You've defintiely helped with my education. I'll run the supplemntal wire for some test numbers, but I am heading to the bow to see if I have something screwy going on at those two lights . . . Thanks again.

 

[jlinder]

Re: General Electrical troubleshooting ?s

Question: How big are the pins? I don't know the connector, but if it carries power the power pins should be pretty fat, expecially compared to the other pins.<br /><br />You might want to disconnect and try cleaning with a cloth. Look at the pins, if you see corrosion or dullness it could be an indication.<br /><br />It's just that I have seen so many problems at the connectors.<br /><br />BTW - to clean metal connections, like the pins, you can use a pencil eraser as long as the pins are sturdy enough to keep from bending.