Measuring voltage can be misleading unless the voltage is measured when the circuit being measured is under load. Digital voltmeters require very little power to read voltage and, even with lots of resistance in an unloaded circuit under test can indicate full expected voltage. Once the normal load on the circuit is applied, the voltage will drop to indicate the true voltage at the load.
One very good source of problems in many of the older boats is the one or more multi-pole connectors in the engine wiring harness. They have often been there for twenty or more years without being touched and corrosion build up due to lack of current flow across the individual connectors can lead to excessive resistance in the various circuits, false alarms and poor starting. I suggest as a first approach to trouble shooting any engine related starting or alarm problems, finding the connector(s), often there are more than one, pulling them apart and reconnecting them several times to clean corrosion off the contacts and then testing to see if the problem is resolved. If that resolves the problem, I am an advocate of removing the connectors completely and replacing them by cutting each conductor back to good, corrosion free wire and rejoining them using appropriately sized and crimped heat shrink butt connectors. This will generally solve the immediate problem and also help reduce further corrosion related problems. In older boats where un-tinned wire is frequently found and extensive corrosion of individual conductors occurs, replacement of the entire length of wire with good quality marine grade tinned wire will help ensure trouble free operation. Rich Knowles Nanaimo, BC Boatless but rolling in beer! On Aug 10, 2015, at 20:15, David Knecht via CnC-List <cnc-list@cnc-list.com> wrote: Since I got my boat, I have been bothered by the fact that the engine will not start in the way it is described in the manual unless plugged into shore power. The manual says to hold the glow plug button for about 30 seconds and then while continuing to hold that button in, push the start button. When I do that, the starter does not turn over. If I release the glow plug button and push the start button the engine starts fine. My father (retired electrical engineer) and I (genetic engineer- useless in this case but sounds good) spent some time trying to diagnose the problem this weekend and found two interesting things: 1. The buttons both tested fine in terms of their switch function. We then tested power at the engine. There is a heavy red cable coming from the battery to the starter measured 12V. The red-yellow wire from the start button is attached to what I am presuming is the solenoid (the wiring diagram in the manual does not show a solenoid). We only measured 8 volts at the solenoid when the button is pushed, but 12 volts everywhere else. So that probably explains the fact that both the glow plugs and starter won’t work at the same time because we appear to be losing 4 volts in the solenoid. I will pull the starter next winter and have someone test it unless someone has an alternative suggestion. 2. The wiring diagram in the manual (Fig 2 on page 13) shows the power from the key switch coming into the glow plug button and then a wire from the other lead to the start button. The manual shows that wire running from the downstream side of the glow plug switch so that the start button should only be energized when the glow plug button is pushed (as the manual describes). If that were the case, the I would not be able to start the engine with only the start button. Nevertheless, it does start the engine. Tracing the wires, we found that the bridging wire actually came from the hot side of the glow plug switch, so that either button will work independently as both are always powered. What I don’t understand is why you would wire it the other way (as the manual shows) since that would remove the ability to start the engine without the glow plugs (as in an already warm engine). I don’t know if the PO or some yard mechanic made that change or if it is indicated wrong in the manual, so I am curious how other Universal panels are wired. The way it is actually wired makes more sense to me than what is in the manual unless I am missing something. Thanks- Dave Aries 1990 C&C 34+ New London, CT <pastedGraphic.tiff> _______________________________________________ Email address: CnC-List@cnc-list.com To change your list preferences, including unsubscribing -- go to the bottom of page at: http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
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