Yanmar YSE wiring questions, missing blue wire

[MarkVatcher]

I've got an old PaceShip PY26 with a Yanmar YSE12 that i bought late in the season last year as an experience building boat and boy what an experience so far. It's my first keel boat and the motor has never failed me and all in all it sails great, just needs a fair amount of TLC.

So i'm on to the wiring now. had a diesel mechanic do a tuneup on it and he says the motor is in great shape except for the wiring. seems like one of the previous owners did some DIY wiring so it's kinda messy but the biggest concerns are the Alternator does not seem to be charging at full potential, but i've never had a dead battery, and there is no wire between the alternator and starter which the mechanic says there usually should be.

Also the warning lights don't seem to work, for example the Charge light should come one (exciter?) before starting but does not. Bulb is good because mechanic jumped it and it light up but he said it was backwards. unfortunately i forget if he said he jumped it to positive when it should be negative or visa versa.

It's also got, what i believe to be, and aftermarket Instrument panel with Oil pressure, Engine Water Temp, and Ammeter but i don't believe the oil pressure gauge will ever work because the sending unit is a switch and not a meant for a gauge. not sure if the water temp gauge is the same or not but there is no warning light for water temp.

So i spent a cold rainy sunday afternoon documenting the wiring and comparing it to the manual which has a very basic wiring diagram and it seems like there is a Blue wire that i believe was at some point connected to the starter solenoid but it's been cut at the both ends and no diagram actually shows where it goes. the starter side is cut right at the cable harness wrap and it then runs to the 6 pin connector which should connect it to the control panel but it's been removed entirely from the other side of the connector.

There is however a DIY red wire running from the starter to the Ammeter so i am wondering if this is possibly the replacement for the missing blue cable. Also the Blue wire from alternator A to Regulator A has a DIY red wire spliced in that also runs to the Ammeter. so i'm confused.

I have recently purchased Don Casey's sailboat electronics simplified and trying to compare the "alternator terminal designations" with my own. I have a E (Ground black wire), F (Field red/white wire), But is my N (light brown wire) for the tachometer which i don't have, And whats my A (blue wire between Alternator and Regulator) ? One of them has to be my Sense and the other my output??

I can't see any model numbers on the alternator and i have not yet tested to see if this is a P or N type, anyone know?

I have attached the basic wiring diagram from the manual and my 'work in progress' wiring diagram. anyone that can give me an opinion i would love to hear it.

Thanks.

[transmitterdan]

Nice diagram. Where is the wire between battery minus and engine or starter case? I don't see that on the diagram. It must be there for the engine to start.

[Wrong]

Is your alternator regulator external or internal?

Regarding there being no wire between the alternator and starter. This is going to be the alternator output, commonly referred to as "B" for battery and is denoted by a plus sign. This wire does not have to go through the starter, which is simply a shorter route back to either a battery positive lug or "common" connection at the battery on-off switch. So, your alternator 'output' wire runs to one of those instead of the through the starter. Just because you have no tachometer does not mean the alternator doesn't provide for one.

The red wire between the alternator and ammeter is most likely the sense wire. The other red wire is most likely between the battery and ammeter.

The connection between your alternator and panel light appears to be missing in the mix. Do you see a blue wire coming from the panel back? If so, and you also see a blue wire entering the wiring shroud nearest the engine, check for continuity between there and somewhere on the blue wire - at a terminal or by revealing a bit of wire by cutting away a bit of wire sheathing - at the panel. If you have continuity than the blue wire is most likely the light wire requiring connection to the appropriate alternator plug or terminal. Probably shared with a double type spade connector. The tachometer is normally supplied from a single spade connector on Yanmar type alternators. I'm guessing there's a "T" type double spade connector with a red/white sensor wire and (missing) "light" wire in your case coloured blue.