Engine Extractor Runs Briefly at Night

[PaulRainbow]

Paul, My very rudimentary, back of a fag packet, take of the system from the description. ? marks denote cables that have the destination or origin unknown. No idea of the split charge system, how or where it is connected. Similar for Domestic. Would you agree with this? Maybe some of the other experts could comment!

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Looks about right from what we've been told, but a lot of ???s

Leaving the negative isolator on would narrow it down considerably, probably even cure the problem.

 

[Alex_Blackwood]

I would still like to know what sort of 12v relay will energise at 1.7V.

I wouldn't take that as "Gospel" too many unknowns and possible "fish of a Crimson hue"

For Paul, Thanks for response. Not sure how leaving the negative on would help, you are the expert on that. Whatever is going on he must be getting a circuit, + &- ve from some where, at around 12volts. I still suspect a capacitor getting a charge, triggering the relay and discharging. If all the engine +ve's & -ve's are isolated. Where from. As I said originally. On site investigation only answer!

 

[Paulfireblade]

Hi all, Apologies for the delay as I have been away but just been back to boat and thought you might be interested in outcome.

 

[Paulfireblade]

Anything stray coming from galvanic protection somehow?

I have a Galvanic Isolator so everything tests okay from that area but worth checking

 

[Paulfireblade]

They have improved, by fitting VSRs instead of diodes. Yours will almost certainly have a diode pack. I don't recall a diode pack ever doing what you describe, but still worth checking. Look for something like one of these :

split charge diode - Google Search

Having investigated charge circuit, no VSR but a 60 amp relay that connects the engine and leisure batteries instantly there is sufficient voltage coming out of the alternator. Having checked Jeanneau wiring diagram that was factory fitted.

 

[Paulfireblade]

** If i may, DC power doesn't have live or an Earth. It has positive and negative. The only Earth on a boat is the AC Earth, an Earth bonding circuit etc.

Apologies for using the word "Earth" no wish to offend anyone but I am sure you are aware of the phrase "bad earth" in connection with vehicle 12 volt DC battery circuits and the strange faults that can occur especially with rear light clusters and is that I had in mind when I reference Earth in my post so apologies for any confusion.

 

[PaulRainbow]

Having investigated charge circuit, no VSR but a 60 amp relay that connects the engine and leisure batteries instantly there is sufficient voltage coming out of the alternator. Having checked Jeanneau wiring diagram that was factory fitted.

That is a VSR then Paul. Voltage Sensing Relay.

 

[Paulfireblade]

Size of normal relay? fair enough (I have fitted one to a conversion I did about 20 years ago but couldn.t remember how big it was or what it looked like.)

I think I will replace with a nice new one but keep the old one as a back up. thank you, for letting me know.

 

[Paulfireblade]

Bingo!!!!!!

The OP also mentions "two pole battery isolators for the engine " in post #1. His boat would not have been built with double pole isolators, it would have had positive isolators for each battery/bank and a common negative isolator.

The Negative isolator under companionway is labelled to be turned on for Engine along with positive isolator, this information was also reinforced by previous owner when we went on Test Sail.

 

[Paulfireblade]

There is not a double pole isolator, but there is an isolator that only isolates the engine negatives. As i said earlier, that's not how the boat would have been wired from new (at least i have never seen a Jeanneau wired that way). The negative isolator would have isolated all negatives.

You are correct that this arrangement could cause issues. It would be worth the OP turning the engine positive off, but leaving the negative on, see if that "cures" the problem.

Regardless, i would either, connect all negatives to the switch, or connect them all to a terminal post (or bolt them together) and connect the now redundant switch to the load terminals of the engine and domestic isolators to be used as an emergency parallel switch.

Totally correct and the wiring diagram confirms that the negative isolator disconnects all negatives and that is how it is still wired so the labelling is incorrect and amazingly previous owners have been using the boat this way

 

[Paulfireblade]

My money is on a bad earth somewhere causing a reverse flow through the relay coil.

I'm slightly disturbed by this talk of a double pole isolator - given that the normal way to wire the DC on a boat is with both house and start batteries sharing the negative, introducing something that isolates the *negative* side of the system is likely to cause all sorts of stray currents!

Amazing anything in the living section worked at all What a trip the negative return journey was

 

[Paulfireblade]

I would still like to know what sort of 12v relay will energise at 1.7V.

Fairly standard Hella relay but the more load going through the switch panel with the Negative Isolator turned off the higher the voltage increased to. I saw around 1.7 volts with main LED lights and Fridge running, if a few extra cabin lights were on and water pump ran it would have gone higher but still less than I would have expected to be sufficient for a 12 volt relay to switch.