Engine Extractor Runs Briefly at Night

[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

Thank you, for the link. I have not seen anything that sophisticated in my engine bay or adjoining battery box, about the only item I can think of that I am not sure what it does in that area is what looks like an old metal cased relay.

My boat has three Gel house batteries, I remember reading somewhere that Gel batteries need a different charge system to Lead acid batteries or have I got that wrong?

 

[PaulRainbow]

Thank you, for the link. I have not seen anything that sophisticated in my engine bay or adjoining battery box, about the only item I can think of that I am not sure what it does in that area is what looks like an old metal cased relay.

They are not really sophisticated Paul. Try following the thick cable from the alternator, where does it go ?

Pic of the "relay", preferably showing the wires to it too ?

My boat has three Gel house batteries, I remember reading somewhere that Gel batteries need a different charge system to Lead acid batteries or have I got that wrong?

Gel, SLA and AGMs can all use a profile that meets the needs of each type.

 

[Paulfireblade]

They are not really sophisticated Paul. Try following the thick cable from the alternator, where does it go ?

Pic of the "relay", preferably showing the wires to it too ?



Gel, SLA and AGMs can all use a profile that meets the needs of each type.

Thank you, I will follow that advice. Many thanks

 

[Alex_Blackwood]

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

Even if the alt. was connected directly to a battery there is no way it should be able to connect to the system.

 

[PaulRainbow]

Even if the alt. was connected directly to a battery there is no way it should be able to connect to the system.

"Should" being the key word.

Doesn't matter if the OP has a diode, VSR or B2B, it should be connected to the battery side of the isolator, so it should not be possible for a fault with either to do what the OP describes.

The OPs boat would almost certainly have been built with a diode pack for split charging, but I think split charging is a Red Herring.

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.

If the negative and positive were both isolated that should rule out a lot of things, but i'm not convinced that the negative is being isolated, perhaps the OP could confirm this and say how it is being isolated ?

The relay coils seems to be triggered by stray voltage from the engine ECU, where does it get the negative also required for the coil to trigger, if the negative is isolated ?

If the fan powers up, where does the input positive to the relay contacts come from, if the positive isolator is open ?

I very much doubt the OPs boat was fitted with an engine room fan from new, it just shouldn't need one. Connecting the relay to the ECU is an extremely bad idea. If i was the OP, i'd disconnect the relay from the ECU and confirm the fan is a pointless waste of time and energy, then either leave it disconnected or remove it.

 

[Alex_Blackwood]

"Should" being the key word.

Doesn't matter if the OP has a diode, VSR or B2B, it should be connected to the battery side of the isolator, so it should not be possible for a fault with either to do what the OP describes.

The OPs boat would almost certainly have been built with a diode pack for split charging, but I think split charging is a Red Herring.

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.

If the negative and positive were both isolated that should rule out a lot of things, but i'm not convinced that the negative is being isolated, perhaps the OP could confirm this and say how it is being isolated ?

The relay coils seems to be triggered by stray voltage from the engine ECU, where does it get the negative also required for the coil to trigger, if the negative is isolated ?

If the fan powers up, where does the input positive to the relay contacts come from, if the positive isolator is open ?

I very much doubt the OPs boat was fitted with an engine room fan from new, it just shouldn't need one. Connecting the relay to the ECU is an extremely bad idea. If i was the OP, i'd disconnect the relay from the ECU and confirm the fan is a pointless waste of time and energy, then either leave it disconnected or remove it.

Paul quite agree, I think there may be some info missing. Also if the ECU and fan +ve's come via the ignition switch ???

 

[PaulRainbow]

Paul quite agree, I think there may be some info missing. Also if the ECU and fan +ve's come via the ignition switch ???

The presence of the relay would suggest that the positive supply to the fan (via the relay) would not come from the ign switch, i would expect a fused supply from the main busbar or isolator, the ECU power should be switched via the ign switch though.

Making a few assumptions/guesses, i'd say the negative isn't being isolated (would need at least two separate faults for the symptoms described). Charging should be connected to the battery side of the main isolator, so that shouldn't be the cause.

The voltage is low, so it looks like a "leak" or feedback. I wonder what "always on" circuits exist. Seen some odd faults on dodgy bilge pumps/float switches, for instance.

 

[Alex_Blackwood]

The presence of the relay would suggest that the positive supply to the fan (via the relay) would not come from the ign switch, i would expect a fused supply from the main busbar or isolator, the ECU power should be switched via the ign switch though.

Making a few assumptions/guesses, i'd say the negative isn't being isolated (would need at least two separate faults for the symptoms described). Charging should be connected to the battery side of the main isolator, so that shouldn't be the cause.

The voltage is low, so it looks like a "leak" or feedback. I wonder what "always on" circuits exist. Seen some odd faults on dodgy bilge pumps/float switches, for instance.

Good thinking Batman!

 

[penfold]

If you can't eliminate the stray voltage fault, put a resistor(something over 1000 ohms to minimise current and heat generation) between the relay feed and negative, it will dissipate the stray voltage but allow it to trigger the relay normally.

 

[Alex_Blackwood]

If you can't eliminate the stray voltage fault, put a resistor(something over 1000 ohms to minimise current and heat generation) between the relay feed and negative, it will dissipate the stray voltage but allow it to trigger the relay normally.

Very bad practice. It doen't clear th fault!,

 

[penfold]

Are we delving into VP ECU repair? I'd say that was a bad idea. However unorthodox it will remedy the OP's problem in a way unlikely to cause another problem in its place.

 

[QBhoy]

I’d be suspicious of things in the vicinity that have a constant feed to them. Bilge pump and float switch perhaps. Is there a solar panel fitted ?
has the bilge pump been wired questionably that could allow a feed crossing between the positive feed (for float) and the actual dash switch ? That being the case…is there any under dash link between that and the ignition perhaps ? Strange one.

 

[PaulRainbow]

I’d be suspicious of things in the vicinity that have a constant feed to them. Bilge pump and float switch perhaps. Is there a solar panel fitted ?
has the bilge pump been wired questionably that could allow a feed crossing between the positive feed (for float) and the actual dash switch ? That being the case…is there any under dash link between that and the ignition perhaps ? Strange one.

Wish i'd thought of that, oh, hang on #27

 

[PaulRainbow]

If you can't eliminate the stray voltage fault, put a resistor(something over 1000 ohms to minimise current and heat generation) between the relay feed and negative, it will dissipate the stray voltage but allow it to trigger the relay normally.

You want to put a resistor between the ECU positive and negative ?

Seriously ?

 

[PaulRainbow]

Are we delving into VP ECU repair? I'd say that was a bad idea. However unorthodox it will remedy the OP's problem in a way unlikely to cause another problem in its place.

The only way we'll be delving into ECU repair is if your advice is followed.

It will not remedy the OPs problem, it will just cover the fault up, if it doesn't damage the ECU.

If all he want to do is stop the fan running without actually curing the underlying problem, he can simply disconnect the relay coil trigger wire from the ECU (which i think should be part of the overall fix, stop messing with the ECU). If he wanted to stop it running periodically when it shouldn't, but still work with the engine running, move the relay coil trigger to the ign switch ON (that's where it belongs anyway, if the fan was actually needed).

 

[QBhoy]

Wish i'd thought of that, oh, hang on #27

Not sure how to take that really ! In the spirit of diplomacy and Xmas cheer…I’ll offer my sincere apologies for not noticing you’d said similar. In an effort to appeal to the less abrasive side of your nature, should there be such a thing ! All the best

 

[penfold]

If drawing 50mA kills a relay driving circuit it's not of merchantable quality.

 

[Paulfireblade]

They are not really sophisticated Paul. Try following the thick cable from the alternator, where does it go ?

Pic of the "relay", preferably showing the wires to it too ?



Gel, SLA and AGMs can all use a profile that meets the needs of each type.

Sophisticated was probably the wrong word, but they look like substantial lumps with a built in heat sink, do not recall anything looking like that but I will visit, remove bottom step with isolator switches mounted to it and trace all wiring from Alternator to batteries

 

[Paulfireblade]

"Should" being the key word.

Doesn't matter if the OP has a diode, VSR or B2B, it should be connected to the battery side of the isolator, so it should not be possible for a fault with either to do what the OP describes.

The OPs boat would almost certainly have been built with a diode pack for split charging, but I think split charging is a Red Herring.

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.

If the negative and positive were both isolated that should rule out a lot of things, but i'm not convinced that the negative is being isolated, perhaps the OP could confirm this and say how it is being isolated ?

The relay coils seems to be triggered by stray voltage from the engine ECU, where does it get the negative also required for the coil to trigger, if the negative is isolated ?

If the fan powers up, where does the input positive to the relay contacts come from, if the positive isolator is open ?

I very much doubt the OPs boat was fitted with an engine room fan from new, it just shouldn't need one. Connecting the relay to the ECU is an extremely bad idea. If i was the OP, i'd disconnect the relay from the ECU and confirm the fan is a pointless waste of time and energy, then either leave it disconnected or remove it.

Under bottom step of companionway there are a black and red isolator switch for engine (fairly standard chunky twist 90 degree for off) with both turned off engine wont run but house electric still run so negative isolator presumably for engine only but I need to re-visit and confirm.

The relay takes its earth from the Earth bus and has a permanent fused live feed from engine battery so if that had been wired in to the isolator then the feed to relay would not have a supply so fan would not run.

So it does sound like it has not been wired up very well and as Paul says could be removed altogether but it has alerted me to some stray voltage present in the engine circuit which still needs me to find the cause.

 

[Paulfireblade]

Are we delving into VP ECU repair? I'd say that was a bad idea. However unorthodox it will remedy the OP's problem in a way unlikely to cause another problem in its place.

Definitely don't want to delve in to ECU, engine behaves impeccably but not keen on stray voltage that this issue has made me aware of that is present in engine when isolators are turned off