Strange Nasa BM1 problem

**Playtime** · 03-01-11, 17:45

Originally Posted by pieter2

@Playtime: I have read the voltages on the terminal black, just behind the BM1 display, So where the wires black and white are NOT connected with eachother!
See photo below. On the shunt the black and white wire are connected with eachother in one crimp.

OK then it is fairly obvious that somewhere in the circuit the black and/or white wires are not connecting as they should.

As suggested before, please check the single crimp where the black and white wires connect to the shunt.

Secondly, double check the connector block shown in your photo - maybe one of the wires is not actually connecting properly here, for example, you may have screwed into the insulation and not the wire. This is quite easy to do and looks like a good connection when in fact there is no connection.

Good hunting

**pieter2** · 03-01-11, 17:47

Please look at answers below

Originally Posted by Playtime

OK then it is fairly obvious that somewhere in the circuit the black and/or white wires are not connecting as they should.

As suggested before, please check the single crimp where the black and white wires connect to the shunt.
THIS I WILL DO ASAP

Secondly, double check the connector block shown in your photo - maybe one of the wires is not actually connecting properly here, for example, you may have screwed into the insulation and not the wire. This is quite easy to do and looks like a good connection when in fact there is no connection.
THIS I ALREADY DID (TWICE).

Good hunting

**VicS** · 03-01-11, 19:34

As suggested before, please check the single crimp where the black and white wires connect to the shunt.

This is beginning to look more and more likely to be the place where the trouble lies. One of those wires is the negative power supply to the BM1 and a bad connection will give rise to a small voltage accross the connection. I think this would show up as a charge current being displayed.
We are looking for something that gives a reading of 3amps. IIRC the shunt is 50mV per 100amps so were are only looking for 1.5 mV
Earlier we were looking at 1.2 mV between yellow and white/black when there should have been zero.

Is this it ?

I'd clean and remake the connection between the crimp and the shunt and then if that did not solve the problem I would cut off the crimp and remake it or even solder the black and white wires onto a suitable ring terminal.

(Crimped terminals I dont like! I hear all the objections to soldered connections but done properly you get a 100% good connection!)

**pieter2** · 03-01-11, 20:58

Someone noticed a mistake in the schedule as given by me, some posts earlier. It does not interfere with the problem of the NASA, but just in case someone would use the schedule at some time for other purposes, here you have a more correct version (connections with relay / loading lamp are changed)
I will keep you informed about the new black-white connection!

**VicS** · 03-01-11, 23:15

Originally Posted by pieter2

Someone noticed a mistake in the schedule as given by me, some posts earlier. It does not interfere with the problem of the NASA, but just in case someone would use the schedule at some time for other purposes, here you have a more correct version (connections with relay / loading lamp are changed)
I will keep you informed about the new black-white connection!

Yep you have corrected the warning light ( "loading lamp") to alternator connection and the alternator output to the split charge control relay but your representation of the engine starter circuit is a bit over simplified.
It was the engine start button and loading lamp that caught my eye. PVB's too I imagine.

Don't forget that the connection of the starter battery negative and the autopilot ( "steering machine") are still incorrect.

Below shows how the start battery negative and the autopilot negative should be connected

**pvb** · 04-01-11, 08:16

Originally Posted by VicS

Below shows how the start battery negative and the autopilot negative should be connected

I'd still suggest the autopilot positive should be on the switched side of the main switch.

**VicS** · 04-01-11, 12:42

Originally Posted by pvb

I'd still suggest the autopilot positive should be on the switched side of the main switch.

Diag modified !

**lula6894** · 06-01-11, 19:27

Hi all,
To add more information: I have checked today all the installation and I can afirm that the stratnge 3A also appears when the loads are applied, the charger working and the boat in normal situation. If light ON in the NASA BM1 is pressed there is a change of the current showed by it in 3A (charging).
I hope this help and somebody found a solution.
Cheers

**VicS** · 06-01-11, 20:34

Perhaps someone will print out this thread and take it with them to the boat show.
Nasa stand A29

**VicMallows** · 09-01-11, 16:56

I've been on my boat today, and one mission was check some of these weird reported happenings.

My batteries had been fully isolated, and even the BM-1 disconnected (as I don't like the small drain over several months). On reconnecting the BM-1 I was rather surprised to see the domestic battery bank showing 11.1v ...NOT GOOD ... although not impossible as 3yrs old and sometimes they can die a sudden death especially in the cold we've had.

However when they happily started the Eberspacher (engine not yet started), and then on charge dropped to a charge acceptance of 3A in a few minutes (at 14.8v) something was obviously fishy! I then tried PIETER2 's thing of turning the backlight on and off. The indicated voltage varied all over the place (though I didn't observe any change in current or AHr indications.)

It only took a couple of minutes and a decent test meter to determine that the problem was the inline fuseholder in the red (permanent) feed to the battery +ve. (the spring-loaded type are notoriously unreliable at both high and very small currents......I will replace with an inline blade type).

Not quite the same symptoms as PIETER2, but something to watch out for if you get strange readings.

Vic