NASA BM1 oddity

[Scubadoo]

Recently I have noticed that when I press the V/A button to light up the amp display, it gains about 0.4amps, but reads accurately when the button isn't touched. I've had this unit for quite a few years and has been fine until now. The only thing I wonder is that I changed the leisure battery earlier this year, but I can't see how this would affect it as it reads accurately if not touched. I did do a search on this forum but couldn't find anyone with the same issue (or I missed it). Any thoughts what it might be?

 

[pvb]

Recently I have noticed that when I press the V/A button to light up the amp display, it gains about 0.4amps, but reads accurately when the button isn't touched. I've had this unit for quite a few years and has been fine until now. The only thing I wonder is that I changed the leisure battery earlier this year, but I can't see how this would affect it as it reads accurately if not touched. I did do a search on this forum but couldn't find anyone with the same issue (or I missed it). Any thoughts what it might be?

Won't the backlight use power, so there should be a difference in the current reading? 0.4A sounds a lot for a backlight though.

 

[Scubadoo]

Won't the backlight use power, so there should be a difference in the current reading? 0.4A sounds a lot for a backlight though.

I agree BUT this is showing a gain/charge of 0.4amps not a discharge of 0.4 amps.

 

[pvb]

I agree BUT this is showing a gain/charge of 0.4amps not a discharge of 0.4 amps.

Nasa, innit?

 

[wiggy]

Mine went all weird every time I pressed any button, often the voltage reading well below expected. I phones NASA and they advised cleaning alt he contact at the battery, I did and all is now fine.

 

[VicS]

I agree BUT this is showing a gain/charge of 0.4amps not a discharge of 0.4 amps.

Maybe you have disturbed the wiring for the monitor around the shunt .Check and double check especially the black and white wires

 

[Scubadoo]

Thanks vics and wiggly, will double check the connections, from what I remember all the contacts were clean.

 

[Graham376]

My BM1 shows 0.01 drop when I switch the light on but can't remember whether that's amps or volts, not on board to check.

 

[VicS]

Thanks vics and wiggly, will double check the connections, from what I remember all the contacts were clean.

Any chance that you disconnected any of the wiring and reconnected it wrongly.
I must admit I cannot explain an apparent charge of 0.4 amps. Although I cannot confirm it for the BM the lighting for other Nasa Clipper instruments that I have found a figure for only use 25mA

 

[Scubadoo]

Any chance that you disconnected any of the wiring and reconnected it wrongly.
I must admit I cannot explain an apparent charge of 0.4 amps. Although I cannot confirm it for the BM the lighting for other Nasa Clipper instruments that I have found a figure for only use 25mA

Hi vics, I'm pretty sure it was connected back correctly, but of course will double check. It was a simple battery swap so the only bm1 connections on the battery was the red wire and the normal positive and negative connections.

 

[pvb]

I must admit I cannot explain an apparent charge of 0.4 amps. Although I cannot confirm it for the BM the lighting for other Nasa Clipper instruments that I have found a figure for only use 25mA

From his OP, it would sound like he has a BM1 Compact version, rather than the Clipper.

 

[VicS]

Hi vics, I'm pretty sure it was connected back correctly, but of course will double check. It was a simple battery swap so the only bm1 connections on the battery was the red wire and the normal positive and negative connections.

Should not have caused a problem then. Had to ask incase you disconnected any of the black , white or yellow wires

 

[Yngmar]

Recently I have noticed that when I press the V/A button to light up the amp display, it gains about 0.4amps, but reads accurately when the button isn't touched. I've had this unit for quite a few years and has been fine until now. The only thing I wonder is that I changed the leisure battery earlier this year, but I can't see how this would affect it as it reads accurately if not touched. I did do a search on this forum but couldn't find anyone with the same issue (or I missed it). Any thoughts what it might be?

Ours does the exact same and has since I owned the boat. After some initial attempts at trying to troubleshoot this, checking the wiring and replacing the shunt (for unrelated reasons), I contacted NASA and got told to check the wiring and as that was definitely okay the rest was shrugging. I just left it as it works fine without the backlight. There's a LED lamp at the Nav table right above it anyways

My conclusion is some sort of internal fault or design flaw, but it's not worth replacing the unit since it works fine with the backlight off.

 

[VicS]

From his OP, it would sound like he has a BM1 Compact version, rather than the Clipper.

You are right.

Whats the current consumption of the back light...

 

[pvb]

You are right.

Whats the current consumption of the back light...

I'd imagine even less than the Clipper version! Similar displays usually quote around 35mA for backlighting.

 

[Scubadoo]

Ours does the exact same and has since I owned the boat. After some initial attempts at trying to troubleshoot this, checking the wiring and replacing the shunt (for unrelated reasons), I contacted NASA and got told to check the wiring and as that was definitely okay the rest was shrugging. I just left it as it works fine without the backlight. There's a LED lamp at the Nav table right above it anyways

My conclusion is some sort of internal fault or design flaw, but it's not worth replacing the unit since it works fine with the backlight off.

Thanks for the info, I am beginning to think the same as I'm pretty sure the wiring is still correct and in good condition.

 

[pvb]

Thanks for the info, I am beginning to think the same as I'm pretty sure the wiring is still correct and in good condition.

See post 4.

 

[Andrew_Fitton]

My BM1monitor had the fault of Amp reading going haywire when the backlight was lit. I cured the problem by cutting off the small ring terminal with the black and white wires at the shunt and crimping on a new ring terminal. The Amp reading just needed recalibrating after. I diagnosed the fault by wiggling the black and white wires whilst watching the reading vary on the BM1 monitor. It only took me a couple of years to get round to actually look for the cause of the backlight fault.
I do hope this helps you with your problem.

 

[Scubadoo]

My BM1monitor had the fault of Amp reading going haywire when the backlight was lit. I cured the problem by cutting off the small ring terminal with the black and white wires at the shunt and crimping on a new ring terminal. The Amp reading just needed recalibrating after. I diagnosed the fault by wiggling the black and white wires whilst watching the reading vary on the BM1 monitor. It only took me a couple of years to get round to actually look for the cause of the backlight fault.
I do hope this helps you with your problem.

Thank you, that is very helpful info and will check those wire connections.