Corroded Diode in Vetus control panel.

[Guest]

Hi hopefully somebody can advise me here.
The Diode labelled D10 in my lashed up drawing has corroded away in our Vetus panel. The charging has resumed with a makeshift bodge.
 I can easily solder a diode in, but wondered what type of diode I should use? 
Also what purpose does this diode serve?
Many thanks for any advice.

[MoominPapa]

It's probably to stop the alternator powering the ignition-switched supply via the warning light and resistor when the ignition is switched off. If the engine is controlled by a stop solenoid, the circuit via the light and resistor could be enough to keep it pulled in, and leave the engine running when you turn the key off.

 

Any rectifier-type diode will do. If the current is less than 1A, a 1N4003 or better would be fine. If the current is higher, a 1N5402 would be OK.

 

MP.

 

[Tony Brooks]

Anything that will carry the bulb & resistor current.

 

It is to ensure the alternator does not try to supply the auxiliaries (warning lamps gauges etc.) with the engine on and ignition off. If t did it may blow teh filed diodes that would then be passing higher currents.

 

I think you have some wiring missing because it also ensures a fault in the charging circuit, overheat, or low oil pressure buzzer and warning lamps only indicate the specific fault instead of all three.

[Guest]

53 minutes ago, MoominPapa said:

It's probably to stop the alternator powering the ignition-switched supply via the warning light and resistor when the ignition is switched off. If the engine is controlled by a stop solenoid, the circuit via the light and resistor could be enough to keep it pulled in, and leave the engine running when you turn the key off.

 

Any rectifier-type diode will do. If the current is less than 1A, a 1N4003 or better would be fine. If the current is higher, a 1N5402 would be OK.

 

MP.

 

Brilliant, many thanks for the explanation.. One on order 

50 minutes ago, Tony Brooks said:

Anything that will carry the bulb & resistor current.

 

It is to ensure the alternator does not try to supply the auxiliaries (warning lamps gauges etc.) with the engine on and ignition off. If t did it may blow teh filed diodes that would then be passing higher currents.

 

I think you have some wiring missing because it also ensures a fault in the charging circuit, overheat, or low oil pressure buzzer and warning lamps only indicate the specific fault instead of all three.

Brilliant. Many thanks. 
Yes there is more in the way of diodes before the lamp and the others, as they all feed back to a panel bleeper (that has worked part time from new  )
I was just concerned with this D10 as it has corroded away. 
I was warned not to wire a split charge relay on the D+ circuit by the engine fitter (now many years ago,) and wonder if this is the reason?

[WotEver]

8 minutes ago, catweasel said:

I was warned not to wire a split charge relay on the D+ circuit by the engine fitter (now many years ago,) and wonder if this is the reason?

Possibly, but a VSR is a far superior solution anyway. And these days they’re inexpensive. 

[Guest]

1 minute ago, WotEver said:

Possibly, but a VSR is a far superior solution anyway. And these days they’re inexpensive. 

Agree 100%.  I took some abuse on here in about 2004 for fitting a VSR, but have never regretted it. 

[WotEver]

6 minutes ago, catweasel said:

Agree 100%.  I took some abuse on here in about 2004 for fitting a VSR, but have never regretted it. 

Ahh well, they were expensive in 2004

 

[Guest]

10 minutes ago, WotEver said:

Ahh well, they were expensive in 2004

 

Very true it was, and it was a two part system too. Served me well and worth every penny though. It seemed that I was going to burn in hell for fitting one. 

[dor]

The opposite can happen as well, where the diode conducts in both directions.  This leads to the engine start battery discharging when everything is turned off.

[Guest]

Just a bit of feedback:
I received the diode from fleabay today (3A one as recommended by Moomin Pappa) and soldered it in place of the temporary link. All seems well and everything behaving as it should.

Many thanks for advice given on here, and especially to those who sent diagrams, advice etc.