New voltage converter not compatible with existing ignition switch

[CorkBouy]

I recently had to change out the voltage converter on my Volvo Penta D4 260hp engine as I had a reverse polarity problem that blew the original one out.
The new voltage converter that I got from Volvo is for the newer model of D4 engine and while it works fine it is not compatible with the existing ignition switch. Now when I turn on the ignition to the on position the engine fires up without turning the key fully to the right and once started I then need to turn the key back to the 0 position to get the instruments to become live.
While this will work in the short term, it is not ideal as I cannot trim the engine while the boat is out of the water unless I start the engine.
Has anyone had a similar experience and would anyone know if is possible to reconfigure the existing ignition switch?

 

[alt]

Send it back to Volvo and get the proper item, surely?

 

[spannerman]

I am a bit puzzled as the DC to DC converter just gives a stable supply to the ECU so its not affected by voltage variants in the system. I’ d be more worried by your reverse polarity problem that did the original damage, has it damaged any other components in the ECU network? i.e. the PCU which controls the trim and gear shifting.

 

[jrudge]

I was thinking the same but given I have never tried to look at how a boat ignition works ( I rather assumed I knew the principal) I thought I would keep my fingers to myself.

Engine on - so it is triggering the starter motor
0 - live

It rather sounds like a faulty / shorted switch. The Switch just tell wires what to do.

When it goes to start it will energise the solonoid.

It is quite plausible that is just talks to the ECU as opposed to direct to starter etc, but I would still suspect the switch or a stray wire near the ignition that is sending erroneous signals.

 

[Andyroonot]

On the back of the ignition barrel there are 4 wires-red, red/blue, red/yellow & purple
Red becomes live with battery +ve when the system (inc. DC-DC converter) is live, and is supplied via the HCU. Position 1 switches red to red/blue & prompts the HCU to send a CAN signal to the rest of the system to wake up inc the gauges. Injectors can then be heard ‘ticking’
Position 2 (cranking) then switches red to red/yellow, which prompts the HCU to send a crank CAN signal to the ECU which triggers the starter motor to engage
Whilst red to red/yellow is switched, red/blue becomes open circuit so there is a diode linking the two that keeps red/blue live until the key springs back to position 1.
If the engine is cranking as soon as position 1 is selected then either the HCU is playing up or the diode is the wrong way around. Or the key switch could be faulty I guess?
But I can’t see how a DC-DC converter would cause that, as all it does is take a positive from the batteries and split it to the EVC system & engine ECU to provide stable power, not a crank signal/voltage

 

[jrudge]

Excellent explanation. I would think the diode has gone as then there would be a direct link between live and start.

 

[Alicatt]

Not for one minute do I think this is the problem.
On my 1998 Toyota Landcruiser it had the cold weather pack which entailed twin batteries and split charging, just like on boats one battery was for the engine and the other for house keeping or auxiliary, when switching the ignition from ON to Crank there was a heavy relay that disconnected the house keeping etc. and switched the batteries from parallel to series and supplied 24V to the starter motor, gave great starting summer and winter. There was one step further you could go with an option for a block heater that kept the oil liquid in extreme cold environments you could get it in 120V or 240V AC and you just plugged it in to the mains.
I had the aux battery hooked up to an inverter to run video equipment, which was why the car was specified with the cold pack.

 

[jrudge]

Which is all fine but how does this relate in any way to the ops issue ?

 

[Alicatt]

Which is all fine but how does this relate in any way to the ops issue ?

I don't think it does, but reading Andyroonot's message reminded me of an alternative that is used in some electrics and engine starting systems on a diesel powered vehicle.
Not had that car in almost 20 years now

 

[CorkBouy]

I am a bit puzzled as the DC to DC converter just gives a stable supply to the ECU so its not affected by voltage variants in the system. I’ d be more worried by your reverse polarity problem that did the original damage, has it damaged any other components in the ECU network? i.e. the PCU which controls the trim and gear shifting.

Everything seems to work fine once fired up. The guy that fitted the new one says the older ignition switch is not compatible with the new converter.

 

[CorkBouy]

I was thinking the same but given I have never tried to look at how a boat ignition works ( I rather assumed I knew the principal) I thought I would keep my fingers to myself.

Engine on - so it is triggering the starter motor
0 - live

It rather sounds like a faulty / shorted switch. The Switch just tell wires what to do.

When it goes to start it will energise the solonoid.

It is quite plausible that is just talks to the ECU as opposed to direct to starter etc, but I would still suspect the switch or a stray wire near the ignition that is sending erroneous signals.

Thanks jrudge I will try and have that checked out.

 

[CorkBouy]

On the back of the ignition barrel there are 4 wires-red, red/blue, red/yellow & purple
Red becomes live with battery +ve when the system (inc. DC-DC converter) is live, and is supplied via the HCU. Position 1 switches red to red/blue & prompts the HCU to send a CAN signal to the rest of the system to wake up inc the gauges. Injectors can then be heard ‘ticking’
Position 2 (cranking) then switches red to red/yellow, which prompts the HCU to send a crank CAN signal to the ECU which triggers the starter motor to engage
Whilst red to red/yellow is switched, red/blue becomes open circuit so there is a diode linking the two that keeps red/blue live until the key springs back to position 1.
If the engine is cranking as soon as position 1 is selected then either the HCU is playing up or the diode is the wrong way around. Or the key switch could be faulty I guess?
But I can’t see how a DC-DC converter would cause that, as all it does is take a positive from the batteries and split it to the EVC system & engine ECU to provide stable power, not a crank signal/voltage

Thank you Andyroonot, I will try have an auto elec check this out and see if he can find the diode.

 

[Andyroonot]

Thank you Andyroonot, I will try have an auto elec check this out and see if he can find the diode.

It’s an orange, slim rectangular block of plastic that is (should be!) immediately after the terminal for red/yellow wire, so very close to the back of the ignition barrel. It’ll probably be cable tied to the loom so you can’t really miss it