Vovlo MD6A dynastart

[Ian_Edwards]

A fellow boat owner has a fault on the dynastart on a MD6A.
The engine turns over, but will not start.
There's a good 12 volts at the key switch before starting, an no voltage on any of the dynastart terminals.
Turning the engine over, there's about 8 volts on the starter and 8 v and 6v on the other 2 terminals, the dynamo output is getting hot.
Disconnecting the dynamo output, and the engine starts.
It looks like the dynamo output is shorting either through the control box, or (less likely) through the dynastart.
I couldn't get at the silver control box today, it's under the cockpit floor, perhaps tomorrow.
Any ideas on what's wrong?
Can anyone point to a circuit diagram of the silver control box.
Cheers
Ian

 

[Bilgediver]

Sounds like a relay not behaving. There a is some info here.


Old Marine Engine: Bosch Dynostart wiring

 

[Ian_Edwards]

I noticed that the charging light bulb has blown, in fact the glass is broken.
The bulb is in series with the with the D+ terminal.
Does the absence of the chrge bulb have any effect on this problem?

 

[Bilgediver]

I noticed that the charging light bulb has blown, in fact the glass is broken.
The bulb is in series with the with the D+ terminal.
Does the absence of the chrge bulb have any effect on this problem?

I doubt it I would expect the dynostart would bebe configured for starting and the charging circuit disconnected. It is a Bosch system and the control boxes may still be available.I


Here is an alternate.

12V Dynastart

 

[Ian_Edwards]

I got it working, a relay contact welded to one side, opened it with a small screwdriver, cleaned (of sorts) with very fine wet and dry. The relay was permanently connecting the battery to the D+ terminal on the dynamo.
It works for now but needs a new one. Looks like the origin, probably 50years, or so, old.
Many thanks to Bilgediver for his help, and the links, which allowed me to workout the most likely fault.

 

[coopec]

I'd agree with Bilgediver that it could be a solenoid playing up.
I know when I set my starting mechanism up I had to have a solenoid for the starter and also a solenoid (a car door solenoid in my case) to work the fuel mechanism. (Maybe that is the one not working?)

 

[Ian_Edwards]

Now looking for a wprking replacement.
The orginal unit does not look it can be refurbished. All the components are spot riveted.

 

[VicS]

Now looking for a wprking replacement.
The original unit does not look it can be refurbished. All the components are spot riveted.

New ones are solid state electronics, A separate "solenoid" (relay) is used for the starter function