VP MD20XO Basic Control Panel Fault

[TSB240]

Basic Control Panel

The Facts
Had the alarm trigger on the panel last weekend with every alarm light on whilst engine running.
Engine had been lightly used.
I could hold my hand on top of heat exchanger.
Alternator was kicking out a good voltage and there were no new knocking sounds indication a sudden loss of oil pressure.
Rev counter working fine.

Anchored up for the night for a drink and a think..

In the AM Turn Panel illumination light on with cold engine.
Instant alarm but only the High temperature light showing.
Push two way switch for preheat no alarm and preheat relay working fine and engine started fine.
Alarm returns as soon as release two way switch.
Now every alarm light on panel whilst engine running.

Disconnected alarm and ran engine for the best part of an hour and a half at or near max revs until returned to dock confident that I just have a sensor or wiring fault.



I am assuming that there must be a path to 0v on wire 3 Brown/White.

My first check will be to eliminate a faulty temperature switch.

Is it possible for them to fail permanently closed as I assume this is normally open?

Should this not be the cause I am open to any other suggestions as to where to look for a short to earth. Other peoples experience of the MD 20X0 series is very welcome.

NB saildrive model so engine is isolated from earth.

Other Info:-
I recently replaced the exhaust elbow so some small disturbance of the relay box and engine loom connector. The relay box was just unbolted but no electrical connections were undone other than removing and replacing the single retaining screw that holds the multi-fuse pack to the front of the black relay box.

Thanks in advance
Steve

 

[Ruffles]

What would happen if the 0v connection to the engine was loose?
Whatever has gone wrong it is affecting all sensor circuits.

 

[VicS]

Thanks for posting that diagram... its easier to follow than the ones in the owners manuals.

I would definitely try disconnecting the temperature sensor but if that does not identify the problem you have to consider the possibility of a short in the wiring. You should be able to measure 12 volts on the brown / white wire. If you cannot it may indicate such a short

 

[TSB240]

It's definitely not the sensor same problem if disconnected. Checked with meter switch is open. I am getting 6V on the lead when disconnected.

 

[RIBW]

Thanks for posting that diagram... its easier to follow than the ones in the owners manuals.

Vic, Thought I would jump in to clarify that this diagram is one I personally modified to reflect the customisation I have done to my VP2003 and should not be taken as universally valid. You will see that I have rewired the panel and loom to use the 4th lamp (Normally unused - No Glowplug on the VP200X engines) to give me a raw water coolant flow alarm. Having said that, everything to the left of that 4th lamp should apply to most VP200X engines. I have no idea if it is valid for Steve's VP20X0.

I would definitely try disconnecting the temperature sensor but if that does not identify the problem you have to consider the possibility of a short in the wiring. You should be able to measure 12 volts on the brown / white wire. If you cannot it may indicate such a short

As Steve has tried disconnecting the sensor and is measuring 6V, I agree with you about the short (subject to the 20X0 panel being similar to the 200X panel wiring).

It is also worth checking that the coupling rings (at both ends of the loom) are tightly screwed on and the mating halves of the connectors firmly 'home'.

Cheers
Bob

 

[VicS]

Vic, Thought I would jump in to clarify that this diagram is one I personally modified to reflect the customisation I have done to my VP2003 and should not be taken as universally valid. You will see that I have rewired the panel and loom to use the 4th lamp (Normally unused - No Glowplug on the VP200X engines) to give me a raw water coolant flow alarm. Having said that, everything to the left of that 4th lamp should apply to most VP200X engines. I have no idea if it is valid for Steve's VP20X0.

Thanks to you for drawing it.
I wondered about the 4th light but I know its the glowplug indicator on MD20X0 and other engines with glowplugs ( exact wiring varies). Apart from this is appears to be the same as all the panels for all versions of the 20X0 engines that I have compared it with. Steve's engine must be an early one having a isolated DC system

As Steve has tried disconnecting the sensor and is measuring 6V, I agree with you about the short (subject to the 20X0 panel being similar to the 200X panel wiring).

Yes I saw that last night ... Still wondering why he found 6V........ ??

It is also worth checking that the coupling rings (at both ends of the loom) are tightly screwed on and the mating halves of the connectors firmly 'home'.

Cheers
Bob