Bukh instruments and alarm intermittent

[LittleSister]

New to me Bukh 36. Engine starts and runs fine.

Last week had first run with the engine, the instruments (revs, temp, oil pressure, fuel) were working (as they had been previously when the boat was ashore). Today the instruments didn't come on (but the engine ran anyway). When the key is turned on and off there is a slight kick in the fuel gauge needle, so something is connecting to something. The charge and oil pressure warning lights do come on (until the motor is started).

We were guessing that maybe there was an earth return not connecting, but did not have a manual or wiring diagram with me. There is definitely 12v +ve at the back of the 'distribution board'. We waggled and cleaned as best we could the two engine wiring loom connector blocks at the rear of the engine wiring loom to no avail.

Possibly related, but possibly not: I realised after the engine first run that I could not remember the alarm sounding before the engine was started and when it was switched off, so thought to consciously check it today. It did not sound. Strangely, while we were later switching the ignition on and off trying to sort the instruments it did sound a couple of times, then was silent again.

Any suggestions? (I have read that the distributor board and ignition switch barrel can give problems, so I am suspicious of these.)

 

[Saltram31]

Had a similar problem on my DV20. Remove the spade terminal from the thermostat sensor and contact it with bare metal on the motor with the ignition turned on. If the alarm sounds, the threads on the sensor, and thermostat housing alan bolts need to be cleaned up so proper grounding is made.

 

[Moonbeam]

Not sure if you have the same electrical connector block (as circled in pic) as our DV24? but if so, check if the zip tie holding them together has come off. Ours had, there is no other locking method to keep these two blocks together and our engine failed to start one time as these blocks had vibrated loose. Just a thought, obviously, it could be a loose connection elsewhere.

 

[LittleSister]

Thanks for the suggestions. Still looking for answers, so any more ideas would be welcome.

Remove the spade terminal from the thermostat sensor . . . .

I'll put that on the list, but i would have thought even if the temp connection were no good, the alarm should sound due to lack of oil pressure, electric charge, etc.- so alarm issue perhaps more likely to be the 'distribution board' rather than the individual sensors.

Not sure if you have the same electrical connector block (as circled in pic) as our DV24?

The two connectors at the rear of my engine are a little different, but we did try moving them about, unplugged and replugged them to see if that made a difference, and then cleaned up the contacts as best as we were able and tried the same again without success.

 

[LittleSister]

I finally found the culprit for the intermittent alarm the other day, so thought I'd report back.

It was the distributor board - the terminals on the back of the board (to which wires from ignition switch etc. are connected) are sort of riveted to those on the other (hidden) side of the board on which the diodes and other components are mounted. The 'rivet' connection between the two sides of one terminal (at least) is physically poor and electrically intermittent.

I have temporarily cured the problem by forcing the inner and outer parts together using the end of a marlin spike. One day I'll solder the two sides together through the hole, or by using and link wire from one side to the other. application of forcing the 'rivet' against the terminal.

The lack of instruments had turned out to be duff connection ( -ve, IIRC) on the back of the ignition with, caused by that particular connector fouling, and being partially dislodged by, part of the woodwork underneath the instrument panel when it is in place (wasn't obvious when panel is raised to view connections on the back of the panel).