Bukh DV36 Generator

[petedg]

Went down to our LM30 today and on starting the engine the red “Amp” light does not switch off. I checked the 3 wires on the generator and noticed that the yellow wire had come off the spade terminal. I made a new connection and assumed that would fix the problem but the “Amp” light is still on with the engine running. I also noticed the tachometer seems to be more unsteady than usual. Does anyone have any thoughts what the problem might be or how to check out the generator?
Thanks in advance for your help.

[Brian & Glenda]

Did you increase the engine speed at all, and did the light stay on after you did so? Mine stays on for a few seconds sometimes, until either the voltage regulator picks up that a little charging may be needed and it increases the charge output; or until I give the throttle a small increase in speed above idle (~200 RPM is all that is needed) ... whichever comes first. Once the light goes out, it then stays out even if the engine speed is returned to idle.

(Balmar ARS-5 external voltage regulator on Motorola 90A (if I recall correctly) alternator.)

[petedg]

Thanks for your reply, I didn’t try increasing the speed and next time I go down I will give it a try. Previously it always went off immediately on start up at idling speed.

[petedg]

Increasing the engine speed did not make any difference, the “Amp” light still stays on continuously. Are there any checks I can do now I’ve taken it out?

[petedg]

The saga goes on. I installed a new alternator today which seems to work fine, the “amp” warning light goes to when the engine is started. However, the tachometer and pressure gauge remain on zero and the water temp reads full scale in the red. I’m wondering if there is some sort of grounding issue? Any thoughts would be appreciated.

[tonyp]

I don't know if this will be of any help, but the tacho, water temp and oil pressure gauges are usually all connected to a different wiring loom to the oil, water and charge lights. The two looms go to two large multi-plug and sockets. On our DV24 these are on the side of the engine block. Is it possible that one of these plugs has been slightly dislodged from its socket? I'd suggest pulling both multi plugs from their sockets and re-fitting them, just in case. The tacho should be operated by a single wire from the alternator, I think from a terminal marked W, (but the markings change depending on alternator), which runs to the multi-plug. I'd check the connection is correct on the alternator.   The oil pressure and water temp gauges have single wires from their senders which should go to one of the multi-plugs and then back to the instrument panel.  

I think, but I'm not sure, that the ground/negative for the tacho, oil water and voltage instruments are all from a terminal on the back of the tacho in a DV36. According to the wiring diagram it should be terminal 2, which should be the second from the right on the bottom of the 8 connector block on the block on the back of the tacho. This return goes, I think back to the alternator (B- usually the terminal, but depends on make).  Be worth checking these. 

I'm no electrical wizard, I've just spent a month trying to sort out a problem on our instrument panel wiring, so have got to know where things SHOULD go according to Bukh!
Good luck
Tony 

[petedg]

The problem has now been solved by attaching a wire from the Alternator B- to a ground connector on the engine and all 3 gauges are now working. The alternator now also seems to be working fine and delivering 14+ volts when measured at the battery bank. It seems the new alternator has an insulated return.
Thanks for all your comments.