Alternator slow to kick in

[petermills]

I'm sure that this is one that may been raised before, but here goes;
I have a Yanmar 2GM and my alternator shows a voltage reading of 14.3 volts when the engine is running on the fast side. When the engine is first started, the reading is only around 13 volts so I have to race the engine for a few seconds to get the voltage up to 14.3. Once this level has been reached, the charge rate remains constant even though the revs can been dropped to a tickover rate. Any ideas out there before I rush off and replace the alternator?????????

 

[VicS]

I'm sure that this is one that may been raised before, but here goes;
I have a Yanmar 2GM and my alternator shows a voltage reading of 14.3 volts when the engine is running on the fast side. When the engine is first started, the reading is only around 13 volts so I have to race the engine for a few seconds to get the voltage up to 14.3. Once this level has been reached, the charge rate remains constant even though the revs can been dropped to a tickover rate. Any ideas out there before I rush off and replace the alternator?????????

Don't rush off and replace the alternator. There's probably nothing wrong with it. If it is charging correctly once you have got it going there almost certainly is not.

Check the whole of the warning light circuit. Right from the connection at the keyswitch, through the bulb holder and the wiring from the bulb to the alternator. Check all the connections.

If all appears well try a slightly higher wattage bulb in the warning light.
The aim being to increase the initial excitation current

If all else fails check the sliprings and the brushes...
as last resort take the alternator to an automotive electrician to get it professionally checked. If there is something wrong it can be repaired at a fraction of the cost of a new alternator.

 

[Jcorstorphine]

Mine is the same.

I have the same problem on my Ford engine. In my case, the red lamp does not go out unless I blip the throttle once the engine has started. I have had the same advice as VicS gave and that is to make sure the wattage of the lamp is high enough.

 

[pappaecho]

I have twin Ford Mermaids, which I often run singly. I have a voltage monitor for the three battery banks. If I start a single engine the red ignition light will remain on unless I raise the revs to about 800 rpm. If I leave it at 800, the voltage will lowly rise from about 12.6 up to about 13.5 ( there is a diode splitter, so it will be dividing the charge between 3 different banks.Only if I raise the revs to 1600 do i get over 14 volts