Alternator problem?

[peteK]

One for the alternator experts.

Whilst running engine today I noticed that the ignition light was flickering on and at the same time the tachometer was dropping to zero,this wasnt the normal thing you get at low revs but at around 1200,when the engine was revved up it was ok.Didnt make any difference with the battery switch set to 1,2 or both.
The engine is 18hp Perkins perama with the standard alternator(A127)?

 

[oldvarnish]

I had a flashing alternator light this weekend. I waggled all the leads coming off the alternator, took them off and put them back on again, and the problem disappeared.

Worth a try.

 

[sailorman]

One for the alternator experts.

Whilst running engine today I noticed that the ignition light was flickering on and at the same time the tachometer was dropping to zero,this wasnt the normal thing you get at low revs but at around 1200,when the engine was revved up it was ok.Didnt make any difference with the battery switch set to 1,2 or both.
The engine is 18hp Perkins perama with the standard alternator(A127)?

loose connection or drive belt needs adjusting

 

[VicS]

+1 on the previous suggestions but if all connections are good and the belt correctly tensioned the next things to check are the brushes and the slip rings.

 

[peteK]

+1 on the previous suggestions but if all connections are good and the belt correctly tensioned the next things to check are the brushes and the slip rings.

Belt tension ok ,wire coming off the "W" terminal felt it was broken inside the insulation would that give these symptons.

 

[VicS]

Belt tension ok ,wire coming off the "W" terminal felt it was broken inside the insulation would that give these symptons.

Dodgy connection to the W terminal will certainly give you iffy tachometer readings as that is the "signal" connection for it.

Shouldn't cause the warning light behaviour you describe though.

 

[lw395]

could be brushes worn out or sticking in the holders?

 

[Burnham Bob]

if the alternator is a problem, get it serviced by an auto electrician, that's much cheaper than a new alternator from the engine manhfacturer which is probably one used on a japanese car painted in the engine manufacturer's colours!

 

[Stemar]

I think the first thing I'd do is clean all the contacts on all the wires coming off the alternator, also, remove the alternator and clean the mating sufaces to the engine.

Does the warning light only stay on when you first start and stay off when the revs drop after revving, or does it come on every time the revs drop?

If the former, it's nothing to worry about, if the latter and a good cleanup doesn't fix it, it's time to start saving your pennies for a refurbishment a la Burnham Bob.

 

[eagle160]

I had the same last week and was loose W connection but it was the battery low warning light switching on and off, not ignition.

 

[halcyon]

could be brushes worn out or sticking in the holders?

Best bet, typical of faults described by OP, but also check wiring for a loose connection as well.

Brian

 

[peteK]

Thanks for all the replies,
Alternator output is ok at 14.6 volts will check all connections next time on the boat,could possibly be dirty brushes but not noticed voltage drop when fault appears(have wired in voltmeter).

 

[peteK]

One for the alternator experts.

Whilst running engine today I noticed that the ignition light was flickering on and at the same time the tachometer was dropping to zero,this wasnt the normal thing you get at low revs but at around 1200,when the engine was revved up it was ok.Didnt make any difference with the battery switch set to 1,2 or both.
The engine is 18hp Perkins perama with the standard alternator(A127)?

Problem fixed it was dirty brushes but after cleaning broke one of the brushes reinstalling.