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Stock Alternator delayed startup?

cawinter

Member III
This is one area that, to this day, evades me... :)

I noticed this season (may have happened earlier) that the factory alternator upon engine start in fast idle does not deliver current to the batteries. Link10 shows the batteries at resting voltage with current coming OUT (fuel pump). This condition persists for at least a minute in fast idle and doesn't seem to change unless...:

When I rev up to perhaps 2500RPM I suddenly get the alternator to kick in. Voltage and current are good and in the right direction.

I know the Balmar controller has a time delay, but that can't be the case here. Batteries are reasonably well charged and the belt is tensioned.

Any ideas before I get the wrench out?

Thanks.
 

Guy Stevens

Moderator
Moderator
Oil Pressure switch or maybe it does work that way

This is pretty Normal, and generally a good thing. The alterantor field can be wired through an oil pressure switch, or a heat sensor to make sure that the oil or the temp are up before switching on a load.

Also some of the "Stock" alternators with controllers built into them have a start up delay on them now too. They may not have been the one that came with the engine, but a replacement. Look up the alternator by manufacture here on the web and find out if it may be that way on purpose.
 

cawinter

Member III
Motorola features?

Guy,

"The alterantor field can be wired through an oil pressure switch, or a heat sensor to make sure that the oil or the temp are up before switching on a load." I am sure it is not. Would make sense but not here. I know the Balmar goes all out with configurable start-up sequences. Nice.

This would have to be a timing thing but I waited and waited... :confused: and only the RPMs woke it up.

My next big trip is in a few weeks. I may just get the wrenches out and have it checked just to be sure.

Thanks!
 

Captron

Member III
Alternator Delay

Some alternators need to have the field excited before they start putting out current. A quick rev usually does it. The system is supposed to have some resistance in the field wire. This is usually in the form of an 'idiot' light that comes on when the key is turned and goes out when the alternator starts charging. That resistance energizes the field.

Get a copy of Don Casey's book "Sailboat Electrics Simplified" it has good explanations of that. It's also a handy reference for lots of sailboat related electrical system recommendations and fault testing methods.

:egrin:
 

ted_reshetiloff

Contributing Partner
It sounds like you need a pretty high rpm to excite the field. Has it always been this high? 1500 is normally about all it takes to excite a stock alternator. I would do as Ron has suggested and get the book and do some testing on the alternator. Internal or external reg? Clean terminals and connections everywhere? Maybe resistance build up is causing this high of a threshhold. May also be cheap to pull the alt. have it bench tested?
 

cawinter

Member III
Bench test

Yes, I think I'll just pull it out. Internal regulator, and I believe it is the original Motorola (?) 50 or so amp model. I had it tested a few years ago, and, as far as I remember, all it always took was a quick rev-up to get it to start but not over 2000RPM.

As a side note, and not throw fire into the Link10/20 or whatever discussion, the only way I saw this was because of my Link10 setup with the shunt measuring total current in/out of the battery. I could have looked at the factory panel meter forever...;)

Thanks for your thoughts!
 

Tom Metzger

Sustaining Partner
As a side note, and not throw fire into the Link10/20 or whatever discussion, the only way I saw this was because of my Link10 setup with the shunt measuring total current in/out of the battery. I could have looked at the factory panel meter forever...;)

Yes, but you would have been happy until you looked at a voltmeter. :nerd:

I am a big fan of Link 10s, have had mine for about 11 years, but would not recommend one to a day sailor. Too pricey. Better to take the switch out of the panel voltmeter circuit so you can always see what the voltage is on the connected bank AND the current.

Keep in mind that thirty years ago we sailed very happily with only a six channel crystal radio for electronics, and we usually got home safely. :soapbox:
 

cawinter

Member III
Ok. Agree on the voltmeter. That would have told me there was a problem with the voltage on the banks... No voltage above resting...ergo no current into the batteries!

As far as the total current goes though, you would have to set up a shunt or something at the battery (and not the panel) to see the electrons coming from the alternator. Stock setup does not allow that, and we all disabled our measly engine panel indicators based on your schematics, Tom. :)

Anyway, having just spent quite a bit on my Micron66 (not a new thread), I thought the Link was a relatively good investment, which also addresses my paranoia issue...

Other than that, a great year so far. I got my RADAR working finally (C80) and all other disasters from Ernesto and Co. are cured. Oh...I totally agree on the 'wooden boats and iron men' approach of the minimalist...just tough when other significant people have diverging opinions. ;)
 

Captron

Member III
Oh...I totally agree on the 'wooden boats and iron men' approach of the minimalist...just tough when other significant people have diverging opinions. ;)


Especially when it comes to heads, stoves, rugs, storage, not sailing when the wind blows. etc. :cool:
 
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