Thursday, September 8, 2011

Alternating Currents - Alternator Woes

2011 09 08
Ferragudo, Portugal (across the river from Portimao)

View At  Anchorage in Ferragudo on the River Arcade
(across from Portimao)
We made about 300 meters distance made good yesterday.  Our dinghy arrived on time (if 12 days on a 10 day promise can be considered on time.  Our broker very strongly suggests that he delivered on his promise "ahead of schedule - Portuguese time". Clearly he had no intention of delivering the dinghy in 10 days or even 12 had it not been for the eruption of Mount Curmudgeon.  It only took 7 days to make heaven and earth - six if you don't count the day off at the end.  Proof that God was not Portuguese.

Dinghy on board we departed the marina in Portimao intending on dropping hook in the convenient nearby anchorage in the River Arcade to prep for departure today on our way to Sevilla, Espanha.  Immediately we noticed the alternator was not alternating.  NO electrons were being generated.  No power created to feed our voracious batteries.

No one expects their alternator to fail.  Like the Spanish Inquisition surprise is trouble's first weapon.  That and a near fanatical devotion to the pope I suppose but that is less relevant here.(m. python rules)

Along with all the other important devices on our boats the alternator is much abused, much neglected and generally ignored.  Until of course it up and quits.

Without an alternator you will be forced to sail, not motor, and to hand steer.  Your battery bank cannot support you and your insatiable appetite for electrical energy for more than a day or two usually much much less.

Your fridge is drawing 3 amps average and without that your beer will get warm.  When you run it the diesel eats from 2 to 5 amps powering the fuel pump and the instrument panel and such.  Your autopilot is good for at least 5 amps and a lot more if conditions are rough.

So there you are: sailing not motoring, hand steering with only warm beer.  Sounds like a Corsican slave galley.  No thank you.  You gotta get that thing working.

Here are some things you can try that should breath some life back into the poor dear thing.  Unless you have totally fried the alternator, a very unlikely event, one of these procedures should get you on your way.

The Big Three 

THe natural response of all of us faced with the overwhelming depression of a failed alternator is to throw open the engine compartment and stare blankly at the engine.  Just what compels us to join in this act of bovine placidity I cannot answer. It never works and no broken part has ever started to work after a good hard look at it has been effected.  Not on my boat anyway.  But I keep trying.

In seventy five percent of the cases of alternator failure one of these three procedures will get you on your way:

1. Take off all the connections from the alternator to the battery.  Everything.  Every peid of wire even the ground wire.  Clean the ends of the wire thoroughly and then clean the contact points on the alternator to which these wires connect.

2. If your alternator is externally regulated , and I assume for this blog that your alternator is externally regulated, remove the harness connecting the alternator to the regulator and clean all the contacts - including any stray wires that do not look important.  There will be at least one sense wire from the regulator to a switched negative post.  Check and clean both connections on this sense wire.

3. Check your fanbelt to make sure you have good tension and then check the fanbelt surface where it contacts the pulleys to make sure the belt has not glazed over.  Glazing can make the belt slippery. When it comes to fan belts slippery is useless.

With only a small amount of work and just a bit of luck you should now be on your way.


First Try THis - but only if you have an externally regulated P type alternator.

1. With the engine off place a steel screwdriver blade or steel wrench near the nut on the pulley of the alternator.  There should be no evidence of magnetism, ie. there should be no pull on the wrench or screwdriver trying to pull it towards the pulley nut.

2. Start the diesel.  Wait about five minutes.  Now CAREFULLY place the screwdriver blade or wrench near the pulley nut on the alternator.  YOu should find a strong magnetic force pulling the blade or wrench towards the pulley nut.

THis is a bit dangerous cause the diesel is on and you are close to moving parts that can maul you quite seriously and even kill you.  For the sake of my lawyer I must now tell you not to do what I have just suggested.  It is dangerous and no one, even a professional mechanic working in a protected environment wearing half inch kevlar protective clothing would never try to do what I have just suggested.  It was a joke and I did not mean it.

If you are squeamish about losing an arm or watching your entire alimentary tract wind itself up on the crankshaft of your diesel remember that you do not have to start the diesel.  You can be safe.

Just turn the key to "run", wait five minutes and then test with the wrench or screwdriver blade.  However - that annoying oil pressure beeper will be sounding non stop and if you have an oil pressure cutout switch on the diesel you will have to short circuit it.

Entirely up to you what you do but if your arm gets ripped off don't blame me.  I'm broke anyway. (You wait the five minutes because most external regulators have a delay programmed into them and they do not start up right away to give your diesel a chance to get up to speed before they load the engine with the alternator.

3. If there is a strong magnetic field at the pulley nut on the alternator but the alternator is not producing any current then I am sorry.  You are screwed.  You are going to have to take the alternator off the boat and have it rebuilt. On the bright side you will not have to waste any more time working on the darn thing and you can devote the rest of your afternoon to drinking the beer before it gets too warm.


1. Turn the engine off and remove the key.  Disconnect the wires running from the regulator to the the alternator.  Usually this means pulling off a harness or plug. The wiring from the alternator to the regulator will likely have wires in the following colours: black, red, white, brown, blue.  We are only concerned with the blue wire and red wire.  THe blue wire may not be blue.  Blue is usually the colour used for the "field" wire; it carries current from the regulator to the rotor on your alternator.  If you do not have a blue wire read the manual for the regulator and find out what colour France or England or Germany use for their field wires.

2. Using a small piece of wire connect the blue (field) wire to the red wire.

3. Check for magnetism at the pulley nut on the alternator.

If there is magnetism on the pulley nut it looks like your alternator is ok, at least the rotor and brushes and the regulator harness is ok, ie. there are no shorts in the wiring harness.  This means that probably your regulator is the problem.  Hook up your spare regulator and you should be on your way.

If you do not have a spare regulator then shame on you.  You deserve to be stressed out because you are woefully unprepared.  All is not lost however and you can make a regulator out of parts normally found on most boats.  Read Nigel Calder's book on Electrical and Mechanical Maintenance for directions.

Simply wire together a n series a bunch of light fixtures or whatever you have that use power  until you have a circuit with enough "power consumers" to use  5 amps of current.  (a ten watt lightbulb uses about 1 amp so five of these wired in series would be good).  Then wire one end of the circuit you have made to the positive post and the other end to the blue (field) wire.  You might want to wire in a switch as well to turn the string of lights on and off.  Start the diesel and when it is running smoothly go below and turn on the string of lights.  This will run enough current through the rotor of the alternator to produce about 13 volts to 13.5 volts, enough to charge at an elementary level.  Use to your voltmeter and verify that the alternator is putting out no more than 13.8 to 14 volts.

4. If there is no magnetism at the pulley nut get out your voltmeter and check for voltage on the blue (field) wire.

If there is no voltage then likely the problem is a short in the wiring harness.  You can track that down with your voltmeter and clean or cut out the bad wiring or connection and rewire.

If there is voltage at the blue (field) wire and there is magnetism at the pulley nut once again you are screwed and are going to take that alternator into the shop for a rebuild.

No matter what result you obtain when you are done you have earned the right to a beer.  Hope it's cold.

Thoughts on Alternator Maintenance and Preparedness

1. Carry a spare regulator.  They are inexpensive.

2. If you are cruising carry a spare alternator.

3. Clean your alternator regularly.  Use your wife's vaccuum cleaner to suck out bits of crud from the alternator (tell her it is just dust).

4. Check belt tension on the fanbelt often, like every time you start the diesel.

5. Every two years remove your alternator and take it to a good starter shop for a rebuild.  They will clean and lube it, change out the bearings, replace the brushes and check all the other parts, like the diodes. Cost is usually about $150 in Canada.  Use your spare alternator while the rebuild is being done.

While you are at it you might take in the starting motor too.  It needs attention as much as the alternator.  While you are in there you might as well change the air filter and pull the bilge pump to clean the vanes and the pump switch, tighten the stuffing box, check the tranny fluid, remove the heat exchanger and flush the seaweed and mud out of it, remove and scope the exhaust, lube the through hulls and verify smooth handle action and check all the other electrical connections.

I mean you are in there anyway.

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