Alternator problems .....continued

[nicknorman]

Good tip. So when I identify the right one, where the warning light goes out, that's one of the terminals for one side of my additional bulb.

 

Which is the other? I'm thinking battery positive, or B+ on the back of the alternator (i.e. it's output) such that the bulb would be connected to TWO of the alternator's rear terminals, making for a quick and easy job. No?

Yes!

[bizzard]

 

Thanks Biz. Sounds like the solution here. I'll get on the case on Monday and report back here. 6W -ish then!

There are two types of bulb and holder. The ordinary car type single pole using the holders body to complete the circuit so if installing into a metal switchboard might cause problems. Ideally a twin pole holder and bulb which will be isolated in a metal switchboard, these are available at auto electrical and commercial motor factors for use on GRP, wooden bodied things or like GRP bodied cars ect which don't have metal bodies or wings to complete the circuit.

[Loafer]

There are two types of bulb and holder. The ordinary car type single pole using the holders body to complete the circuit so if installing into a metal switchboard might cause problems. Ideally a twin pole holder and bulb which will be isolated in a metal switchboard, these are available at auto electrical and commercial motor factors for use on GRP, wooden bodied things or like GRP bodied cars ect which don't have metal bodies or wings to complete the circuit.

Noted.

 

If this works, I might just solder an additional bulb behind the instrument panel, to the spade terminals for the original. That should also continue to work if the original bulb blows. I can't see that being a fire risk, can you? It's just a bulb innit?

 

Does all this mean that, if the warning light ever blows, yer alternator won't excite?

[nicknorman]

Does all this mean that, if the warning light ever blows, yer alternator won't excite?

Yes. But with a caveat that I think not all alternators work in the way I described, though most do. Sometimes an alternator with a blown bulb will eventually excite (ie with enough revs) due to residual magnetism in the rotor.

[bizzard]

Noted.

 

If this works, I might just solder an additional bulb behind the instrument panel, to the spade terminals for the original. That should also continue to work if the original bulb blows. I can't see that being a fire risk, can you? It's just a bulb innit?

 

Does all this mean that, if the warning light ever blows, yer alternator won't excite?

Even a 6w bulb will get quite hot, secure it away from anything flammable like woodwork. Possibly not but an alternator that's been in use for sometime probably will excite with a lot of revs.

[smileypete]

Ive got a " test lamp " . Rigged up with a cabin light . Its the most well used piece of equipment on my boat , especially as it saw active service during my eberspacher episodes .

 

Is this what youre referring to ? One side is neg , one is pos .

 

Your saying pos to pos tho ?

 

Im sorry if i appear dumb , but my brains been fried by this issue & if connect up the wrong thing to wrong thing i may damage stuff .

 

If its ok & is suitable i ll use it

 

cheers

 

Sure, if you have a test lamp of a few watts, just disconnect the domestic alt warning lamp connection, then connect one end of the test lamp to it and the other end to domestic bat positive, eg the big B+ connection on the alt itself.

 

Only worth doing when no solar input and the alt warning lamp/buzzer is acting up.

 

cheers, Pete.

~smpt~

Edited January 3, 2015 by smileypete

[MtB]

Or, put the bulb on the back of the alternator permanently. That way you can see while you're in the engine room that it's extinguished instead of having to go back to the control panel.

 

And there are some alternators that self-excite, don't need the lamp at all apparently.

 

MtB

[Loafer]

Right, sorted. Both warning lamps were bean-sized 2W bulbs. Got replacements, same fitting, at 4W. Direct swap, now both alternators fire up at idle!

 

Brilliant chaps. Now that I know about greenies, I shall go back up this thread and issue a couple for this idea!

Often a resistor, or a second bulb, in parallel with the warning light (or else just changing the bulb to a more powerful one) will sort it.

Here's one greenie

I said a bigger bulb about 49 posts ago, or was it on the other thread of Chubby's.

I've now run out of greenies (just one per day?) but this'll get one

Sounds to me like all you need are bigger bulbs.

 

And this post will get a greenie around Wednesday!

The reason a bigger (higher wattage, higher current) bulb works is because the current flowing through the bulb is fed into the alternator rotor windings to magnetise the rotor a bit. This magnetised rotor, when spun at an adequate speed, induces lecccy into the stator windings. How fast the rotor has to spin depends on how much current is generating the magnetic field, ie the wattage of the bulb. Small bulb = weak magnetic field so the rotor needs to spin fast and vice versa. Typically (varies with alternator type) a set of diodes then rectifies the weak stator output and this is used to supplement the rotor / field current. As this current thus increases a bit the rotor magnetic field intensifies which increase the stator output current in a "vicious circle" which means the alternator jumps into life at that critical rpm. As the voltage at the filed diodes reaches 12v (or whatever) this means that not only is loads of field current now available (and it may then be restricted by the regulator) but als the voltage at the alternator end of the bulb is now 12v, same as at the other end, hence no voltage across the bulb and the light goes out.

Ed due to stator and rotor confusion!

 

And one here around Thursday!

 

Is this 'proper' use of greenies? That's 4, spent on an excellent solution to my query, plus one to MtB, spent during a thinly-disguised attempted robbery!!

Edited January 5, 2015 by Loafer

[chubby]

Can i ask , following on from this succesful outcome for Loafer , if when my alternator problems are ironed out & its working but needs revving to excite the alternator into life , would this remedy work for mine ?

I currently have to rev up from 900 - idle to around 1200 to get it going ( before it frustratingly turns itself off ) & a bigger bulb in voltmeter might cure this ?

I ll have to wait & see & once the alternator is functioning correctly i can look at doing this

cheers

[nicknorman]

Can i ask , following on from this succesful outcome for Loafer , if when my alternator problems are ironed out & its working but needs revving to excite the alternator into life , would this remedy work for mine ?

I currently have to rev up from 900 - idle to around 1200 to get it going ( before it frustratingly turns itself off ) & a bigger bulb in voltmeter might cure this ?

I ll have to wait & see & once the alternator is functioning correctly i can look at doing this

cheers

If the alternator light remains out when the engine returns to idle then yes, a bigger bulb should help to get it going. However if the warning light comes back on at idle (and I don't mean when the batteries are full) then the problem is to do with the pulley ratios and a bigger bulb won't help.

[OldGoat]

I get the distinct impression that your problems are due to your alternator is just not turning fast enough to generate any power until the engine gets to around 1200 rpm - as you report. SO increasing the lamp wattage may do 'not a lot'.

I had an engine with a very large 10" main pulley (well large for that engine type) and an alternator pulley of 3 1/2", giving a ratio of 2.8:1 and that needed spinning to 1200 rpm to get it to start.

 

Regardless of the above I am advised NOT to charge the batteries at engine idle speed but to increase it to 1100-1200 rpm OTHERWISE it may / will wreck the crankshaft keyway. It might take a long time - mine took 10 years and yet I always ran the engine at least 1100 rpm....

 

(I note that NickNorman managed to get in while I write this - but says much the same - 'cept the warning bit)

[chubby]

Thanks again

 

Im thinking the same thing about the alternator belt speeds . I thought that the rev up was to " excite " the alternator & then it could be returned to idle of around 900 -950 in order to charge whilst stationary . The bulb replacement question was for later , once the alternators behaving & to do away with the need to blip the throttle .

Very frustrating problem as i thought it was a straight swap of alternators but now its looking like it isn t . Im now " stuck " as to whether i ve got a wiring problem , a pulley ratio problem thats not spinning the alternator sufficiently at lower revs , or both !

what a carry on

Thanks again guys

[Semitrad]

I have looked at the alternator and refreshed my memory by looking at the correct rectifier and regulator. This is indeed a 9 diode machine and therefore self exciting. Perhaps the OP would be so good as to measure the voltage at the alternator output terminals when this occurs?

 

Does this mean that a different method is used to activate the warning light and buzzer?

[bottle]

Chubby

 

an alternator needs to be spinning at 3,000 rpm ++ so if you have a ratio of three to one, on the pulleys, then the engine needs to be spinning at 1,000 rpm ++

 

To work out your ratio, measure the biggest pulley diameter and the alternator pulley diameter, divide the smallest into the biggest, the answer is the ratio.

 

ie, largest pulley 6" diameter, alternator pulley 2", then 6/2 = 3, you have a three to one ratio.

 

This is only a 'rough' estimate as the groove depth of the pulleys will vary but good enough in this case.

 

 

edit: a word appeared in the wrong place after I posted.

Edited January 6, 2015 by bottle

[chubby]

Ok

 

i just ran my engine . Problems returned when i returned throttle to idle .

So

 

I re revved to 1200 to excite & progressively returned the throttle lever back & back until it returned - which it did , at idle .

 

When i left it at anything above idle - 100 rpm more ( idles at 900 ish ) the problems disappeared . I left it running at 1000 /1050 or so & it worked ok .

 

Since reading Tony Brooks comments about pulley ratios & having only one belt on my set up i ve tried to read up on other threads & elsewhere on tinternet to try & understand it & a bit of it has sunk in .

 

So , if i leave engine just above idle then it seems ok . But , i often run my boat at idle , when passing moored boats etc & often just like to mosey along the canal at this speed so the alternator " shutting down " at these speeds is not ideal .

 

If people think , going by what appears to be happening now , that its definately a belt / pulley issue , meaning at idle theres insufficient revs at the alternator pulley , then am i looking at having to replace the pulley on the alternator to enable it to spin sufficiently ?

 

Thanks

 

ETA Sorry bottle , crossed posts

Edited January 6, 2015 by chubby

[nicknorman]

Ok

i just ran my engine . Problems returned when i returned throttle to idle .

So

I re revved to 1200 to excite & progressively returned the throttle lever back & back until it returned - which it did , at idle .

When i left it at anything above idle - 100 rpm more ( idles at 900 ish ) the problems disappeared . I left it running at 1000 /1050 or so & it worked ok .

Since reading Tony Brooks comments about pulley ratios & having only one belt on my set up i ve tried to read up on other threads & elsewhere on tinternet to try & understand it & a bit of it has sunk in .

So , if i leave engine just above idle then it seems ok . But , i often run my boat at idle , when passing moored boats etc & often just like to mosey along the canal at this speed so the alternator " shutting down " at these speeds is not ideal .

If people think , going by what appears to be happening now , that its definately a belt / pulley issue , meaning at idle theres insufficient revs at the alternator pulley , then am i looking at having to replace the pulley on the alternator to enable it to spin sufficiently ?

Thanks

ETA Sorry bottle , crossed posts

Yes I think that is basically correct. Do you know/remember if the new alternator had exactly the same pulley size as the old one - or did you transfer the old pulley to the new alternator?

 

I think you are hitting a basic problem with your engine which IIRC has both alternators, and the water pump, driven from one belt. This inevitably means poor belt wrap and thus difficulty transferring power if the alternator has too small a pulley. This is why later engines had two belts, I think, one for each alternator.

[chubby]

Cheers Nick

 

It does feel like the problem is almost identified , as in its a mechanical issue not an electrical one .

Tony Brooks said that the one belt set up was bobbins & now im understanding why .

Would it be correct to simplify it as " the belt cant grip enough " .

 

Im uncertain about whether the pulley on the new alternator is the same as the old one . This might explain my annoyance at what LOOKED like a straight swap , but the pulley size might be different & so , yes it fitted straight in , all the connectors married up , but once the engines going , if the pulley size is even slightly different , then there will be a different performance . This prob hasn t occurred before & so when i swapped what i belived to be " like for like " , i may well not have .

 

So if one belt is not an ideal set up , i don t understand why it was used by Barrus Shire ( or is Barrus Shite ?) .

 

So , i need a solution . Is it too simplistic to say that it needs a different sized pulley which will be determined follwing some maths involving the engine pulley - ( 11 cm , i need to convert to old money once i ve been on google ) ?

 

Thanks again

 

ETA : i think im going to go back to the alternator chap & try to get my old alternator in order to establish if its a different sized pulley as i never had this prob before . Maybe if would fit on the new alternator .

If the one belt set up has been proven not ideal , so be it , but my electrical needs are small & the set up seems to be ok ( or was ) so i d ideally seek a solution that doesn t involve alot of alterations to a two belt set up ( unless its simple .... which i doubt )

cheers

Edited January 6, 2015 by chubby

[nicknorman]

Cheers Nick

 

It does feel like the problem is almost identified , as in its a mechanical issue not an electrical one .

Tony Brooks said that the one belt set up was bobbins & now im understanding why .

Would it be correct to simplify it as " the belt cant grip enough " .

 

Im uncertain about whether the pulley on the new alternator is the same as the old one . This might explain my annoyance at what LOOKED like a straight swap , but the pulley size might be different & so , yes it fitted straight in , all the connectors married up , but once the engines going , if the pulley size is even slightly different , then there will be a different performance . This prob hasn t occurred before & so when i swapped what i belived to be " like for like " , i may well not have .

 

So if one belt is not an ideal set up , i don t understand why it was used by Barrus Shire ( or is Barrus Shite ?) .

 

So , i need a solution . Is it too simplistic to say that it needs a different sized pulley which will be determined follwing some maths involving the engine pulley - ( 11 cm , i need to convert to old money once i ve been on google ) ?

 

Thanks again

I think it would be fair to say that the 1 belt setup was used because it was a simple and cheap adaptation when they went from 1 shared alternator, to 2. With 1 belt and 2 alternators, the belt doesn't wrap very far around each alternator pulley and that means it can't transfer much power. As alternators inevitably seem to get more powerful, and hence need more power to turn them, the lack of wrap becomes an issue.

 

Giving the engine 2 belts means changing to a double pulley on the crankshaft and moving the bracket for one of the alternators. Not that hard really, but they hoped they could get away without doing it I guess!

 

You may be able just to fit a smaller alternator pulley but if you overdo it, you will get belt slip. Maybe have a word with Barrus and ask what the original pulley diameter was.

 

For info on our Beta engine we have 3 belts, V belt for the engine alternator, polyvee belt for the domestic and another one for the travelpower alternator. That is how to do it properly!

Edited January 6, 2015 by nicknorman

[smileypete]

I'd try the test in post #81, if it excites sooner with a test lamp it may be the new alt just needs more current to get it excited.

 

A clamp meter would tell the output current at idle and various other speeds, but when the batts are nearly full they won't take much anyway.

 

cheers, Pete.

~smpt~

[chubby]

Ok

 

Slowly i think things are making sense :

 

Nick , your explanation was very good , especially to non techy like me . By " Belt wrap " you mean the belt physically has less contact with the pulley as a consequence of travelling around 4 pulleys instead of 2 ,and therefore the belt has less opportunity to transfer energy from belt to pulley and this results in slower pulley speed . Less revolutions means the alternator operates below its potential & may even lead to the alternator not functioning altogether .

 

Pete ,

Cheers again .

I shall carry out that test tomorrow :

Am i right to think that this test is adding another bulb / bigger bulb to the ignition lamp circuit ?

IF it works then this becomes like Loafers issue above . Change the bulb to one requiring more power / current / watts / amps etc & the alternator requires less revs to " excite " .

Does it also mean it will then require less revs to REMAIN operational

 

Or have i got it totally wrong and this is NOT what your test checks for

 

cheers again

Edited January 6, 2015 by chubby

[chubby]

Pete

 

Have i got this right .

 

1) engine on , rev 1200 , alternator excites , throttle back to idle & alternator fails , voltmeter warning lamp on , buzzer on .

 

2). with engine running , disconnect the " lamp " connection at back alternator .

 

3 connect bulb between battery +ive & lamp wire at alternator.

 

4) if alternator re excites then this means the red voltmeter lamp needs replacing & the alternator needs more current / power to remain functional .

 

Sorry for being such a problem child but if this is correct then i ll get it done tomorrow

cheers

[nicknorman]

Unfortunately whilst the bigger bulb might make the alternator start working at fewer rpm, it won't stop the light coming on again when the revs returns to idle. That is a pulley issue.

[smileypete]

Have i got this right .

 

1) engine on , rev 1200 , alternator excites , throttle back to idle & alternator fails , voltmeter warning lamp on , buzzer on .

 

2). with engine running , disconnect the " lamp " connection at back alternator .

 

3 connect bulb between [edited by Pete] domestic battery +ive & lamp wire at alternator.

 

4) if alternator re excites then this means the red voltmeter lamp needs replacing & the alternator needs more current / power to remain functional .

 

I'd stop the eng before fiddling with the alt, safer that way.

 

Try it out then IF a success consider the next steps.

 

Unfortunately whilst the bigger bulb might make the alternator start working at fewer rpm, it won't stop the light coming on again when the revs returns to idle. That is a pulley issue.

 

Not sure if it's due to the warning lamp being fed from engine batt instead of domestic batt. Maybe 10-20% likely but worth a 'sanity test'

 

cheers, Pete.

~smpt~

Edited January 6, 2015 by smileypete

[chubby]

Ok

 

Thanks again .

So im definately going to require a mechanical fix involving at least one pulley .

 

& i ll do that test tomorrow

 

Thank you so much again

[Loafer]

I said a bigger bulb about 49 posts ago, or was it on the other thread of Chubby's.

Just issued your promised greenie.

Ok

 

Thanks again .

So im definately going to require a mechanical fix involving at least one pulley .

 

& i ll do that test tomorrow

 

Thank you so much again

 

They're good, aren't they, these guys?

 

I have a firkin DEGREE in Lectric and I never knew how alternators were controlled. (Mind you, I was spanners, copper bars and man-sized insulators, in my electric field!)

Sounds to me like all you need are bigger bulbs.

 

Enjoy your post-humorous greenie. (Sorry, couldn't help myself typing that line again!)

Edited January 6, 2015 by Loafer