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Warning light


Roxylass

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Delta to star. Done it before with an A127 and cut in speed reduces dramatically. Max current is of course reduced by the same factor. (root 3).

 

Just looked up and the A127 is indeed a Delta stator so can be converted.

 

Most alternators I have come across have been star, and on rare occasions have another pair of diodes connected to the star point.

 

I'm left wondering how compatible a 24V alternator is and whether a 12V regulator could be fitted for super low cut-in?

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Going to renew the battery lead to the alternator this weekend.

The battery says 140 ah on it what size mm thickness cable would I need

 

I don't see any reason why you can't connect a short wire to the Starter +ve lead. That is how mine is wired and in common for cars. It saves a lot of faffing about.

 

The alternator cable size is more dependent on charge current and length. I don't have a feel of what voltage drop is acceptable for an alternator. Thicker, of course, is better as is shorter.

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We here also have an open ex-ships GRP lifeboat which we use as a workboat. It has a Lister ST2 which also drives its alternator from the camshaft. It has the small standard pulley, the engine is mounted low down with a structural beam below the pulley so no room for a bigger one. The alternator is an old ACR with a 5w warning light bulb. A bit of a rev puts the light out and starts the charge, which is quite adequate for just charging an engine start battery. Originally the SR range of engines used dynamos before alternators came on the scene, You had to rev those right up to make the cut out cut in to start the charge if they had the small diameter pulley, but again they were adequate for just charging a start battery plus horn, lights and binge pump. Indeed a great many early pleasure cabin boats only had this simple set up too. I still have the charge rate voltage adjusting key for Lucas RB control boxes. A screw driver adjusted the earlier 2 coil control boxes. Not used the key for many moons though.

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Just looked up and the A127 is indeed a Delta stator so can be converted.

 

Most alternators I have come across have been star, and on rare occasions have another pair of diodes connected to the star point.

 

I'm left wondering how compatible a 24V alternator is and whether a 12V regulator could be fitted for super low cut-in?

Quite a few machines, A127 included, use the same winding in delta or star for 12 or 24V. A 24V stator in a 12V machine in effect.
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I don't see any reason why you can't connect a short wire to the Starter +ve lead. That is how mine is wired and in common for cars. It saves a lot of faffing about.

 

The alternator cable size is more dependent on charge current and length. I don't have a feel of what voltage drop is acceptable for an alternator. Thicker, of course, is better as is shorter.

 

If this is a boat such as Biz suggested without domestic batteries then that is fine BUT if it has a domestic bank then it is not.

 

Split charge diode systems need the charge to the diode first and the higher voltdrop suggests one may be in use.

 

Split charge relays and VSR systems need the alternator output to be connected to the bank that is the more discharged more often than the other so that means the domestic bank. If you wire such systems in the way you describe the system will work but you risk premature relay failure, especially if on of the more readily available relay makes is used.

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I don't see any reason why you can't connect a short wire to the Starter +ve lead. That is how mine is wired and in common for cars. It saves a lot of faffing about.

 

The alternator cable size is more dependent on charge current and length. I don't have a feel of what voltage drop is acceptable for an alternator. Thicker, of course, is better as is shorter.

Short wire to the starter positive lead other end to where

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I think he was talking about the main alternator output (B+) so the cable would run from the B+ terminal on the alternator to the main battery lead terminal on the starter SOLENOID but if you have split engine and domestic batteries please read and understand my last post.

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  • 3 years later...

Got another warning light lucas SBP 354 but it doesn’t give the amps on it 

its for a classic Land Rover certainly bigger than the one I have 

this should do away with the exciter switch 

or should I just stick with the exciter push button 

decisions decisions 

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1 hour ago, Roxylass said:

Got another warning light lucas SBP 354 but it doesn’t give the amps on it 

its for a classic Land Rover certainly bigger than the one I have 

this should do away with the exciter switch 

or should I just stick with the exciter push button 

decisions decisions 

If you remove the bulb it will have the wattage on it.  If you want to know the amps , divide the watts by the volts.  From memory it will be a 2 watt bulb so will draw 0.167 amps.

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16 minutes ago, Roxylass said:

Took the bulb out nothing on it couldn’t see anything on it at all 

even using the jewellers loupe here is a pic of it 

5AAEBF47-C136-450B-91AD-928E2CA5535E.jpeg

In that case, if you have a multimeter you could connect the light in series with the meter set to amps, then connect to your 12v battery. This will give you the current and from this you can work out the wattage.  Volts x Amps = Watts.

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That might even have an LED or grain of wheat (dolls house) bulb in it, neither will energise a typical alternator. You should be able to slide the bulb holder out of the body and bezel, if you can't then there is every chance it is still a low wattage bulb/LED.

 

You say you took the bulb out, was its base about the size of typical Christmas tree bulbs of the type used before LEDs became popular, either a screw fitting or  a push in one. (LES or LB base) if so it will be a maximum of 1.5 watts and again not high enough to energise many alternators. The "oil pressure" tag tells me that the wattage of the light source is not important for that duty s it may well be a very low wattage.

 

If you like the lamp you bought hen you can connect a resistor across the two terminal to increase the energisation current flowing. Sure someone will be along to give you the resistance and power rating.

 

 

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That "bulb" looks nothing like any I have seen before. The base cap is too fat and the glass envelope too small for the base. I think it may be an LED but the photo is too small to see a filament if it has one. If it is a filament bulb I would expect it to be about 1.5 watts.

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3 hours ago, Roxylass said:

Took the bulb out nothing on it couldn’t see anything on it at all 

even using the jewellers loupe here is a pic of it 

5AAEBF47-C136-450B-91AD-928E2CA5535E.jpeg

What you are picturing are a bulb holder and the box that is supplied in.  Ig you Google the part number it is supplied without a bulb.  The specified bulb for it at 12 volts seems to be called a 281, and these generally seem to be a 2 watt bulb.  So the current it takes will be about 0.17 amps, (or 170 milliamps,put another way).

The bulb in there should look like  this....

https://www.ebay.co.uk/itm/LUCAS-BA7S-281-MCC-CAR-DASH-PANEL-GAUGES-CLOCKS-SPEEDO-LIGHT-BULBS-LAMP-12V-2W-/153031068501?var=

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If that is genuine old new stock I doubt LED bulbs had been invented. Land Rover series 2 through to 3 was from 1959 to 1985. I don't think any of them used a red lens for the oil pressure light, either green or amber. Those were the days when red was always ignition charge light and almost always green for oil pressure, sometimes amber.

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1 hour ago, Roxylass said:

Here’s a couple of pics tried a few motor factors none of them 

seem to have a 5 watts biggest they have is a 2watt 

A1C02F7B-F440-4503-B325-8B36E08F75CA.jpeg

F6DCED83-1B32-4DBE-B64F-6C0F4BD97E7C.jpeg

A84086CD-1CDB-4F5D-933B-06172BF220B4.jpeg

45FDB258-C489-48C2-8661-6CB528B1EB3B.jpeg

They wouldn't put a 5 or 6w filament bulb into that small unit, the heat would probably melt it, 2.2w is the maximum I think. That unit is the usual standard size for those warning lights. The 2w bulb should be enough to excite the alternator as lowish revs. If you want to go to 5 or 6w bulb then the holder and lens will be twice the size, needing a bigger hole in the dashboard.

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I will certainly try this one at the weekend 

if it doesn’t come on when i turn the key 

dont wish to sound a defeatist 

think i will carry on with the exciter push button 

also check the thin wire bizz pointed out in one of the pics 

it does look rather tight 

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20 minutes ago, Roxylass said:

I will certainly try this one at the weekend 

if it doesn’t come on when i turn the key 

dont wish to sound a defeatist 

think i will carry on with the exciter push button 

also check the thin wire bizz pointed out in one of the pics 

it does look rather tight 

I've just realised you still have the small diameter pulley on the camshaft driving the alternator. In which case I think your going to need the 5w bulb and holder to excite the alternator into action at reasonable engine revs.

Edited by bizzard
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As you can see by the pics of the engine it has to be the smaller pulley 

the way the engine cradle sits on the engine mount these are original 

the boat was built by Viking marine then cheverton took them over 

number inside the boat 69 68 which denotes it was the sixty ninth built in 1968

all is original in it and I dont wish to alter anything think that would be a shame 

you couldn’t point me in the right direction where to purchase 5watt warning light 

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