Alternator question

deadl0ck

Hi all,
Not sure if this is the right forum as the question is about a lawnmower engine, but the gardening forum is not really about engines so I though here would be the most appropriate....

Anyhow - my alternator seems to be shot on my Briggs and Stratton 11 HP engine.

I checked the alternator cable coming from the engine with a multimeter and the readings are all over the place - basically the readings are moving so quick I can't even read the multimeter. I disconnected the alternator wire from the rest of the system and took the reading from it directly.
Like I said - the reading is flickering and not constant at all.

Can anybody shed some light as to what this means - would it be the alternator or regulator ?

BTW : The engine is a B&S type 252707

thomas77

alternator cable?must be some lawnmower u have

Finnt

It's probably your regulator the coils on the Briggs engines produce ac current and you reg converts it that's why your readings would be all over th place esp your meter is set to vdc,
The reg is usually a little silver box with a black side on it it'll have 3 wires coming off it usually!
What make of mower is it?

deadl0ck

alternator cable?must be some lawnmower u have

Thanks for the constructive comments

It's probably your regulator the coils on the Briggs engines produce ac current and you reg converts it that's why your readings would be all over th place esp your meter is set to vdc,
The reg is usually a little silver box with a black side on it it'll have 3 wires coming off it usually!
What make of mower is it?

It's a Westwood S1100 mower (the 30" inch grass cutter one here) - it's about 20 years old but still going strong. The battery is dead but that's not such a big deal as it starts with the pull cord with no problems.
I'd just like to get a new battery and keep it charged up with the engine, as if I mow late in the evning I want the lights to work...

I'll have a look for the reg as you suggest
Thanks !

bbam

I've never checked on my mower but I'll presume it's the same as other charging equipment...
Surely you'll get a better indication at the battery??

The voltage at the poles will be more when the mower is running if the circuit is charging correctly?? 2-3V would be expected...

jimmyw

bbam wrote: »

I've never checked on my mower but I'll presume it's the same as other charging equipment...
Surely you'll get a better indication at the battery??

The voltage at the poles will be more when the mower is running if the circuit is charging correctly?? 2-3V would be expected...

I'd say your right, the nature of the alternator would not be stable, so the regulator sorts it out and sends it to the batt I suspect so check there.

BTW mowers and other petrol engined equipment are mentioned in the gardening forum OP

http://www.boards.ie/vbulletin/showthread.php?t=2055635176&page=41

See:)

Wheelnut

thomas77 wrote: »

alternator cable?must be some lawnmower u have

deadl0ck wrote: »

Thanks for the constructive comments

I'd be inclined to side with Thomas, the last thing you would have on a lawn mower is an alternater!

That lawn mower has either a dynostart in which the dynamo can reverse functions and act as a starter or a magneto which is the fly wheel assembly. I can't explain why, but I think you will find it difficult to get a normal voltage reading from either (especially if there is not good a battery in line). Just put in a new battery and I think you will find that it charges OK.

deadl0ck

It's got an alternator alright - here's the schematic for the engine :Clicky

BTW - it's an 11HP Briggs and Stratton Engine (It's a ride on mower - forgot to say that !)

Finnt

Wheelnut wrote: »

thomas77 wrote: »

alternator cable?must be some lawnmower u have

deadl0ck wrote: »

Thanks for the constructive comments

I'd be inclined to side with Thomas, the last thing you would have on a lawn mower is an alternater!

That lawn mower has either a dynostart in which the dynamo can reverse functions and act as a starter or a magneto which is the fly wheel assembly. I can't explain why, but I think you will find it difficult to get a normal voltage reading from either (especially if there is not good a battery in line). Just put in a new battery and I think you will find that it charges OK.

It is a alternator as in the magnetic field rotates around a stationary winding it's recommended to check out put from an alternator from the alternator first!!
As this eliminates faultly wiring and/or a faulty battery.
The only "dynostart" I've ever seen is on heinkel scooters. Havent seen one on anything modern.

Finnt

deadl0ck wrote: »

It's got an alternator alright - here's the schematic for the engine :Clicky

BTW - it's an 11HP Briggs and Stratton Engine (It's a ride on mower - forgot to say that !)

Did you get sorted?

ZENER

Have you checked the condition of F3 (3Amp) ? If the existing battery is faulty it might have blown.

To check the voltage from the alternator put the (+) terminal of your meter at connector 7. I presume the Diode there is a simple Half-Wave rectifier to give DC to the battery. From the diagram it looks like Alternator 1 supplies charge to the battery via F3 and the DIODE.

Ken

Wheelnut

Does your engine look anything like this?





I know that your's has a pull-cord and this one doesn't.

The photos show the engine of my late 90's ride-on mower, 11 HP and a 30" cut. The round thing beside the cylinder starts the engine and provides charging current, that's why I called it a dynostart. I can not find a regulator anywhere on the unit and any voltage test gives a huge range of readings. However it keeps the battery charged and each battery I have fitted (three in total) has lasted 4 to 5 years.

Finnt

Wheelnut wrote: »

Does your engine look anything like this?

I know that your's has a pull-cord and this one doesn't.

The photos show the engine of my late 90's ride-on mower, 11 HP and a 30" cut. The round thing beside the cylinder starts the engine and provides charging current, that's why I called it a dynostart. I can not find a regulator anywhere on the unit and any voltage test gives a huge range of readings. However it keeps the battery charged and each battery I have fitted (three in total) has lasted 4 to 5 years.

That's the starter your current to keep the battery charged comes from the red wire coming down from under the engine cowling.

deadl0ck

Yep - got it sorted - seems to be working

Yep - similar to the one in the picture but older looking !

The battery seems to b e completely shot - I thought it was holding some voltage, but I check it just now and absolutely nothing,,,

Wheelnut

Finnt wrote: »

That's the starter your current to keep the battery charged comes from the red wire coming down from under the engine cowling.

I had the starter off a few years back and my recollection was that it was permanently engaged, hence my conclusion that it was a dynostart. However I had another look at it today and Finnt is right. There is a sliding pinion to engage with the flywheel so it is purely a starter. I must have been having a senior moment.