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MG MGA - Correct Alternator

I am in the process of putting an alternator on my 1800 engine. I bought the supposedly correct item for the B-series engine from my local supplier and have had no problem fitting it on the car. All the rewiring is done in line with Barney Gaylord's instructions, but I have yet to fire the engine as I still have the radiator out while attending to other small jobs.

However, looking at the alternator the small fan that sits behind the pulley appears to be optimised for anti clockwise rotation (when viewed from the front) rather than clockwise. The 'folded spine' of each fan blade faces the airflow instead of the 'open blade' Is this a problem? Is it in fact a cooling fan? Can an alternator spin in either direction?

Regards

Steve
Steve Gyles

Steve,

Looking at a photo of a B engine, the alternator fan blades should have the "bent back" piece on the right (when looking from the front).

I'm subject to corection on this but I think an alternator will work equally well in either direction. I think the stator coils are wired in star formation so the diodes will look after polarity.

I've never checked this but I was told that Honda engines run anti-clockwise.

Malcolm
malcolm asquith

Hi Steve, I far as I know your alternator can only run clockwise as viewed from the front, the fan must be OK if its a standard Lucas type, I'm assuming you are using a LRA100. As mentioned, Honda engines run backward's and some Misubishi ( clever, these Japanese!). Have you used the longer bracket for the rearward mount or spaced it? As you may remember, I'm running a Racemettle Dynalite, which looks like a dynamo but has alternator type internals. I've retained a control box, which has been gutted and two heavy duty 50/60 amp mega fuses used to connect the power wires. You're probably better off connecting a +'ve wire from the alternator staight to the solenoid and then take your live feed from there, I put in an extra wire to do this so that I didn't have to butcher the loom. My yellow from the control box connection's doesn't connect to anything at the alternator end. This is alot easier to see in the flesh than trying to explain ( a picture paint's a thousand word etc etc )


Lectrical Terry
Terry Drinkwater

Thanks for your very helpful comments and reassurance Terry. Mine is made by Startmaster (who I have never heard of before). The box says its type MA0460, suitable for MGBGT 1975 to 80. My engine is from a rubber bumper B.

This type of B-series engine has the 4 tapped holes (rear 2 for dynamo, front 2 for alternato). I manufactured quite a neat plate that uses all 4 holes. I did not fancy the spacer tube and long bolt option.

I totally understand your wiring modification. One of the conversion write-ups says to do precisely what you have done - to cater for the heavy loads through the wires when the battery is low on charge.

Nudged Steve
Steve Gyles

The fan is a "centrifugal" one - the airflow comes from the back of the alternator, through the works, and is flung (izzat a word?) out radially from the front. So the blades are formed to block flow coming from the front of the car, keeping the two flows from interfering.
FRM
FR Millmore

FRM

Very many thanks. Makes total sense now.

Steve
Steve Gyles

All working ok at first time of asking. Barney Gaylord's instructions and the Moss instructions were spot on and made the job very easy. I also put the optional heavy duty cable between the alternator and the starter switch (mentioned both by Barney and Terry above).

Very many thanks to you all.

Steve
Steve Gyles

Steve; Do you have an equally heavy ground strap? Glad things went so well for u. Bill.
w.g cook

Hi Steve

A bracket for your alternator was fitted to all 'A' and 'B' series blocks fitted with alternators, as far as I know it is the same bracket. It was probably fitted to a MGB aswell, mine came from a 1622cc Sherpa Van block. Hope it all works.


Terry
Terry Drinkwater

Terry

In due course i may source the correct bracket. Half the fun is making do and fabricating your own bits and pieces (ask Glen's friend). As you may well know, the holes for the alternator bracket are spaced differently to the generator bracket, so it is not just a simple case of moving the generator bracket forward into a new location.


Bill

The A's wiring has numerous earths all over the place in addition to the very heavy lead from the battery to the chassis. I am not quite sure what you are suggesting.

Steve
Steve Gyles

This thread was discussed between 04/07/2005 and 08/07/2005

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