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MG MGB GT V8 Factory Originals Technical - Alternators


I find myself needing an alternator for my Rover 3.5

I currently have a Wilson Alternator #90-01-3106 12 Volt 63Amp 10SI
And since I need a new one I might was well go for one with more Amps. I am thinking something around 100amps 3 wire so I can still use the dash light and chrome.
With my conversation my current alternator is mounted on the drivers side (North America) and is just a little too big at 4.75 thick to tuck in tight towards the water pump.
I was wondering what everyone else is using


Bruce Mills

Hi Bruce:
Here's a pic of my alternator installation. It is quite small and only puts out 45 amps but has more output than the Lucas original. It fits very neatly in the space on the lower left side of the engine. It is a new takeoff from a Kubota tractor. Since I don't have lots of electrical "appliances" in my car it should do the job.

Just back from the bike trip in AK, BC and WA. Awesome trip! Covered about 3800 miles. Left the bike in Chilliwack.

take care

Phil O

Thanks Phil

I like the size of yours but I am running lots of electrical.
100/80 halogen headlights, 50W axillary lights, halogen brake lights, CD stacker, amplifier 8 speakers and CD player, electric fan etc, throw in the heater fan and wipers and turn signals on a cold wet fall night and I am using a lot of power. It appears the bigger the electrical requirements the bigger the unit.

Sounds like a great trip. Lots of great scenery

Bruce Mills


be careful with alternators that are capable of more amps than those used in the works V8. It is not a problem with the alternater itself, more power is allways a good solution, i think, but i ruined 3 water pumps with a 90 amp. Valeo alternator as they put much more load on the bearings as purposed by the designers of the pump.
When i changed back to a 55 amp version from Bosch, there were no problems with the charging but also no more problems with leaking water pumps!

My v8 is fitted with two 12 Volt 48 Amp Exide batteries, twin vents and all the other usual electrical equiptment.


Hi Bruce,

I use a 100 amp unit from a Range Rover, I needed a diode in line with the Brown/white wire that goes to the indicator lamp to clamp off leakage current. Works great.
M Mallaby

Thanks Guys

I have ordered a 100A 12SI. Should bolt right in where the 63A 10SI was. They have the same physical dimensions
Oh, and it is chrome too.

Bruce Mills

I use the next one up from what Phil is using, I think is used on most of the small japanese cars. Very near the same size and around 60-70A output. I have EFI, 100w halogens, big stereo amps and a optima battery. Last year the battery had a problem and it was charging 50A all the way from Cincinnati to Townsend, TN which made for one hot battery, but the alternator has done very well, no other problems.

Jim Blackwood

This thread was discussed between 11/06/2007 and 13/06/2007

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