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Wrong Alternator..?


Best Answer ACDodd , 08 August 2018 - 07:35 PM

Rev drop is normal on carburettor engines. Switching on electrical loads increases the load on the crankshaft. Running modern high output alternators makes this worse as they can put out high currents and low rpm. It's quite common for 998 mins to drop the rpm quite substantially when fitted with 70amp alternators when a load is applied at idle. Improvements can be made by optimising the ignition timing g at idle. Although the best solution is the adoption of an up idle solenoid that can be made up to suit. This effectively opens the throttle slighly when electrical loads are on. Modern engines using injection systems compensate in the same way by opening the idle speed control valve a little more when loads are applied to the engine.

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#1 MinesRed

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Posted 08 August 2018 - 07:10 PM

Hey guys.
Just been checking a few things today and I noticed that the Mini's revs drop dramatically,from approx 900rpm to approx 500rpm when I turn the lights on,even the sidelights.
They don't seem to change when the headlights and main beam are switched on.
The relay clicks but I have no means of testing the circuitry.
Could the alternator be too low a rating,I can't see any identification on it.
Oh yeah,1275 A+ motor.
Thanks folks.

#2 Bat

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Posted 08 August 2018 - 07:24 PM

Hi,

What's the battery voltage doing when this happens?

What makes you think the alternator is the wrong one?

Cheers  :proud:



#3 ACDodd

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Posted 08 August 2018 - 07:35 PM   Best Answer

Rev drop is normal on carburettor engines. Switching on electrical loads increases the load on the crankshaft. Running modern high output alternators makes this worse as they can put out high currents and low rpm. It's quite common for 998 mins to drop the rpm quite substantially when fitted with 70amp alternators when a load is applied at idle. Improvements can be made by optimising the ignition timing g at idle. Although the best solution is the adoption of an up idle solenoid that can be made up to suit. This effectively opens the throttle slighly when electrical loads are on. Modern engines using injection systems compensate in the same way by opening the idle speed control valve a little more when loads are applied to the engine.

Ac

Edited by ACDodd, 08 August 2018 - 07:36 PM.





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