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Amps Draw By Electrical Circuit


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#1 KernowCooper

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Posted 10 September 2015 - 10:10 PM

We get lots of question here asking do I need a bigger alternator?

How much current does my heater fan draw?

 

So I have put together a List below which is based on the Minis electrical system, all are rounded up to the next amp if more that 50% for ease of calculations

 

Side Lights Front and Rear 2amps

Dip Beam Headlights 9.16amps (55w Halogen Bulbs)

Main Beam / Flash Headlights 9.16amps (60w 10amps)

Indicators One Side 3.5amps

Hazard Lights 7amps

Stop Lights 3.5amps

Reverse Lights 2.5amps

Heated Rear Screen 10-20amps depending on the element

Dash Lights on Gauges and Indicator lights 2-3amps (Depending on auxillary gauges if fitted

Interiot light 0.4amps (5w Festoon) 0.8amps (10w Festoon)

Horn single 10amps

Heater Blower 6amps slow 10amps fast

Ignition Coil 12v 4amps

Cigarette Lighter 10-12amps

Wiper Motor Lucas 14w 1.5amps but stalled amps (frozen on screen/ seized wheel boxes,dry cable 4-6 times amps)

Number Plate Lamps 0.5amps

Spotlights (55w Bulbs) 4.5amps each

Normal Car Radio 3amps

Washer Pump 1.5amp but when rubber impeller swells 5amps on start

Parasitic Drain Immobliser/Alarm  <150-300mA depending on model of system

Starter Solenoid 10-12amps

Starter Motor 150amps when cranking 180+ amps on Initial crank

Central locking Solenoid (each) 3-4amps Non Standard

Power Windows 20-25amps Non Standard

1000w Amplifier 85amps Aftermarket for High End HiFi System

Cooling Fans, I have only tested the Kenlow range of fans and they vary with fan size from 180mm Fan at 4.5amps to the 400mm Fan at 15amps, The Kit for the Mini has a 255mm Fan at around 6amps

 

Obviously and Motor with tired windings the amperage will increase.

 

So a Standard Mini driven at night

 

Sidelights/Numberplate Lights  2.5amps

Headlights 10amps

Dash Lights 3amps max

Ignition 4amps =19.5amps

 

2 Extra Spotlights 10amps =29.5amps

 

So if we keep all the above active and then add the blower fan and radio which is approx 10amps were getting very close to the 17ACRs 45amp output, or if you have the earlier model 17 ACR rated at 36amps your in trouble

 

And Lastly I Recommend That Every Classic Car Should Have A Voltmeter Fitted To Keep A Eye On The Battery Voltage ( Auto Electricians Must Know When Driving lol), Rembering That At Low Engine Revs and Idle Your Battery Will Be Supplying Voltage Back Into The Electrical Circuit, Until The Alternator Can Overcome The Electrical Draw.

 

All the other items like Indicators are momentary and add to the total amps but for a short period

 

 



#2 Ethel

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Posted 10 September 2015 - 11:43 PM

Facet fuel pump (for carbs) 2amps

 

Injection fuel pump circa 10amps






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