6 replies to this topic

[robminibcy]

Im looking to change my alternator to something a bit more powerful having just fitted a radio and new lights to my car. Ive not had problems yet (touch wood!) but want to be on the safe side and it has also been making a bit of a whine for a few months. Its a 79 car which I belive should have a 45 amp16/17 ARC type What ever the last bit means! After 1980 it seems that the standard alternator can be simply un bolted and a 70 amp one bolted on? Can i do this with mine? If not what will need to be changed or what alternator would be suitable.

[KernowCooper]

Your new radio wont draw that much unless you have a 500w sub in the boot, as for the lighs how many are we talking 2 - 4 ? are they 55w bulbs?

Lets do some maths

2x std headlights 55w each 110w
2x std rear lights 5w each 10w =120w which is 10amps to power them
If you add 2 more driving lamps of 55w = 110w is 9.16 amps

So now we have 19.16 amps power the std cars lighting circuit (exc dash/no plate)and 2 spotlights

If we fit 4 spotlights we add another 9.16 amps which would then be a total of 28.32 amps

If you sit down and work out all the dash lights and the number plate lights and the current drawn by the ignition system and any interior accessories like the blower motor and the heated rear window, you can see your 45a Alternator is really stretched.

But in the real world the likelyhood of running with the headlights on and 4 spots and the heated rear window with the blower motor running and the radio on and wipers is unlikely to happen for very long.

Now the testing bit, get your clamp amp meter out start the engine turn on all the things likely to be used lights, heater, wipers, blower and anything else you may use, and with someone in the car take the engine revs up to approx 3000rpm and observe if the battery is still being charged, and there is your answer.

There are indeed uprated Alternators on the market but they are not cheap, best to do the checks and see if you actually need one first.

ACR (Automatic Charge Relay) is the type of alternator which means it has a inbuilt charge regulator and the earlier alternators has a external regulator.

You can get a 70amp replacement to fit on the same mountings as your 45ampfrom mini spares and its not to expensive here http://www.minispare...|Back to search

Edited by KernowCooper, 16 February 2013 - 08:09 PM.

[robminibcy]

Cheers for that. The alternator in the link is the one ive been looking at and states as being suitable for 1980 on. will it still fit my my 1979 with out modification to wiring plug ect?

[KernowCooper]

If you have the ACR 17 45a now it should be a straight swap over I dont think the rear bracket is different. They state its a replacement upgrade on the site.

[robminibcy]

ok will see how it goes for a bit and then decide whether or not its going to want another present!

[A-Cell]

I would check the gauge of the cable from the alternator plug to the starter solenoid, it may not be capable of carrying 70amps. Later cars have 2 cables paralleled in a mica heatproof wrap. You may need to fit a bigger cable.

[KernowCooper]

Yep good point, you should see what gauge is there now.