Considering a change from 37 to 61 am due to added Underdash AC - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

 
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post #1 of 5 (permalink) Old Jul 11th, 18, 1:19 PM Thread Starter
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Considering a change from 37 to 61 am due to added Underdash AC

It appear from the instructions for the installation of my 1966 dealer accessories Custom Underdash AC that I can still use my 37 amp alternator. I have a manual 4 sp car with a radio and gauges for optional equipment. Nothing else.

Is a change to a 61 amp alternator a good ideal? A 61 Amp came with the factory AC' but I can't find anywhere that it talks about an amp change when adding the Custom AC. The AC probably won't be working at night, since I don't hardly ever drive in the dark. But I usually have my lights on during the day as way of making myself more visiable.

I was thinking about just swaping the parts from an old 61 amp along with a rebuilt kit to my current 37 amp alternator.


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post #2 of 5 (permalink) Old Jul 11th, 18, 1:32 PM
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Re: Considering a change from 37 to 61 am due to added Underdash AC

When I'm installing car amplifier's I'm adding to the load the alternator on the vehicle needs to keep up with and I hate to sell a customer or have him change the alternator if not needed so what I do is get everything installed and working and then turn it up to how loud the customer listens to it and then monitor the battery voltage. If the voltage stays steady at let's say 13.5V and does not slowly drop and drop, then there was enough reserve in the alternator to keep up with the addition of the amplifier BUT if I then see the battery voltage slowly going down from let's say 13.5V and then it slowly drops to 13.0V, and then slowly drops to 12.5V, and continues downward to let's say 10V, then the alternator is not keeping up.

Another thing with alternators is that a 37A model will have an output curve as well as a 61A will but at low idle speeds the 61 will probably keep up better if the total draw is let's say 35A and the motor is at a low RPM. A 35A rated alternator at idle might only put out 20A while a 61A at the same RPM might be able to output 35A.

Something I have not seen and I think is correct is GM used one main harness whether the car was equipped with a 37A or an optional 40's something amp or the even larger 60's something alternator to where if the car has a 37A originally, you can upgrade and not have to do wiring upgrades to those optional installed sizes BUT if you ever find yourself putting in a 90A, 100A, 150A, or larger, then wiring upgrades will probably need to be done as the original wiring was only sized to handle so much.

Jim

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post #3 of 5 (permalink) Old Jul 11th, 18, 4:23 PM
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Re: Considering a change from 37 to 61 am due to added Underdash AC

Forgot to add, when I'm doing this voltage test after adding the amplifier(s) I will also have the headlights on and the AC to load things up like it would be while driven.

Jim

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post #4 of 5 (permalink) Old Jul 11th, 18, 6:24 PM
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Re: Considering a change from 37 to 61 am due to added Underdash AC

I think this is the right one:

https://store.alternatorparts.com/10...nator-kit.aspx

David

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post #5 of 5 (permalink) Old Jul 12th, 18, 9:47 AM Thread Starter
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Re: Considering a change from 37 to 61 am due to added Underdash AC

Thanks guys, I am leaning towards buying an old origional 61 amp alternator and buying just the minimum new parts necessary to change a good 37 amp alternator so it puts out say 61 amps.

When I get the AC working I will have to check to see if the 37 amp keeps up using the battery test. Lights on, radio on, ac on high. Sounds like a good real life situation test.


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