selecting an alternator

[BammBamm]

I am looking at some alternators but some say "with A/C" What difference could having a/c make for the alternator on a 1982 spider? Isnt the alternator on a different vbelt.. I dont have a/c but I plan to add it.

[spider2081]

I think, for some years Spiders were delivered with a 55 amp alternator on cars without A/C and a 65 amp alternator for cars with A/C. I have read posts where some state there was no factory A/C installed on Spiders but then I am pretty sure I saw a Fiat Service Bulletin about changing the crankshaft pulley when installing a factory short block if the car has A/C. So I am sort of guessing.

[So Cal Mark]

the ac cars did have higher output alternators since there was more electrical demand. You really should consider on the higher output alternators that several of us offer. They cure a lot of low voltage issues throughout the car

[BammBamm]

Do I really need more than 65amps?

[chrisg]

Many argue no unless you are running massive lighting or a sound system. Is a binary (as in, doing nothing else), it's probably a bad idea to cure the typical 'vintage' Fiat type voltage issues. That said, once you've checked/cleaned & added good grounds as necessary & once you've checked for voltage drops across the various connections that often end up with corrosion & voltage drops, it's a logical next step. I'm running the popular 95amp units in twin cams these days, but I'm not at all opposed to a properly functioning 65 (or even 55 amp) unit..in fact, I have some good running 40 amp alternators from early twin cams. Years ago when I would still often run across low mileage wrecked 2L twin cams, ones with AC were the ones to snag the alternator from....but, since then the pickings of good used parts are gone, I'm older & less patient with trial-and-error & so I sort of follow what I said at the top of the paragraph. Maybe the answer is more a matter of your own economics, abilities & priorities than it is pure science?

As far as differences in the alternators themselves, I always found that all of the twin cam alternators interchanged. As I understand it, there are differences with the SOHC cars, but since I was trained early to avoid ones with AC anyway, I don't have much first hand experience other than rapidly dismantling a few over the years.

[spider2081]

My Question is. Why are you looking at some alternators? Do you have a problem with yours or is it just that you know you have an old alternator. Routine maintenance of the alternators is to remove clean replace brushes check bearings. Most 1982 Spiders came with a Bosch alternator and I think most were 65 amp rated. All the parts are easily sourced and if you are handy with tools it is an easy alternator to service. The brush block/voltage regulator assembly can be purchased for under $50 and replaced with out removing the alternator from the car in most cases. There are a number of youtube videos on how to check an alternator on the car. Also check or set the belt tension and replace it if you don't know its age.

[So Cal Mark]

you're missing some key issues with alternators. The rating, in this case 65a is maximum output and that is at a specific alternator rpm, usually around 6000 rpm. This speed is determined by pulley size. Your alternator won't put out 65a at idle or low speed. Check your alternator output at idle with all of your accessories turned on; lights, wipers, blower, turn signals and see what happens. You'll see a discharge, that's why your headlights dim while stopped and revving the engine makes them brighter.
The 95a alternators feature a smaller pulley, so low rpm output is much higher than your current oem alternator. With regard to voltage drops, every connection in your system creates a drop. .1v is considered acceptable at each connection but we commonly see much higher drops in these cars. It's common to see Spiders with voltages of 7-8 volts to the wipers and headlights. The higher output alternators will help overcome this.
If you're happy with your current alternator, by all means keep it, but you should know there is a much better alternative available

[DieselSpider]

My inclination is to fix the bad connections and wiring issues first and save fuel with the correct size alternator for the limited HP and torque of the engine. If my boat leaks too fast for the current bilge pump to keep up I'll fix the leaks instead of just pacifying things with a bigger bilge pump since after all is said the boat will still be leaking. Same thing with the alternator if you put a bigger one in to overcome electrical issues since after your done you really haven't fixed the real problem just masked it with a bigger alternator.

[BammBamm]

my alternator has stopped working and I can buy a remanufactured one for $50 on Rockauto. I have the 55 amp one and it didnt quite keep up with fully charging the battery. So I think the 65 amp will do for now. But when I upgrade my stereo and install an amp I may need to go 95 amp. In the mean time I will continue to clean contacts and replace connectors.. Thanks for the advice.

[spider2081]

My inclination is to fix the bad connections and wiring issues first

I completely agree. First fix the poor connections. No mater what you have for an alternator a poor connection is going to reduce the available voltage for the load. For example if you have a poor connection that has a 1/2 ohm of resistance. That is a resistance too small to be measured by most ohm meters. A load of 4 amps like some head light bulbs draw will cause a loss of 2 volts. It makes no difference what alternator is supply is supplying the voltage or how fast the alternator is turning. The 2 volts is lost across the bad connection. Some will say that a bigger alternator will supply a higher voltage. Yes they may but the poor connection will still take 2 volts from that higher starting point.
For me the fix is simple electrical maintenance. Electrical connections must be kept tight, corrosion free and clean.