Alright....so I'm kinda confused....not a rare occurance for me

If someone could do me the favour of giving the "Alternator 101" course on here I'd appreciate it

I'm just a complete dolt when it comes to shiat with wires that I don't have the fogiest

I'm trying to understand the relationship between Alternator's amperage in relation the motor and the car and the accessories

the questions simply come from my experience is buying alts to mod my cars

1) I went from the factory 130amp Alt in my Stang to a Chrome Powermaster 200amp alt....I did it simply for the bling....when I asked what the benefit of running a 200amp over the 130amp was....the response was "if you want to run a serious sound system it's perfect".....well, I did the sound system, but that's another story

2) I just purchased a replacement Alt for my Morgan (a 1990 3.9l rover V8) and it's only a 70amp......so I'm wondering why a factory car from 2000 comes with a 130amp and why a 1990 British car would only run 70amp

3) The Morgan has an electric fan and some idiot lights on the dash and it is an EFI motor and has a computer, but aside from that....no AC, no radio, no powersteering etc.....a far cry from the modern stangs list of electric trinkets....so does that make a difference in what the amperage should be? Although, this 70 Amp alt I ordered does say it's a replacement for a list of Land Rover's of that era which would have things like AC and a radio


so...I'm completely lost on the subject and would appreciate someone explaining this in a language I might understand

thanks

 

Bacially the more toys you have (a/c, power windows, power locks, stereo.....) the bigger Alt you will need. A/C, Defrost, and after market stereo's take alot of power specially if you decide to use them all at the same time. The motor really has nothing to do with how big of Alt you can install on your vehicle. Not sure if this is going to answer your question or not....

 

so the Alt is there for output so as not to drain the battery right?

and the output changes based on engine speed.....so if you're idling and running your heater full blast...all your lights are on...radio blasting, rear defrost, wipers going...etc then you'll probably drain the battery after a few hours cause the Alt isn't charging the system?

it's shedding light on why the Morgan is only a 70 versus the Stang's factory at 130....cause although it's got a 2 speed heater (2-speeds "OFF and Almost":laughhard), and an anologue quartz clock on the dash...as well as the electric fan and wishshield wipers....and obviously headlights (but not DRLs)....that's about it

hmm....I think I'm getting it

the early Ford Taurus had a 90 amp alt....but in the early 90s it went to a 120amp....I'm assuming that was because of daytime running lights?....makes sense as the lights will be a constant draw off the battery at idle

 

The ALT Charges are idle also The alt is designed to maintain the battery voltage that is used by items in the car. The Alt isn't designed to charge a dead battery therefore letting the ALT charge a battery after a boost isn't the best for a ALT.

 

Mach1Guy pretty much covered it.

 

I get it

probably another reason why the amperage of alts also seemed to go up in the 1990s because that's when all the factories started running single serpentine belts that power up everything with a pulley on the same belt which essentially slowed down the idle speed rotation of Alt pulley versus the multiple fan-belt design of the previous era?

so they would need a more powerful Alt simply to combat the lower output at idle....add in stuff like DRLs and it makes sense why I can run a 70amp

the alt on the Morgan only shares a belt with the water pump and crank

am I making sense?

 

The Belt doesn't really make any difference its more the size of the pulley that will change the speed. I am not 100% about this but doesn't alot of people that run under drive pullies have a problem with charging at idle?

Fuel Injection was problably the main reason for bigger Alts in the Late 80's- Early 90's. People want all this fancy crap on their cars so bigger Alt's are required. DRL's don't draw alot but ABS does when its activated....Fuel Pumps, Heated Seats....When A/C is on the Cooling fan runs. I know on my G/F's Caviler when you kick the ABS in when the Rear Defrost is on, Radio, Headlights the poor car almost has a brain fart LOL

 

I've heard underdrive pulleys can cause an issue

but my slant on the serp belts was looking at the Taurus going from 90 to 120....and both models were fuel injected....so I figured the serp belt might have had an effect on amp idle pulley speed so they just upped the amps because of it

I'm just trying to ease my mind.....even the Morgan factory couldn't tell me what amp came on the car....had to get the car up on a hoist to get a tag # and the tag only indicated 12 volts but no amps...and then apparently there's no line of this exact replacment alt

the folks I'm ordering from are serious gearheads in England that specialize in the Rover V8s so I'm pretty confident they're selling me the proper piece

just funny that when I say "70 amp"....most folks reply "that's pretty weak"

 

Lots of times the supplies we deal with at work have no idea what the AMPS are of a replacement ALT. They ask for the Tag off the ALT. 70 AMPS does seem like nothing but really there isn't alot that draws. Unless you plan to add a killer Stereo to it I imagine you will be more then fine. Stereo's create lots of problems with Stock Charging Systems

 

nope.....no stereo......although I love cruising with tunes, it seems almost criminal to install one in this car

been googling around and listings for 1990 Rover Alts are hard to find....but even the early-to-mid 90s ones were apparently only 80 amps so I should be good

appreciate the insight