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200 AMP Alternator for 1990 2.9L


Aoresteen

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I need a 200 amp alternator for my 1990 2.9L 2wd ac automatic. Any suggestions?

Also, how do I tell what the stock alternator is rated at? I see that the 1990 2.9L came with 60,75 or 80 amp alternators.
 


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Yes, you can buy 200-220amp alternators for 2.9l, not sure you could find one at wrecking yard

Alternator's output about 40% of rated amps at engine idle RPMs
Engine RPMs need to be close to 2,000 to get full alternator output

If you have power windows and AC then you will have the 75 or 80amp stock alternator

You can use a multi-meter with AMP setting to test alternator's output
 

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You can use a multi-meter with AMP setting to test alternator's output
You CAN do this, but you need to have the right meter, and be very careful.

A lot of meters only have a 10 or 15 amp fuse on the ammeter setting, so they won't give you a reading, they will just pop a fuse.
 

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just curious;
if ford thought an 80 amp alternator would power everything they put in the vehicle, what are you doing to it that requires 200 amps?
 

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just curious;
if ford thought an 80 amp alternator would power everything they put in the vehicle, what are you doing to it that requires 200 amps?
I was kind of wondering this too.
 

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Im thinking AMPS for stereo. Rolling studio.
 

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Actually an 80amp alternator only has about 35 amps at idle, 700rpms
Engine needs to be at about 1,600-1,800 rpms to get the full 80 amps

So all the vehicle needs is 30amps with all electrics on, fan on high and power windows rolling up or down
Head lights dimming at idle is not "normal", lol, no car maker specs in an alternator that can not power all STOCK electrics at idle.
Dimming head lights mean one of the three Fields in the alternator has failed, so you are not getting the full 40% of alternator capacity at idle, since you don't spend much time idling it is not a big concern............yet, but it does mean you should keep your eyes open for alternator sale :)


About the 200 amp alternator, one thing I forgot was that the 2.9l used V-belt not a serpentine belt.
When you change to a higher amp alternator it will require more horsepower to turn it.
Outside of the MPG drop there is also the matter of friction so V-belt doesn't slip, think 100hp engine and 6" wide tires, they don't slip easily, now think 250hp and same 6" tires.........you can "smoke 'em" easily, lol, thats friction, or lack of it
I am not familiar with the "wrap" on the 2.9l alternator, how much belt contact on the pulley, but if you start to get squealing, belt slip, you may need to paint the groove in pulley and use anti-slip treatment often
 
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Aoresteen

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Beter late than never. I need 200 amps plus as I will be powering 5 radios (HAM & various recievers) in the truck. Two will out put 100 watts RF power so they take 35 amps each minimum. The truck will be used ideling with a seperate 12V battery that needs to be charged. Yeh, they draw a lot of current. I will have a Honda generator that can be hooked up and power the radios when I am in the same area for a couple of days. I'm an ARES operator (W1AJO) that helps the local county EMA during emergencies.
 

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Beter late than never. I need 200 amps plus as I will be powering 5 radios (HAM & various recievers) in the truck. Two will out put 100 watts RF power so they take 35 amps each minimum. The truck will be used ideling with a seperate 12V battery that needs to be charged. Yeh, they draw a lot of current. I will have a Honda generator that can be hooked up and power the radios when I am in the same area for a couple of days. I'm an ARES operator (W1AJO) that helps the local county EMA during emergencies.
Look at adding a twist lock throttle cable, but make sure it can't effect gas pedal cable operation.

Alternator's AMP rating is at 5,500-6,000rpm, its RPM, not the engines RPM.
Pulley size is used to see what rpm alternator is spinning at
If crank pulley is 9" diameter and alternator pulley is 3" then its 3 to 1 ratio, if engine RPM is 800 the alternator is at 2,400rpm, 3 x 800
3:1 ratio is common on cars and trucks

At "idle"(engine at 800rpm) alternator outputs about 1/2 its rating, usually closer to 60% as its not strictly linear

Most vehicles spend their driving time with engine at 2,000+ rpm so alternator is at full AMP output most of the time

Measure your crank pulley size, and current alternator pulley size to get your ratio
You can then find best engine RPM for best output of alternator
Alternator doesn't produce more amps, above its rating, at higher RPMs, so no need to go above 5,500-6,000rpm
 
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Beter late than never. I need 200 amps plus as I will be powering 5 radios (HAM & various recievers) in the truck. Two will out put 100 watts RF power so they take 35 amps each minimum. The truck will be used ideling with a seperate 12V battery that needs to be charged. Yeh, they draw a lot of current. I will have a Honda generator that can be hooked up and power the radios when I am in the same area for a couple of days. I'm an ARES operator (W1AJO) that helps the local county EMA during emergencies.
Can you post a picture showing 5 radios in the truck?
 

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This may be an ignorant question, but why does 100 watts of RF require 35 amps? Seems like that's either incredible inefficiency or a miscalculation. 35 amps is around 500 watts with the engine running.
 

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A typical 100W radio transmitter does draw about 225-275 watts at full-carrier (100W RMS) output (no power amplifier circuit is 100% efficient), however this equates to roughly 18 amps at 14 volts, give/take a couple amps. Unless this is some sort of a continuous-carrier broadcasting operation, a transceiver also rarely spends more than 15-30% of it's time in transmit mode even with heavy use, so that lowers it's average current requirement to approx 6 amps.
For each 50-watt transceiver, you can add another 3 amps each (average current requirement). Each receiver? Maybe 1 amp, being generous. (most receivers draw under 0.5 amp)

IMO, a 200 amp alternator is well beyond what is needed here (upgrading to a 130A 3G unit should provide plenty enough juice to power 5 radio transceivers under typical use patterns, even at idle).
Only thing I can think of off hand that truly would require a 200A alternator would be to run a 1500+ watt AC inverter off the truck, though at that point a stand-alone generator would seem more practical unless space for it is at an extreme premium.

 

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Well a 200amp alternator would put out 120amps at idle, engine at 800 rpms
 

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Did the 3g upgrade to mine. Used the harness and alternator out of a 1995 Windstar. Easy as hell to do. With three massive fans (I'm NOT popping a head, damnit), stereo, inverter, etc. I still.havent found bottom.
 

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Can you post a picture showing 5 radios in the truck?
I want to see that too LOL. I tried a CB, GMRS, and a Ham Radio in my Bronco 2 and had a shelf installed in the place of the sun visors there's no room for all that unless you really start redecorating the interior LOL. I have I think an 80 amp and it does fine, the one that was on it when I got it had a bad field so it was barely hanging on. I believe it was a 65amp from the factory.
 

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