Generator to alternator conversion

[Deanj]

Check the post "Generator Upgrade". Everything is there on converting to an alternator.

Dean

[lake bird]

alternator selection ?

Just trying to select the proper amperage alternator to do the
conversion...have reviewed all the postings, ready to go after purchasing all the components...
The Tuff Stuff7068 is considered, but it's a one wire, would like to retain the use of the gen lite for alt failure or belt loss indication...
The 7127K is 140 amp 3 wire, plan on doing the Concour dual electric fan set up also...larger alt would be best.

Steve M/Rockwall,Tx

[simplyconnected]

...The Tuff Stuff7068 is considered, but it's a one wire, would like to retain the use of the gen lite for alt failure or belt loss indication...

The only way a one-wire know to turn on is when rpms are high. That means at low idle speeds the new alt turns OFF.

3-wire alts use the GEN light signal to actually turn on the voltage regulator so the alt will produce power at low idle. This is convenient because the GEN light is powered by the key switch. Putting it all together, the key turns on the alt.

You're right about the GEN light. It will function exactly as you would expect when used with a 3-wire alt.

How many amps do you need? Look at modern cars with electric fans. Find out their amperage. I use a 130-amp with my electric fan. I can crawl/cruise in a parade all day without draining the battery or overheating. - Dave

[Deanj]

How many amps do you need? Look at modern cars with electric fans. Find out their amperage. I use a 130-amp with my electric fan. I can crawl/cruise in a parade all day without draining the battery or overheating. - Dave

Dave, many posts, I believe, "suggest" a 65 amp alternator maximum for the car's thinner gauge wiring. I read the generator cars because of their 30 and 35 amp ratings could or should only support a 65 amp alternator. I know a 130 amp alternator will drag a lot more on the engine begging for more grip on the pulley, also.

Dean

[simplyconnected]

The size of your generator/alternator solely depends on the load (and nothing else). The size of your wires should be matched to your alternator, not the other way around.

My Mustang GT came with a 75-amp alternator and a mechanical fan. The cooling system would overheat in the Woodward Dream Cruise because the event is at crawl speeds for many miles.

Ok, I added an electric fan. The fan dutifully kept the engine cool but that 75-amp alt couldn't produce enough power to match the fan's 25-amp thirst so the battery drained as I drove. I could actually see the system go down to ten volts, which is dangerously low for an EFI engine.

The solution was to mount an alternator that produced enough power to sustain the fan at idle speeds, which is exactly what modern cars have.

This isn't a contest to find the largest alternator for my engine. I don't need 130-amps. I don't need 75-amps. I need 25-amps at idle speed which is what the 130-amp alt produces. Now that I have a source of power large enough to meet the demand, alternator wiring must be sufficient to safely carry the current. Furthermore, since alternators are solid state devices, an overcurrent fuse must be installed to protect the wiring in case one of the diodes or SCRs suddenly shorts to ground inside the alt.

A blown fuse will divorce a faulty alternator from the system.
Then, it prevents the alt wiring from burning and the battery from draining. This allows the engine to start again and the battery should have enough in reserve to get you home (or close to it).

This is a system, that needs to be scrutinized in its entirety. Every component must be sized to meet or exceed the demand. This was true when your 30-amp generator was installed with #10 wire.
A 35-amp generator required 1/2-HP on the belt (and only at high RPMs). A 130-amp alt requires 2-hp on the belt but only for a short time.

Every car's electrical demand was very low back in the day but times have changed dramatically. In addition to electric EFI fuel pumps and electric fans, I see electric coolant pumps coming, all in the name of 'saving gas' (or HP). Mechanical water pumps are inefficient because they are deficient at idle speeds but are excessive at high RPMs. A popular 'trick' racers use is to run their mechanical water pump from a small heater motor. - Dave

[Deanj]

OK, I know the wire to battery size is determined by the alternator size. Probably an 8 gauge for a 65 and a 4 gauge for a 130, but how would you adjust the rest of the wiring system reasonably? Beside cost, why do Mac's and Larry only offer 65 amp units?

Dean

[simplyconnected]

Don't adjust any wire size other than the one connected between the new alternator and your starter solenoid (with a fuse in between). The alternator's job is to feed the battery and the accessories you have running.

I think you can get away using a #6 wire for the alternator because the run is so short, it's in free air and the duty cycle (amps over time) is very low. Devices that draw a lot never run for long.

In our Michigan winters, my daily driver's electric fan may not turn on for MONTHS. As long as the car is moving, cold air keeps coolant in the radiator cold. That was also true in my 351W Mustang. I drove it to Dearborn for 16 years.

I cannot speak for the vendors except to say, they're in business to sell replacement parts for classic cars. Prices for generators with regulators is even higher than a modern alternator with an internal regulator. I'm not a purist but many of our members are. - Dave

[lake bird]

alternator choice

Guys looking at a tuff stuff 7127 D is a one wire or OE wiring

has the conn R &F ...comments about using with chevy waring lite. would this work ,which term to the gen lite " I" lead.

Steve M.

[simplyconnected]

You're wise to stick with a 3-wire because those are standard replacement alt's. As such, every parts store has them at reasonable prices.
Call me 'cheap' but I don't spend $100 for any alt. Here's a new 130-amp on eBay for $67 (no core charge and free s/h) and it comes from WV with a 1-yr warranty. CLICK HERE

If you need pigtail connectors, they are also available on eBay and at your local auto parts store. These alternators accept standard 'V' groove pulleys that are also available on eBay.

Sorry, but I have no love for overpriced alt's. As far as 'brand', I doubt those electrons know if they came from a Ford or VW alternator. Find a 12-volt neg ground alt that is easy to mount. Wiring is always secondary.

I don't understand the attraction of a one-wire alt. An OEM alternator (3-wire) has a battery wire, a GEN light (or key switch) wire and a ground. The one-wire has a ground, so it is really a 'two-wire'. It has no signal from the key switch to turn on/off.

LakeBird, GM alternators use three wires and a ground:

• Batt - connects to the battery
• 1 - connects through the idiot light to the key switch.
• 2 - is a 'sense' wire, used to sense the key is on and also used to sense any voltage drop in the system.
• GND - is the case ground.

Ford combines GM's #1 & #2, from the key switch, through a GEN light (or not) and finally to the alt. If this wire is broken the alt won't produce.

GM's setup is the same. If #2 is disconnected from power, the alt won't produce power. Some folks connect #2 to the alt's BATT post. - Dave

[lake bird]

alternator choice

Sounds great, type of input I was looking for....
CRAP was a newer variable 2 piece bracket for the older 352 FE
distance between 180 deg mount holes can very with it..the fixed one piece is 6 7/8 inches...so...the two piece for the older 352 FE is my choice with the adapted "L" bracket for the old gen mount below the pass head.
Appreciate the assistance hope to get the package together this week...
2 piece bracket set CRAP
Alternator suggested above
3 wire pigtail
power feed for battery 6 gauge at least with inline fuse
v belt pulley swap req. ? gen has 2 pulleys are they usable ?

Steve M.

[simplyconnected]

...v belt pulley swap req. ? gen has 2 pulleys are they usable ?..

Yes, if your generator has a pulley you want to swap, they bolt right on to new alternators. Make sure you retain the small bushing on your alt, otherwise the new pulley will scrape the alt case.

[lake bird]

conversion underway

started the conversion, generator and voltage regulator removed...just folded unused wiring back into front harness, taped it in. mounted a 6 bladed fuse box where the volt reg was, for the hot wire and horn feed that was on the volt reg F terminal. can use the fuse box for an electric fan, next phase.
The CRAP 2 piece alternator bracket set wouldn't accommodate the 3 G /130 amp alternator .. had to add a 1 1/2 inch extention to the lower arm ,ask Larry at CRAP to consider making the arm longer....waiting on the rest of the parts to complete.

Lakebird/Rockwall,Tx