[cal66gt]

I've just completed a lot of upgrades, new Edelbrock electric fuel pump, new Spal 16" electric radiator fan, and March Perf 6 rib belt bracket and pulley system (not serpentine).

The two new electronic upgrades require more amps than my current 3 wire 100 amp alternator can provide. During the day it's been fine, but tonight when I turned on the headlamps, the motor started to stall at idle. Reading through some old posts, I'm guessing my alternator isn't putting out enough power at idle and it's probably not powering the fuel pump.

These same prior posts had a lot of interesting discussion on whether or not to use 1 wire or 3 wire, GM versus Ford, 1G or 2G, or 3G, all interesting but nothing I could find about what alternators actually put out high amperage at idle.

Has anyone done similar upgrades and updated their alternator? If so, what brand/model did you go with. I don't want to go just with the factory amp rating, I want to make sure I'll get high amps a low rpms.

Thanks in advance

 

[roadrunner spain]

Hi, your 100 Amp. alternator should be fine. Even newer cars with power windows, fuel injection, Xenon lights, ..... have smaller alternators. If you don´t have big electrical consumptions like a sound system, your alternator will work.

Check your cables on connecting points and the main cable from alternator to battery as well. Previous owner of my car replaced main cables, but they were too thin. Had problems at night times as well.

If you think your Problem is fuel pump, it´s easy way to find it out. Disconnect your fuel pump from electrical system of your car. Connect it to a second, undependent battery. Start engine and switch on all electrical units.

Good luck

 

[cal66gt]

Hi, your 100 Amp. alternator should be fine. Even newer cars with power windows, fuel injection, Xenon lights, ..... have smaller alternators. If you don´t have big electrical consumptions like a sound system, your alternator will work.

Check your cables on connecting points and the main cable from alternator to battery as well. Previous owner of my car replaced main cables, but they were too thin. Had problems at night times as well.

Good luck

Roadrunner, thanks for the input. I'll go do some investigations on connections I've not checked in a while. Also, I'm adding up a power budget of my running items, biggest draw is the electric fan that can draw up to 50 amps on start up. The fuel pump, stereo, headlamps, etc all probably add up to another 30 or so amps.

If at idle, my 100 amp alternator (100 amps may be the rating at high RPM) is only putting out part of that, then I can see that I may be starving the fuel pump. I think more than total amperage output, what I need to ensure is that I'm getting a high level of output even at lower RPM's.

 

[JohnnyK]

I, and I think what most do, is just get an alternator from an sn95 Mustang which is 130amp.

I have a different wiring harness, however, so no help there.

 

[GypsyR]

When you are after high output at lower RPM's, that says 3G to me. A 3G can put out around 40 amps at idle. A GM-type "1 wire" more like 10-15. Not sure what the values are supposed to be, those are just what I happened to have measured on a couple of cars.
At idle your electrical stuff runs off the battery more than anything. With a good battery the alternator could even be disconnected and everything would still run OK. At least for a while. Check or have the battery tested too.
And of course as said above, you may well be having other issues.

 

[Torkman]

What specific 100 amp alternator are you running now. Give me the exact detials, model, year, and wiring hookup you are using and I will see if I can run down some actual specs for you through a buddy who works at an alternator plant.

 

[cal66gt]

What specific 100 amp alternator are you running now. Give me the exact detials, model, year, and wiring hookup you are using and I will see if I can run down some actual specs for you through a buddy who works at an alternator plant.

Torkman, thanks for the offer, but I bit the bullet and bought a Powermaster 140 amp, 3G, single wire alternator. The tech guys at Powermaster were really good, gave me some suggestions to check before buying a new alternator to make sure it wasn't something in my current setup.

As for my old one, not sure of model & year, it was from a donor car and all I know was that is was supposed to be 100 amps, but I'm guessing that may be subject for debate......