Selecting a proper alternator for your Fox Mustang build will be a crucial part that you will need to consider. This will also include all associated parts that go along with either a stock or aftermarket upgraded applications. Within this Fox Body Alternator Buyer's Guide, we will cover everything you will need to know for your build!
|SUGGESTED USE||FACTORY HARNESS MODIFICATION?||POWER WIRE UPGRADE?||BRACKET MODIFICATION?|
|75 AMP||Factory Replacement||No||No||No|
|95 AMP||Step Up From Factory||Yes||No||Yes|
|130 AMP||Needed For Electric Fans or Aftermarket Stereo||Yes||Recommended||Yes|
|200 AMP||Great For Electric Fans + High Demand Stereos||Yes||Required||Yes|
A 1G to 3G upgrade is perfectly fine for the 1979-1985 applications. When completing this upgrade, a new replacement external regulator box will need to be added to capture the proper circuit and retain the stock wiring harness along with a 3-wire (3G Series) regulator plug wired into place. This route will allow you to retain the OEM warning lights and shunt-type ammeter on the vehicle dash.
Upgrading the power wire is not always needed in all cases. The 75 and 95 amp options do not require this upgraded power wire. However, installing this on any of the 130 amp options is recommended, and it will be 100% required for all 200 amp configurations.
Watch this installation video and follow along as we show you how to replace your factory alternator with a SVE 130 Amp Alternator Kit. Get a charging system in your Fox Body Mustang that is ready for all those power robbing mods you want to add such as electrical fan and under drive pullies! more
For this install, LMR is going to cover how to upgrade to SVE's latest 200 Amp Alternator upgrade kit. This applies to all 1986-93 5.0L Fox Body Mustangs. more
Why is this important to know? Often, the combination of performance parts can result in your upgraded alternator not charging at its idle RPM. The 130/200 amp alternators need 1800-2000 idle RPM to make power. IMPORTANT: this is shaft RPM and not engine RPM. These alternators will produce maximum output at 6000 shaft rpm but will fail at 16,000+ RPM.
Steps To Calculate Shaft RPM
To determine the max shaft RPM, take your max engine speed (for example, 5800 RPM) and multiply it by the calculated ratio you figured above (5800 x 2) = 11,600 shaft RPM. To determine the idle shaft RPM, multiply idle RPM x Ratio (for example, 1000 x 2) = 2000 shaft RPM @ Idle. Note: lower output alternators require less shaft speed at idle to perform.
The manufacturer recommends the following:
If you have upgraded to a 3G alternator in your Fox Body Mustang and are still experiencing charging issues, here are some of the best places to start. Don't forget to check to ensure your alternator is also idling at optimum RPM to charge.
** Never under any circumstances remove the battery cable while the car is running! Doing this can damage the internal voltage regulator making the alternator no longer charge. This test only worked on early cars with a very low draw and an external mechanical voltage regulator. **