I installed a 130 amp high output alternator from Maniac Electric Motors on my EM1.

I also have a 4 gauge wire from the alternator to the pos battery post (stock power wire is in place)

The problem I'm having is that when the car is first started cold, the alt is pushing 14.x volts. Once the car is warm, it's 12.3 volts...

When I raise rpm's the 14.x voltage output is achieved.

The problem is that the voltage does not seem to raise when accessories are turned on at idle speed. And my headlights are noticeably dimmer than they used to be.

I have the stock ground wires, but they are all brand new and properly installed.

Does anyone know what could be causing this behavior? I'm going to call Maniac tomorrow, but thought maybe I could get some insight before I do so.

Is there any way adding an additional ground could solve this problem?

Also, when I upgraded my 93 Mustang's alternator, I left the factory power wire disconnected and haven't had problems there.... could that be causing an issue?

Thanks,
Jason

 

When you turn the key from off to ON(II), does the charging system warning light in the cluster turn on and stay on?

Does the light turn off and stay off after the engine is started?

 

Yes and yes. While running, the charging light has not come on at all.

 

Any CEL codes, like code 20?

 

Nope, just 65 for a bad secondary o2.

 

Code 65 is for the the heater element of secondary O2 sensor. The heater element gets voltage from fuse 15, which also protects the alternator/voltage regulator circuit. You may want to look into this.

 

Fuse 15 in the interior fuse box is good, just checked it.

Thanks a lot for your help so far. Any other thoughts?

 

I was suggesting that the cause of code 65 might possibly produce voltage fluctuations that could discombobulate the alternator voltage regulator.

 

If fuse 15 is OK then what else could be causing code 65? The code existed before I installed the alternator.

 

It'd be pretty easy to Ohm test the heater element and its 2 wires.

 

This couldn't be causing my issue could it?

 

Yes. In simple terms, your electronic load detector(ELD), among other things, use the same circuit as the heater on your secondary o2 sensor.