cema93

I bought a 1989 5.0 last July and have been trying to work out a few kinks. I replaced the alternator iwht a SR 130 AMP alternator from AM. While installing we actually were able to identify a few flaws in their instructions which i think helped fix them Anywho, I watch the battery gauge and it fluctuates so easily. And what i mean is, I can see the needle bounce with the turn signal, I wont have headlights or radio or AC on. I was hoping this new alternator would help make the electronics stronger...was i wrong? Does the voltage regulator need to be replaced?

dawson1112

So you did a 3g mod? Meaning you upgraded from a 2g alt to a 3g alt. Im pretty sure that the 3g alternator has the voltage regulator built into it.

You may want to rethink changing the install instructions.

cema93

The install instructions were for a different brand/type. AM agreed and got us the right one.

I think we did a 3G one. Im just wondering why the voltage fluctuates so much (turn signal, headlights, wipers, window motor)

88 orangepeel notch

I'm with Dawson on this. I don't know what part of the instructions you changed to "fix" them, but I'd go back and rethink those.

I just did the 3G upgrade last summer, with the LMR kit, and I followed the instructions to the T. And I have no fluctuations at all. No matter what accessories are on at idle.

EDIT: Just out of curiosity, throw a meter on the battery and see if it really is fluctuating as the gauge says.

Chromeshadow

+1
Btw, fast fluctuations that dip under 13.6 V are usually a result of a weak battery or poor connections.
Your dash meter will not have the accuracy you need, using a good meter will tell you more, but digital meters usually only update 4 times a second, so they may not give you all the info you need. You can use both together to see both an accurate voltage reading and the V fluctuation level.

cema93

you guys really don't get it. the instructions were wrong. incorrect. physically impossible. we called American muscle and asked them about it and they got us the correct instruction guide and thanked us for identifying the mistake on their website. I did not "change instructions". I followed the incorrect guide to the point of physical impossibility and called AM. They agreed it was wrong and got me the correct one and from there we were able to get the alternator installed correctly.

cema93

chromeshadow, I will get after it with a multimeter and see what happens and double check all the connections. Also will see if battery is weak. This might seem obvious to you: I left the headlights on the other day for roughly 30-45 min and the car wouldn't start. Turn the key and I would get clicking. Battery dead..

88 orangepeel notch

Ohhhhh, now I get it. Thanks for clarifying it.

Let us know how the battery checks out, and the running volts at the battery.

cema93

I guess my question is why is it fluctuating so much?

88 orangepeel notch

What RPM is your car idling at ? If it's 700 rpm with a little surge up to 900 rpm, then your gauge may show a little fluctuation. At that lower rpm, the alternator isn't putting out enough juice.

If your idle is rock steady at 900, then I'd verify your voltage at the battery with the car running, should be 13.5 - 14.3ish volts.

If your gauge is spiking ( very quick movement) then I'd start with the alternator wiring and battery cables. Clean/tight connections, especially the neg. battery cable to the block connection.