Voltage Regulation - How?

01Burb · January 9, 2004

My voltmeter keeps going up to 19V - the battery light comes on when it does this and the headlights get waaaaaay bright..

Sounds like the voltage regulator. How does that side of things work on these trucks?

Any other ideas?

Thanks fellas.

bomber · January 9, 2004

It's built into the alternator.

Repalce the alternator it's cheap enough.

robsawatsky · January 9, 2004

Yup, had this happen in my old 1990 Ford F150 - voltage would swing way high and then way low. Replaced the alternator with a remanufactured unit.

01Burb · February 5, 2004

OK..I have replaced the alternator with a new one. I also have a new battery which is fully charged.

I'm driving along and the voltage will swing up to 19V for sometimes 30 secs and then return to 14V. I think I really need an auto electrician here. What are the three white wires going into the alternator and what do they do?

What can be causing an overvoltage? Something is telling that regulator to pump out 19V

stlmaj · February 5, 2004

This still sounds like a voltage regulator problem you should replace the alternator again. It should still be under warranty. If you installed one of those remanufactured ones I wouldn't hesitate to replace it again!! If the voltage spikes continue with another alternator then I would suggest looking further into it. But just having a reman one go bad that fast is not all that unusual.

Matt

intruder217 · February 5, 2004

Do you believe your guage?

01Burb · February 5, 2004

Do you believe your guage?

Yes because the voltage increase causes the HVAC fans to speed up and at night, my headlights get brighter.

In addition, the airbag light comes on and the steering gets light - I assume that the power steering has some electrical component or maybe the pump rotates faster and makes the PS light.

When it cuts back to 14V I hear some relays dropping in (or out) under the steering column.

The alternator is an GM unit not a cheapo and was installed by the dealer. As well as the main output terminal there is a plug with 4 terminals labelled P,L,IF and S. The S wire goes to the output terminal, I assume that is the sensor that reads the reference voltage. The L and IF have wires that dissapear into the loom. The P is not used.

Can someone tell me the function of the L and IF wires. I assume one goes to the dash idiot light.

I 'rewired' the 'S' wire and checked all my grounds including the alternator ground which is good.

Help.