Voltage regulator

Tiny
FORDGIRL206
  • MEMBER
  • 1990 FORD F-150
  • 0.5L
  • V8
  • 4WD
  • MANUAL
  • 250,000 MILES
I've replaced my alternator twice, got a new battery and it will run fine for about thirty minutes or so. Then the battery light pops on and my battery drains. Does my truck have an external voltage regulator? If so is this the problem?
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Tuesday, May 21st, 2019 AT 10:03 PM

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Tiny
SCGRANTURISMO
  • EXPERT
Hello,

This sounds like the wiring from your vehicle's alternator to the battery might be having a problem. Think of the battery like a lake and the alternator is a river that is being diverted to fill the lake through a hose. If there is a problem with the wire, it would be like getting a kink in the hose. What happens when your garden hose gets a kink in it. No water. The same goes for wires in an electrical system. So let's see if the wiring is the problem here. To do this you will need to use a multi-meter and a test called a voltage drop test. I have included a link down below if you are unfamiliar with how to use one below:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

I have also included how a voltage drop test works in the diagrams down below. We are going to want to do a voltage drop test on the black wire with an orange stripe going from the alternator to the battery. So with a fully charged battery you are going to need to start your vehicle, letting it idle. Have your multi-meter in DC Volts and put the red test lead at the black wire with the orange stripe on the alternator and one on the same wire at the battery. The voltage should between 13.5 - 15 Volts. If not then the wire needs to be replaced. Please get back to us with what you find out.

Thanks,
Alex
2CarPros
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Wednesday, May 22nd, 2019 AT 2:33 AM
Tiny
FORDGIRL206
  • MEMBER
Before I go buy this tool. The original plug had to be removed because the new alternator doesn't allow for any other plug. It is built in. You connect the wires and crush the metal piece around the wires to keep them in tact. Could this be where we are seeing the short?
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Wednesday, May 22nd, 2019 AT 9:26 AM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

It is very possible. In the wiring diagrams shown earlier there are two different diagrams one with an internal regulator and one without. Could you verify that the right wires are connected together please?

Thanks,
Alex
2CarPros
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Thursday, May 23rd, 2019 AT 6:44 PM

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