Weird charging issue. Have to rev over 3K to show charging.

[pjmoreland]

Originally Posted by gmc684x4

One of the many reasons I upgraded to a 10si alt 3 decades ago and upgrading again to a cs144

I ordered a 12SI and plan to install it once it arrives. I am concerned the 12SI may have the same issue though if the issue is caused by my wiring.

[RichardJ]

Blue, White, Brown only confuses things. If by Blue you are talking about the Field wire and it connects the F terminal on the Voltage Reg, to the F terminal on the Alt, then we are talking about the same thing,
The R terminal on the Alt connects to the #2 terminal on the VR,

>>the white wire is supposed to use voltage generated by the alternator (isolated from the battery voltage by a diode)<<

You have a diode inside the VR?
The Alt has three pairs of two diodes. You have ~ 12V at the top of the pairs. In the middle of the pairs you will have 1/2 of the output voltage. 6-7v depending on the 12 - 14V output.

The R to #2 wire should have 6 -7 Volts. White, Maybe.

[pjmoreland]

Originally Posted by RichardJ

Blue, White, Brown only confuses things. If by Blue you are talking about the Field wire and it connects the F terminal on the Voltage Reg, to the F terminal on the Alt, then we are talking about the same thing,
The R terminal on the Alt connects to the #2 terminal on the VR,

>>the white wire is supposed to use voltage generated by the alternator (isolated from the battery voltage by a diode)<<

You have a diode inside the VR?
The Alt has three pairs of two diodes. You have ~ 12V at the top of the pairs. In the middle of the pairs you will have 1/2 of the output voltage. 6-7v depending on the 12 - 14V output.

The R to #2 wire should have 6 -7 Volts. White, Maybe.

I don't have a diode in my voltage regulator. I was referring to the diodes inside the alternator.

My alternator doesn't have F and R on it. Instead, it has 1 and 2. White goes to 1, and blue goes to 2.

On the voltage regulator end, blue is F, and white is 2.

I am concerned about the behavior of the white wire (VR2 to alt 1). When I first start my truck, the voltage on it is only 0.1V. If I increase the rpm slowly, the voltage increases steadily until it gets to 0.6V. It sticks there as I continue increasing RPM until it jumps suddenly to around 5V, and immediately jumps to 14.8V and stays there after I let the engine idle down.

The blue Field wire starts out at 11.7V at idle, and then drops to 8V after revving.

Voltage measured at the battery is 12.5 at initial idle, and jumps up to 14.5 after revving and is stable at 14.5 regardless of the engine RPM after the initial rev.

[Steeveedee]

Originally Posted by pjmoreland

I don't have a diode in my voltage regulator. I was referring to the diodes inside the alternator.

My alternator doesn't have F and R on it. Instead, it has 1 and 2. White goes to 1, and blue goes to 2.

On the voltage regulator end, blue is F, and white is 2.

I am concerned about the behavior of the white wire (VR2 to alt 1). When I first start my truck, the voltage on it is only 0.1V. If I increase the rpm slowly, the voltage increases steadily until it gets to 0.6V. It sticks there as I continue increasing RPM until it jumps suddenly to around 5V, and immediately jumps to 14.8V and stays there after I let the engine idle down.

The blue Field wire starts out at 11.7V at idle, and then drops to 8V after revving.

Voltage measured at the battery is 12.5 at initial idle, and jumps up to 14.5 after revving and is stable at 14.5 regardless of the engine RPM after the initial rev.

That is an internally regulated alternator! Do you have a regulator on the radiator core support too, and how is this all connected?

[pjmoreland]

Originally Posted by Steeveedee

That is an internally regulated alternator! Do you have a regulator on the radiator core support too, and how is this all connected?

I do have an external voltage regulator. If I do a search on the alternator part number 1100569, the results say it is a 10DN. Isn't the 10DN externally regulated? I am confused by the connector style though, because it doesn't look like the OEM from a stock alternator from our trucks. The previous owner installed this alternator.

[pjmoreland]

Could it be that the front housing of my alternator that has the part number on it is from a 10DN, but the internals and rear housing are an internally regulated unit??

[pjmoreland]

Originally Posted by Steeveedee

That is an internally regulated alternator! Do you have a regulator on the radiator core support too, and how is this all connected?

Thank you, Steeveedee, for pointing this out. I just installed a 12SI alternator and a jumper block in place of the regulator, and the voltage jumps right up to where it is supposed to be as soon as I start the engine.

['68OrangeSunshine]

I had this same gripe on both of my trucks this summer. On the '71 GMC Jimmy, I put on a 10SI Alternator -- jumping F with #3, and #1 [Red] with #2. Works great. Ordered a brand new Alternator for a '77 Blazer.
On the '68 C/10 w/292, I cannibalized an EVR from my '67 K/10 Suburban parts truck, that was new in May '97.
The EVRs they give as ''lifetime warranty'' replacements are new junk straight from the box. Both O'Reilly's and NAPA have given me junk.
But an EVR from 23 years ago still works great. Go figure.

[Steeveedee]

Originally Posted by pjmoreland

Thank you, Steeveedee, for pointing this out. I just installed a 12SI alternator and a jumper block in place of the regulator, and the voltage jumps right up to where it is supposed to be as soon as I start the engine.

Excellent! That picture was worth a lot of pages...