1978 Caprice with a stock 2004 Avalanche engine and trans.

The car is over charging at 14.9-15 volts at idle. I've measured at the battery with the engine off (normal 12.xx voltage) and engine running (same as volt gauge in car - 14.9-15v). Below is a picture of how I have the alternator wired. Am I missing something in my setup that would be causing this?

 

Most modern alternators have built-in regulators. I think yours does, and I bet it's malfunctioning.
BTW I think running welding cable from the alternator to the battery is way overkill. From battery to starter, yes, as a starter amp draw warrants it. An alternator does not move that many amps to warrant such heavy cable.

 

Well, I adopted this drawing quickly from a previous drawing I made and I actually omitted that the welding wire also carries the entire fusebox as well as the relays for the cooling fan, etc. Even so, it's probably a bit much but I didn't want to ever have to worry about the load so I just went big. I'll try to look up a way to test the regulator online.

 

Is the alternator receiving a voltage reference signal?

 

I would put the alternator output wire to the starter, not the battery. I would also add a wire to the S terminal of the alternator and connect that to wherever you have your main power distribution point, in your case, to your power bus of your big Bussmann fuse and relay box.

Andrew

 

I've been reading numerous threads on this and I'm finding a lot of information that says that 15 and under is OK. Mine is right at 15. This still seems high to me. The battery has been charged and checked so it is not low and all the connections and wires are new so there's no bad grounds. I'm trying to find a description on how to test for an overcharging alternator other than taking it off and taking it to an AutoZone. Does anyone know of a good write up?

If the alternator wasn't receiving a voltage reference signal it wouldn't be charging at all, correct?

What is the reasoning for connecting the alternator output to the starter instead of the battery and adding a terminal to the S terminal?

 

It simplifies battery connections, plus one less battery connection to corrode. Wire to starter, cable between starter and battery. The way it's been done for ages, because it WORKS.

 

I just checked the voltage between the alternator output terminal and the alternator case and it was 14.6. I turned on the headlights and the hvac blower motor to full and it dropped down to 14.5. This sounds normal to me. I checked the dakota digital dashs numerical readout (i have analog gauges) and it's saying 14.9.

Is it possible the dash would read 0.3-.4 volts higher? I'm not sure why this would be the case as I believe all of these dashs are tested at the factory and if anything the voltage drop should be lower but maybe this is something that's common. Given these findings I would say my charging is fine and I'll just need to remember 14.9 is really 14.6.

 

Actually a lot of Chevy's were wired this way from the factory. His probably was that way already.

 

If this is true, then I say you are fine. Maybe the gauge is not reading correctly? Voltage output will be highest at the alternator stud, so I don't see how it can be higher at the gauge.

Andrew

 

Yea, I'm not sure. I'm curious if others with a Dakota Digital dash have had a similar experience. At least I don't have to chase down another issue.

 

I don't have first hand experience with their products, but some the people I know have had mixed reviews. I love the way their gauges look. I think they do an incredible job with the visual element, but in terms of functionality, they seem to be hit or miss. My buddy Paul has their gauges and a Holley Dominator. DD makes a box that will hook their gauges with the Dominator via CAN. Sounds great, but his experience can be read here:

https://forums.holley.com/showthread...l-Oil-Pressure

It looks weeks to get a tech that would actually escalate the issue.

Andrew

 

Depending on what you are using to read voltage and where you are reading it from could also be the difference between your readings.

I installed a DD digital gauge cluster in a car for someone and HP Tuners read one voltage from the OBD II bus generated by the PCM, the gauges read another voltage, my Fluke DVOM read a third and another DVOM I have on hand as a backup had a slightly different reading. The Fluke, other DVOM and the GM PCM were close to each other while the DD cluster was the farthest off base. In DD's defence, their voltage display only had a single digit past the decimal but I remember thinking it was a little optimistic.

In short, I trust a Fluke or other quality DVOM and the output directly from the PCM before I will trust anyone's gauge cluster I don't care the cost.

 

I have a Dakota Digital VHX cluster in my 72 El Camino and it too reads right at 15. I have been running it for over a year now.

 

Have you ever checked the voltage readings at the alternator or battery to see if the gauge is off?