SOLVED - 2014 Suburban Electrical gremlins

[Fless]

Those are voltage tests.

Good voltage DROP tests should be very low, not B+ voltage. The point is to read the "potential" between two contact points that should have a very low difference. So loading the circuit and reading the voltage between the two contact points (positive to positive; and negative to negative).

 

[Doubeleive]

That was kind of my thought. I found the oem replacement cable for $64 on amazon but dont want to continue guessing.

I just did 2 voltage drop tests starting the truck.
1) from the positive battery terminal to the engine block ground at the cylinder head. Result was Max 14.9 volts and min 10.68.
2) from the negative battery terminal to the ring terminal at the end of the starter positive cable at the starter. Max was also 14.84 and min was 10.4.

This doesn't seem like a meaningful difference does it?

My next step is to drop the dome light housing and look around in there. Fingers crossed I dont break the plastic

technically 10.4 at the starter is a fail, but unless it's not starting properly then that is probably not the problem
gm considers 10.5v to be the bare minimum
I would move on from the starter cable for now and poke around elsewhere

 

[Fless]

 

[bacon612]

Dropped the dome light. Everything looks new in there.

I did, however, find something curious. If i disconnect the 2 pin connector on the alternator (which i think is the RVC system) Amperage with my mulitmeter reads a rock steady 13.6V. No surging headlights or interior lights. Rock solid. Why?

While i could just keep the 2 wire connector off of the alternator and put up with reasonable voltage with no fluctuations with a 'fix charging system' warninig light, I'd much rather know why the RVC system is causing my problem....

Any thoughts out there?

 

[solli5pack]

Dropped the dome light. Everything looks new in there.

I did, however, find something curious. If i disconnect the 2 pin connector on the alternator (which i think is the RVC system) Amperage with my mulitmeter reads a rock steady 13.6V. No surging headlights or interior lights. Rock solid. Why?

While i could just keep the 2 wire connector off of the alternator and put up with reasonable voltage with no fluctuations with a 'fix charging system' warninig light, I'd much rather know why the RVC system is causing my problem....

Any thoughts out there?

So you unplug the little connector on the back of the alternator and all the problems go away?

 

[bacon612]

So you unplug the little connector on the back of the alternator and all the problems go away?

Correct. Voltage stays locked at 13.6 plus or minus .1 of a volt. No headlight flicker or dome lights flicker. But I get a battery light and a 'charging system' error on the green matrix led screen in the gauge cluster.

I think removing that 2 pin plug, I am disabling the RVC system so that the BCM can't tell the alternator what to do anymore.

 

[solli5pack]

Correct. Voltage stays locked at 13.6 plus or minus .1 of a volt. No headlight flicker or dome lights flicker. But I get a battery light and a 'charging system' error on the green matrix led screen in the gauge cluster.

I think removing that 2 pin plug, I am disabling the RVC system so that the BCM can't tell the alternator what to do anymore.

That's interesting. When I get some time I'm gonna check to see what All Data has on the RVC system. Does it have it's own ground somewhere?

 

[Doubeleive]

That's interesting. When I get some time I'm gonna check to see what All Data has on the RVC system. Does it have it's own ground somewhere?

the rvc system goes into default when the clamp sensor around the main ground cable is disconnected
so OP you might try doing that and see what happens, if the sensor is bad it might not be throwing any codes but you would be able to see the rvc system status with a tech2
it's going to show the mode commanded when you do certain things like turn on the windshield wipers or headlights/ac etc,
I fought with mine quit a bit and finally discovered I had a bad battery that was causing a problem from all appearances the battery passed testing but was borderline and would not properly charge, making the rvc system think it was fully charged and lower the alternator output even even commanded to full power.

 

[mikez71]

Check out the note on circle at the top...

 

[bacon612]

the rvc system goes into default when the clamp sensor around the main ground cable is disconnected
so OP you might try doing that and see what happens, if the sensor is bad it might not be throwing any codes but you would be able to see the rvc system status with a tech2
it's going to show the mode commanded when you do certain things like turn on the windshield wipers or headlights/ac etc,
I fought with mine quit a bit and finally discovered I had a bad battery that was causing a problem from all appearances the battery passed testing but was borderline and would not properly charge, making the rvc system think it was fully charged and lower the alternator output even even commanded to full power.

Couple things...

I bought an oem negative cable in the senseless pursuit of throwing money at parts to solve this issue. The delco negative cable comes with a new clamp sensor.

In my case, i found that the rvc system would only be disabled (or default as you say) when i disconnected the 2 pin from the alternator. When just disconnecting the clamp sensor, my voltage output was still high 14s and into 15s. Im now curious if theres a way to test the wire between the clamp sensor and the BCM (or wherever it goes). Would the clamp sensor throw a CEL if it was bad?

Interesting about the bad battery. When this issue began, i started by replacing my AGM (Costco) Iterstate battery that was a year old. I got a new Interstate AGM from costco. Same result. Then i swapped that for an Interstate Flooded (also from costco) and thats whats in there now. None of these swaps have shown me any progress in solving the issue. I did read, however, that generally speaking, you are suposed to replace batteries in these trucks with what came in them from factory. Which is flooded. Who knows...

Ive attached 3 screenshots below that have educated me about how the RVC system operates