VCM reading way off, why?

[AMI CUSTOMS]

I have been noticing lately with just one alt connected to the vcm, I am getting some way different readings on voltage then at my battery bank. What is going on? I havent got the DMM out yet but plan on it this weekend to see what is up and clamp my alts too, so I can see if something is going on there. I have three alts in the truck right now, one on VCM and two just on factory regulator plug. Voltage at bank will be 14.7 cold and VCM reads 15.9, once hot it will come down some but still .5 or greater difference. But here is what is weird if I plug all three alts into VCM I get exact same reading at bank, 15.0 at bank, 15.0 on VCM once hot. If I do this cold, here is the weird part, VCM reads 15.0 and bank reads 15.3 ??? LOL

All bank reading are with two stinger volt meters, at two different spots in the bank, both read the exact same.

So, what is going on here? LOL

[Nathan @ XSpower]

Could be the VCM, could be a lose connection, or could be something else. No way to tell without checking it with a volt meter.

[AMI CUSTOMS]

Update, well this past week, I checked the connection points of the VCM, perfect. Did some testing and noticed that with all three alts connected to the VCM, two where charging at 15.0 and one was at 15.4? Is this because not enought load on them so the voltage isn't matching? Also ambient temp was over 100 degrees, motor was at 210 operating temp. I did get the current clamp out and noticed only 60 amps on each alt.

[Nathan @ XSpower]

Guessing that was with no load on the alts? Was the 15.4 alt in the stock location and the other two in the secondary positions?

[AMI CUSTOMS]

Yes the 15.4 was the alt in stock location and yes very little load on the alts.

[AMI CUSTOMS]

So we good then? Or something else I should look at?

[Nathan @ XSpower]

Have you checked to see if the two alts hooked to factory wiring are actually working? What did you have the VCM set to when it was reading 15.4?

[AMI CUSTOMS]

I changed out batts and now it is reading alot closer, .3 of difference all the time, with only one alt being controlled by VCM, will all connected no difference. Think it might of been that the batts needed a charge.