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VCM Problems

557 views 5 replies 5 participants last post by  sabor 
#1 ·
Hello,
I have a question about the VCM I bought from you a while back. I always set it at 14.9 because I have a xs power batt. I also have it set in the back to not go over 15.2 volts. On start up it flutuates to 15.5 or so. Anyway I thought it is supposed to remember the 14.9 that I have it set at like was explained in your video. I stopped to put in gas and when I started the car the vcm was set to 14.4 and I had to reset it to 14.9. This happens almost daily.
I have a DC 270XP alt which works fine and is supposed to be compatible with the vcm. So what's up? thanks
 
#2 ·
What you are experiencing is normal. The VCM does not regulate voltage, it simply "stacks on" additional voltage on top of the regulators set point. Most any GM regulaotr (stock, DC power, MechMan) Will start off around 14.8 - 15.2 volts cold. As the temperature of the alternator increases, the setpoint of the regulator is lowered to prevent alternator and battery overheating. This is a feature that is built into almost all internal voltage regulators. The VCM does not change that feature, it merely gives you the ability to add a set amount of voltage on top of that curve.

When I start my truck up on a cold morning, I see 17.2 volts, once the alternator comes to temperature it falls to 16.5 volts, and that is on a Stock 105 amp Valeo GM alternator.
 
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