Possible voltage regulator issue

So I have a new alternator and battery. When hooked to a computer it is saying voltage regulator. But in one of your answers on this site you said the computer is very reliable and it should be the last thing to replace. So what should I do? Is there a fuse that may be bad? Is there something else that could be wrong to give it that reading of "bad voltage regulator"? The computer is $200.00 or more to replace. so hoping there is another way to fix the voltage regulator without installing a brand new computer all together. Please help!