Just to stop any confusion the regulator is supposed to supply 13.8 VDC, as this is requirement for radio, depending on the quality of regulation will determine what the open circuit voltage is but I expect it to be close to 13.8 VDC. As part of SAT this voltage needs to be checked and adjusted if necessary and recorded that is was done. I would suggest we look into having an LED lamp to replace this as from my experience they have a much better operating range for variation in voltage and are more reliable.