A local guy who I usually do HVAC work on the side for has a Raypak P-R406A-EN-C Natural Gas pool heater. He went to fire it up the other day and it won't light up. It will turn on and you can here the ignitor clicking but it won't light. I pulled that out from inside to see if it was sparking and it is and seems like a good spark. One thing I noticed was there wasn't any smell of gas, like as if it isn't getting through. I checked all valves/feeds to the unit, everything is open, cleaned off the burner tubes in case dirt was blocking them but no luck. He didn't have a manual but I was able to find one online. I'm getting good voltage everywhere it should be for low voltage and high voltage I believe. However it mentioned checking these 2 terminals on the circuit board behind the display. It said to check for 24 VAC across PV-MV/PV terminals on the PC Board. If voltage is okay, replace gas control; if not, replace PC board. I do not do hardly any service work and electrical is my weak point. I mainly do new installs. When checking with a multi-meter I want to put a lead in the PV terminal and one in the MV terminal and I should read out 24v? Or do I want to check each terminal with one lead in the terminal and the other lead in like a Common terminal?