Help;
I have installed a Uni-Line 721-008 pilotless system in my 1979 Rheem
RRAB-08E48JR rooftop HVAC unit.

I have 3 original wires to hook to the new unit that has 2 wires (black and gray) remaining to be wired. 1 original old black wire comes from the transformer into the heater compartment and measures 18 volts (open) to unit metal ground.

2 original old white wires go from the heater area into the blower compartment; they both measure 4 volts open to unit metal ground.

Originally, the old black wire was attached to terminal S on the old gas valve, and also to the pilot relight.
1 old white wire, coming from the blower compartment, was attached to COM on the old gas valve.
The other old white wire, coming from the blower compartment, was attached to L on the old gas valve, and also to the pilot relight.

Any ideas on how to correctly wire these wires?

Thanks

First you better make sure that Robertshaw control will work in cold temperatures (low ambiant conditions) as winter gets brutal on roof top units.

Follow the manufactures install instructions for the valve install.