Rheem valve or board

russiand

Rheem R95PA furnace, blowing cold on heat call. Spark super brief and not lighting. Unscrewed the spark ignitor left it grounded to see how it looks. Sparked for split second. Took the leads off the White Rogers gas valve 17volts AC and then 27 when it tries. As soon as the leads came off the valve, spark became long and stronger as normal. I am lost as cant make the call on whether board or the valve.

SuperTech

I would put a 24 volt contactor in place of the gas valve for troubleshooting purposes. If the contactor closes when the gas valve is energized and the spark remains normal you know the problem is the gas valve.

I would test it again with the leads disconnected. Is this an intermittent pilot system? You should measure at least 24V between PV and MVPV when the pilot is lighting. If voltage and the spark is different with the gas valve connected you might have a faulty valve

russiand

Direct spark ignition there is no pilot just two leads to the valve

HVACNUT

What's the Lockup and manifold pressures?