I got a call today for a youk unit m#: D4CG036N09225 not heating. Went up to the unit and found that it was not sparking. Had 24v to ignition controller, combustion fan running, all limits/rollouts switches closed. When the relay in the ignition control clicked, you could hear barley hear the spark. Tried to clean up the burner, sanded the pilot tube near the sparker and tried to light it again, no luck. I figured that the ignition controller was bad and not providing the spark necessary to light the pilot. Picked up a new ignition control, spark igniter, and flame sensor and installed them. The unit fired up and ran for a few minutes then shut off the burner, combustion fan still running. Main fan running and roll out switch still closed. Tried to fire it again and got the same weak spark that i seemed to be getting before. Had to leave the site because the business was closing and need to return tomorrow. I'm thinking it could be a grounding issue, but i did clean the grounding terminals on the gas valve. I did swap the placement of the sparker and flame rod, and the spark seemed to be good, perhaps it it a spacing issue with the new sparker? Has anyone had this problem before on an older your unit?