Customer is really concerned because he found yellow residue inside The water condensate system and it feels oily, explained to him we could have a service technician out here but does not want to pay the $78 fee to get a technician out here. also clean the water condensation system for customer. And told him to keep an eye out to see if it’s yellow again and if it is to get a service technician out here. Furnace is working excellent. Recommend a surge protector to protect his investment.