Responded to a no-heat call for a 2023 Weather King single-stage furnace. Client reported that the furnace runs for a while, then stops, and the temperature drops before it runs again. Found the high-temperature limit switch opening during a call for heat; after a few minutes it would open again due to very high temperature. Fan speed was set to low. Combustion analysis showed 250 ppm CO (air-free), which is too high. Checked gas pressure, 3.5 wc-good. Drain was loose and not connected properly; the condensate trap is hanging below and the hose appears too high. This could be contributing to the high combustion readings. Verified furnace level and slope, which are correct. Recommend correcting the drain trap and reconnecting the hose to the existing drain in the room, as well as running piping from the evaporator coil (AC) since water is currently dripping into the crawlspace. Once the drains are corrected, combustion should be retested. If CO readings in flue remain high, further inve