We had a Class C. Driving to Yellowstone, it went off about Denver. We figured it needed replacement (the MH was 4 years old), so we stopped at Walmart and bought a new one. Installed it in the Walmart parking lot. About 30 minutes later, the new one went off. We went to an RV dealer who sent us to the Ford shop he uses. The Ford shop, when told we were traveling cross country, pulled a tech off of a commercial truck she was working on to work on us. (Considerate of the dealer.) After about an hour she reported that the doghouse had been improperly installed (that is on me) and was leaking CO past the gasket. Kept the MH for another 7 years and it never went off again. (I also never had occasion to take the doghouse off again.) :B