While working on coach recently, (cold here) my CO alarm went off, so I shut off heat and opened windows and vents and left. Next day I shut up everything as before and ran rear heat for a wile and all OK. Then shut of rear and turned on front heater and after a bit, the CO Alarm went off again. Did the window and vent thing again, and then proceeded to pull out the front heater.



I'm now trying to decide whether to replace heater with a variable output unit (about $650) or just 'cap it off'

'It's always something'

This is exactly what happened to mine. I replaced it with a two stage unit and am very happy with it. For most of the time it will run on low speed (low output) and is much quieter then on high speed, high output. I shopped around and got mine for about $450. This was for a 35K/18K BTU unit.

Make sure you check all the heat ducts to insure there is no restriction and that there is the needed amount of square inches of outlets. For mine I needed 48 square inches (4 4" ducts), originally I had only 3 1/2 ducts. 3 were a full 4", 1 was completely blocked, and the one in the bath was reduce to 2".

Without adequate air flow, the burner will get much hotter and burn thru as yours did. Yes, there is supposed to be a air flow switch BUT, these do not fully protect the burner housing.

HTH

Wow. Thats when you're happy as can be that things are working as they should (CO alarm) to alert you. If it wasn't for that, I don't want to think what the results could have been.

Thanks Ed for info on ducts, I have 4 4" ducts, 2 under the couch, and 2 under the kitchen cabs. They may be crushed though, I'll make sure they are good.
The least expensive unit I could find, that I would want, is at Tweetys for $642 with free shipping. Do you remember any details on one less expensive?
Thanks

Wow that brings back scary memories. I have a 1950 36x8 trailer we made into our deer camp. We put in a CO2 detector and every time you would go out the door the darn thing would go off. We thought the detector was defective. Why would fresh air make it go off. Well I pulled the heater and replaced with a direct vent heater and was going to use the other one at home in a shed. Took the heater all apart and there was a crack running the entire height on the inside of the heat exchanger. You couldn't see without a mirror and the crack was 1/2 wide . No wonder the CO detector went off when you opened the door. It messed the draft and back drafted into the trailer. How we are alive is amazing. Be careful with your heaters and water heaters. You only get one life. Unless your a cool cat

OK people, we all know that CO2 is carbon dioxide which is the fiz in your soda drink, and in that frosty fire extinguisher, and what happens when you exhale, and that CO is carbon monoxide which is odorless and tasteless and will displace oxygen and kill you which is a not a good thing.


HTH

You got me Jack Carbon Monoxide not dioxide. Who would want a cold frosty without fizz?