[Snowflakes]

I have a coleman 3800 that sometimes it blows hot air and sometimes its cold, could it be the thermostat, although it was changed recently,

[hvac1000]

You need to keep your posts together under the same name!!

It sounds like you have a intermittent problem so it could be just about anything.
If your furnace has a flame sensor try cleaning it.
Look at the sticky notes at the beginning of this board for more info.

Is this in a mobile home?
Is this in a travel trailer?
I have no listing for a 3800 series Coleman.