heater problems

Sounds like a mode door motor is inop. Very common on these vehicles. The key is finding where it is located. It could be the one behind the glove box. The motors are not very expensive. Accessing them can be however. This is not a fuse issue

Hey Cameron .. my heater motor quit on my last night .. how expensive are they? And .. unfortunately I saw you messaged they are not easy to get at. Where abouts are they? Under the dash on pass side? Cheers

I would recommend rolling all the windows up, with the vehicle and radio off and the blower on the lowest speed attempting different mode settings. If you can hear a motor noise, popping, tapping, etc than more likelier than not you have a broken mode door which means your removing your dash to get to the HVAC case assembly (not fun). Odds are the actuator is ok. As to not blowing at all, it could be a shorted blower motor, blower motor resistor, fuse, short, etc. If youre exhibiting all these things, you could also have a blown heater core which is causing all these issue. Remove the glove box door and behind it should be your blower motor resistor. Remove it and inspect for coolant. Also, you might be able to see the mode door concern as well.

Dont for get the system is vacum so you might have a vacum leak thats why it wont swith over settings

We have a gm 1999 Envoy and everytime we try and put on heat all it is blowing cold Air? is there a fuse or it is the heating system?

I think that a piece of the plastic dash vent is blocking my air blend door from opening and letting the heater work