Hey guys this is only my second post but I just replaced my heater core earlier today and my defrost dosnt work, you can feel all the air bursting out from where the heater core is and I know there are the flaps (I only see 2) which are in place. The metal door that opens and closes from hot to cold works great I don't know if there is a defrost tube not hooked up or something like that, thank you in advance for any help.

 

If you've got an early/mid eighties car with AC ( or any 90-92 ) then it's possible that you knocked the vacuum line off. The vacuum line to the blower 'mode' system is a black vacuum line leading into the pass compartment inside the heater/AC wiring harness. It then gets plugged into a Purple vacuum hose that leads to your heater controller.

If it's properly connected on the inside of the car,... go under the hood and be sure that the other end of the vacuum line is properly connected to engine vacuum.

If vacuum is OK everywhere, you could have a stuck flap inside the box ( dead mouse in the way ? ), or a vacuum problem at the controller.

If your car has an 82-90 AC delete heater box than the "mode" is cable controlled - not vacuum. Could be a busted cable,.... busted cable lever @ the box, or a stuck flap inside the heater core box.

 

Okay thank you, do you think I can get to the vacuum line in the dash without taking off the dash?

 

Yes,... You SHOULD be able to access it. ( no telling after the heater core swap ) You can usually get to the interior vacuum lines by reaching behind the center console on the drivers side.

 

Okay thank you!

 

When I replaced my heater core, I couldn't find the last bolt on the heater core box cover so I ripped it out and broke it since that is not on is that the reason for the defrost and heater etc not working because it hits the cover and goes to where it is directed? Should I buy a new cover? Thanks