No heat!?

I have a 99 blazer and the heat and defrost will not work, it blows but cold air. I have changed the thermostat and a couple guys at work seem to think it may be the vacuum intake, which isn't really difficult to get to, but it is a computer chip issue and I do not have an owner's manual. Any suggestions?

I have a 99 blazer and the heat and defrost will not work, it blows but cold air. I have changed the thermostat and a couple guys at work seem to think it may be the vacuum intake, which isn't really difficult to get to, but it is a computer chip issue and I do not have an owner's manual. Any suggestions?

I have the exact same problem, changed the cap, thermostat and just flushed the rad/heater core. Still no heat. The local GM service manager suggested that it could be a vacuum leak, still have to take it in. I fear that it is the heater core (big bucks in labour).

I have the exact same problem, changed the cap, thermostat and just flushed the rad/heater core. Still no heat. The local GM service manager suggested that it could be a bacuum leak, still have to take it in. I fear that it is the heater core (big buck in labour).


Does yours even blow air at all? Mine does, cold air though. I hope it is not the heater core. I have a friend, her hubby works on cars on the side, he has a reader, I am gonna take it to him this weekend and see what he can find.

Sounds like the blending door is stuck.

Quick way to see if the heater core is plugged is to feel the coolant lines going to and from it.

If they are both hot, the heater core is fine and the cause is more than likely the blending door.

If not, the heater core is plugged.

I have the exact same problem, changed the cap, thermostat and just flushed the rad/heater core. Still no heat. The local GM service manager suggested that it could be a bacuum leak, still have to take it in. I fear that it is the heater core (big buck in labour).

Did you flush the whole system or just the rad and core?

Also, did you reverse flush the system?

How did you actually flush it?

A complete reverse flush with some fancy machine at the service centre, they put in that wandeful "DEXCOOL" stuff.

Recently had the same problem with my '99. Checked heater core for blockage, was clear. Changed waterpump and thermostat. Not realy sure if pump was the problem since I still had the problem after the change for a short time. Seems that the system had an air pocket that I had to burp out. Disconnected the hose from the heatercore outlet. Found I had no flow. Disconnecter the other side of core same problem. Added coolant while it was disconnected until the hose started pumping. Reconnected them Bingo I have heat now. Good flow throught the core, since both hoses are now hot.

Hope this helps a bit,

Heli

A complete reverse flush with some fancy machine at the service centre, they put in that wandeful "DEXCOOL" stuff.

Hold both of the coolant lines going too and from the heater core and tell if both of them are hot when the engine is warm.