Expert: Skip Bollinger - 10/11/2006

Question
My 2002 sonoma has no heat. I have a new heater core and a new thermostat. All modes work on heat, air, defrost, and vents. My problem is that I have no heat. I can turn the temp. control up or down and it doesn't make any difference. Yes, the heater core is new and has good flow thru it.  

Answer
Marty,
  Firstly let me explain 2 things. I'm sorry for taking so long to respond. I had some medical problems and had to get into the Hospital for a short stay. Secondly, I'm a Parts Specialist, NOT a tech but I will give you my $0.02 worth.
  My first question is the engine getting to operating temperature? Are the hoses hot? If NOT, you need to find out why. It could be a defective thermostat. IF it is getting hot, feel the heater hoses going into and out of the heater core. Are they both hot? IF NOT, you need to figure out why. There may be an air lock in the heater core. IF there is an air lock, you can take a heater hose loose from the engine and fill the heater core, slowly, with coolant to fill it. Once full, QUICKLY reattach the hose to the engine. IF none of the above pans out, you probably have a diverter door problem. This is a series of doors under the dash that open and close, depending on where you place the Dash Dial, heat, defrost, vent etc. There is a door that opens to the heater box. If it is broken and will not allow that door to open, you will not get any heat anywhere. Please NOTE that these doors are vacuum activated. It could be a vacuum hose with a leak!! All the other doors may be working fine, and from what you say, they are.
  I think that is about all I can think of. I hope I have given you some direction to resolve your problem. As you can see, there could be quite a few possibilities for your delema.
  Again, sorry to take so long to respond but I had to help the Dr. with his Mercedes payment. Please remember I'm a Parts Specialist, NOT a mechanic but I hope this helps.
  Skip
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