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2003 Buick Century 3.1 L

I have a 2003 Buick Century 3.1 L with air. My difficulty is I cannot get heat. I cannot generate warm air to the windows, floor, bilevel. Heat will not come on if I turn on the air conditioner. The temperature slide switches offer cold and colder. There is no function switch from outside/inside recirculated interior air. Fluid levels are full and operating temperatures go to normal. There are no leaks. Do you have any thoughts? Thank you!

Since this probably has an idiot light rather than a temp gage, I’m wondering of the engine is not getting to running temp. Without a gage you’d have no way of knowing, this would not trip a CEL, and you’d have no heat.

If my guess is right, the fix is a very inexpensive thermostat replacement.

Mo9untain may well be right. I would add the possibility that the heater controls are at fault. Some use vacuum to work and I believe yours is one. A leak in the vacuum system anywhere can cause that problem. Good Luck

Beginning with the simplest/cost effective steps…

  1. THERMOSTAT BAD: Check thermostat (set in hot water and bring to boil checking temp when it opens) It should open near the temp stamped on the metal ring. If not, replace ($6).

  2. WATER PUMP FAILURE: Check for small leaks from your water pump. Water slowly leaking out of a hole located on the side of your water pump means its busted and it wont feed hot fluid through your heater core like it needs in order to produce hot air.

  3. HEATER CORE CLOGGED: Disconnect both heater hoses leading to heater core (usually hidden behind firewall). Disconnect them only on the engine head connection and water pump connection. Using water pressure from a nozzled garden hose, “blow-back” through each entryway into the heater core.

  4. VACUUM HOSES DISCONNECTED: Check for any vacuum hoses disconnected under the hood. Then you will have to remove dashboard front panel and air control assembly to see if there are disconnected, broken or crimped vacuum hoses leading to it under the dash area. These are usually brightly colored hoses. On older vehicles you will hear a slight “HISS” when switching from Cold to Heat Modes to help you know its working.

If you try all these things in order I would be surprised if you didnt find the problem.

This Buick has a temperature gage. We have the same year and body style.
My guess is the thermostat. I might suggest a good flushing and replacing anti freeze with some good green stuff. (prestone or zerex) I am not fond of DEXCOOL if you have that red/pink/brown looking stuff in there.