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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Buick Technician
Category: Buick
Satisfied Customers: 29523
Experience:  GM Grand Master Technician 2007. 11 years experience.
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2003 Buick Century: heater..cold air..ok goes back to cold

Resolved Question:

Our 2003 Buick Century heater is not blowing out hot air (just cold air). The sliders work ok sliding from blue (cold) to red (hot).
It will SOMETIMES blow out hot air when the car is moving, but once it stops, it goes back to cold.
Need to get this fixed so we can defrost it in the driveway in the winter!
Submitted: 6 years ago.
Category: Buick
Expert:  GM Tech (Cam) replied 6 years ago.

Hi, I'm Cam. May I ask your first name?
I am working to get you a fast accurate answer. About your vehicle, Does ite go full cold or just cool to warm?


Customer: replied 6 years ago.


Full cold. As if you had the a/c on. Even when the temperature sliders are all the way to hot. Moving the sliders up/down does nothing, temp stays cold.

IF it blows out heat when the car is moving it's only warm, not as hot as it usually is.

Expert:  GM Tech (Cam) replied 6 years ago.

Sally, is the check engine light on?


Customer: replied 6 years ago.

The "Service Engine Soon" light is on.

Expert:  GM Tech (Cam) replied 6 years ago.
Ok, We will need to get the codes from the system to start and have an good idea of which direction to go. Most part stores will scan for free.
Customer: replied 6 years ago.
Relist: Answer quality.
I would have brought it into a shop for a "scan it" answer. Wanted something more concrete.
Expert:  GM Tech (Cam) replied 6 years ago.

Sally, I am suggesting a FREE scan. I can't see your car so I am asking you to get it scanned FREE. I suspect the code will be a P0128 and that it needs a new thermostat, but I don't want to say GO SPEND MONEY until I am sure and we look at everything FREE or as CHEAP AS POSSIBLE first. Please work with me here.


Customer: replied 6 years ago.


What do they need to scan exactly? So I can tell them what to do and see if they will do it for free

Expert:  GM Tech (Cam) replied 6 years ago.

Most part stores, go in and tell them your check engine light is on and can they scan it.

Record the code number and reply back here then.


Customer: replied 6 years ago.
ok a local parts store does have the scanner I can use. They said I'll need to know which plug to connect it to? Do you know where the plug would be?
Expert:  GM Tech (Cam) replied 6 years ago.

It is under the dash, left side around your knee or shin.


Customer: replied 6 years ago.

Code P0128

But the service guy didn't think that would relate to lack of hot air blowing out? he thought I would have seen a dip in my temp gauge on the dashboard (which I haven't, it's been running in the normal range as usual).

Can a P0128 code effect the heat?

Expert:  GM Tech (Cam) replied 6 years ago.

This code is almost always set because of the thermostat opening too early. The computer sees the engine has not reached a set temp in a set time and assumes there is an issue. The code is actually for the coolant temp sensor, but I have yet to see this code set because of the sensor. Replace the thermostat and see. It is not an expensive part.

Customer: replied 6 years ago.

Would the broken thermostat keep the blowers from blowing out hot air?

Not trying to be obtuse, but to see the connection.


Expert:  GM Tech (Cam) replied 6 years ago.

Yes, the engine will not get to full operating temp so it will not force the water through the thermostat. Start with the thermostat as it is the cheapest place next to go and I have a good feeling it will fix this.


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