Having trouble with my heat in my 2002 Buick Lesabre Limited

delila65

Can someone please help me, I am having problems with the heater in my 2002 Buick d Lesabre Limited. When I first turn my heat on it warms up fine, then when I get 10 to 15 miles down the road it starts blowing out cold air, I have to turn it all the way up to 90 degrees then it starts blowing hot air again. If I try to adjust the temperature down it will blow cold air again. I replaced the air door actuator and it still does the same thing. Does anyone have any idea what my problem might be. Thanks.

imidazol97

If it's a Limited I has dual temperature controls. Right? Did you verify that both temperature regulating actuators are moving when the temp is raised up or down on the requested setting--with the engine hot and car warmed up?

There are several things in play here: if dual controls, are both sides having the same problem?

Is your cooling system FULL. Not the reservoir but the radiator itself. This needs to be checked at the radiator cap with a cooling system cooled down for .5 to 1.0 hours. Open cap carefully. It might have air in it.

The system may have an internal seep that loses coolant and the suction disk on the radiator cap may not be working right letting the system suck coolant from the reservoir back into the radiator as the coolant in system shrinks as it cools down. Clean the radiator cap with a toothbrush and Dawn dish detergent in the center where there's a small disk. I've seen them badly cruded up. I'm not sure that might be your problem but I'm offering ideas.

Is the exterior temperature indicated on the heater readout in the correct range? The HVAC system uses feedback temp sensors in the car to determine what the inside temp is for adjusting the heat output. The suction area on yours is a set of holes like a salt shaker size on the plastic on the right of the driver steering column. Air taken in there is used to help the HVAC computer determine how to adjust the blend doors based on the requested temp setting(s) and the exterior temp. I believe there's a tube to that air intake grid. Has someone messed under the dash and possibly disconnected that? It might be getting return air from the heater output and thinking it has warmed the car up so it moderates the heat output.

Buick had one of the best systems for the HVAC automatic controls especially the dual system in my opinion on the leSabres and Park AVenues.

imidazol97

IF your car has the dual temperature controls..., this, I believe, is the driver side location of the electric actuator. With the engine running and the plastic cover off under the dash on the driver side you should be able to locate these actuators. They usually have a white part that's movable so you can have someone adjust the temp request with the car all warm and you should see the blend door actuator change to accomodate the request.

Yours may be slipping which happened on some of the earlier leSabre series. The motor turns but the part moving the door inside is slipping on the hub, usually due to the plastic splitting with age and not being tight.

The modules are fairly easily replaceable by someone who's careful and thin and agile to work upside down under the dash lying on the floor.

Note the blend door changes the temp. The mode actuator changes the direction of the air flow for defrost, dash, floor modes. There is another blend control on the right side of the HVAC box for the passenger side control.

If replacing yourself, be very careful buying replacement because the terminology used by aftermarket folks for which one is which is very poorly done.

imidazol97

Another test that might be interesting is to cover the sun sensor on the top of the dash in the middle so the unit does not think it's getting heat from direct sunlight. I know the computer is supposed to also use input from that to decide how to adjust the settings along with the requested temperature and the feedback temperature from the air intake by driver's right knee.

delila65

Thanks for your recommendations @imidazol97 I am going to test the new actuator that I installed on it last week to see if I got a faulty one. I know sometimes you can get bad ones. I do not have dual temperature controls on my car. I am hoping it is the actuator that is bad. I will let you know. Thanks again.

imidazol97

thecardoc3

delila65 said:

Thanks for your recommendations @imidazol97 I am going to test the new actuator that I installed on it last week to see if I got a faulty one. I know sometimes you can get bad ones. I do not have dual temperature controls on my car. I am hoping it is the actuator that is bad. I will let you know. Thanks again.

@imidazol97 Has done a pretty good job of trying to give you some direction. Based on how I am interpreting your description if you put the system on max heat, you get heat. Right? But if you move the control away from that setting you lose your heat. If that is correct, it cannot be the blend door actuator.

That leads to the next question. How exactly were you planning on testing it?

Even "manual" AC HVAC controls today are heavily electronic in nature and are often tested the same as fully automatic systems, which means yo need a scan tool that fully supports the system is required. Today some professional level tools would likely be sufficient but back in the 2000's a technician had to have the GM Tech II scan tool in order to see command and position data, input data such as in cabin and ambient temperature, and bi-directional controls.