It's the middle of winter, you're in your Cadillac Seville and your heater isn't working. This is one of the worst situations a driver can be in. Even after pushing all the buttons and turning all the knobs of the A/C heater control, it just doesn't seem to work. Here's quick guide to help you diagnose Cadillac Seville A/C Heater Control problems.
A number of problems may cause this to happen. The first two causes and the simplest ones to fix are either a blown fuse or a malfunctioning relay. A simple swap of these components is all it will take to handle the problem. Another problem is a stuck thermostat that is tricky to fix but relatively easier to replace. Blockage in the cut-off valve of the vacuum actuated heater may prevent engine heated water from getting into the passenger compartment, where it transfers its heat.
This problem usually occurs because of a problem in the Cadillac Seville's electrical system. If you're lucky, a blown fuse is the only thing you have to worry about. Worse, the control module of the heater has died and will need to be replaced. Worst, you may have a damaged wire somewhere along the airconditioning and the heater control system. Looking for the damaged wire will be a time-consuming process.
One very likely cause of this problem is a bad blower motor. Blower motors usually last a long time and don't need regular maintenance, but that still won't stop them from suddenly dying one day. Another cause is a bad motor relay, and as usual, a quick replacement will have the air rushing out of the vents in no time.
This problem is caused by one of many things. Firstly, there is a chance that the heater control itself is malfunctioning, a likely occurrence if it is already old or has been battered. If you've just replaced the control, you've either been given a lemon or you may have another problem. Second problem is a malfunctioning temperature sensor, also a product of aging and wearing out. Replace the part as usual. Lastly, you may have a bad air door control motor. It is possible to fix this component. If you've no success in doing so, replace as always.