Cadillac Repair: ignition or computer problem, battery cables, cadillac sts

Question
I have a 1999 Cadillac STS.  I am having several problems with it.  To start, when I put the key in the ignition, sometimes the dash will light up and the car will start and sometimes the dash will not light up and when this happens, the car will not start.  Periodically, the car will just die while I'm driving it and when it dies, the dash lights go out.  What is the problem?  I am also having problems with the ac/heat system.  When in the auto mode, sometimes the heater will not work...it blows cold air even when it is set on 85.  During cold or rainy weather, I can not get the windows to defrost.  What would cause this.  I am also having water leaking problems...could this attribute to the problem.  How do I stop the water leak?

Answer
Hi Shannon,

       Those are some tough questions you have and might be best to have your mechanic look at the car firsthand to test and determine where the problems are.

       If you want to do some checking yourself the first thing to do is if anything was just worked on in the past 2 weeks and then these problems started up go back to that shop and have them recheck their work to see if they left something loose like a ground wire or wire connector.

       The dash lights and starting the car could be a problem with the ignition key theft system or the ignition switch. Scanning the body computor for codes might help. This is something that your mechanic will need to do. A couple places you could check are loose battery cables at the battery and the ground wire on the engine. They used to be located on the engine on the radiator side behind the serpentine belt. For some reason the nut loosens up and then these types of problems happen.

      With the heater problem there could be a problem with the temperature door motor gears starting to strip out. The glovebox would need to be removed and the motor tested to see if the gears are weak or something else is causeing the problem. Since you do get heat I will assume that the antifreeze is at the propper level in the bottle right?

      Water getting into the wrong places can cause the kinds of problems you describe especially since there are alot of computors in your car. To check for where the leak is comming in requires 2 people...one to be inside the car looking for the leak entry point and the second to spray the water. This is how to check. If you know that the passenger floor/carpet is wet then remove the panel below the dash and possably the glovebox. then with all doors and windows closed and someone upside down looking under the dash the other person starts to spray water starting at the base of the windshield by the wipers to see if water comes in. The idea is to spray like it would rain not like you are pressure washing something so gentle is better. After 1 minuit if no leaks are seen then continue to work your way up to the roof paying attention to spray so wayer gets to the side and top molding of the windshield. Sometimes water intrusion is from below the car or through the wheel well/ tire area so if at first you don't find it try other spots. As a final suggestion have someone drive the car into a car wash while you are looking under the dash and maybe that will show the leak. At that point you can determine wheather there is a rubber grommet missing or some sealer needs to be used to stop the leak from outside the car. For example if you put your patch inside the car it still might get in somewhere else or collect somewhere and cause rusting. One other thought is that the evaporator drain for the a/c is plugged and that water is spilling over instead of exiting through a rubber hose in the firewall.

    Hopefully I have been of some help. Bill