[Tomnavigator]

All - DON'T READ THIS IF YOU CAN'T STAND LONG POSTS OR CONTROVERCIAL ISSUES! I am going to explain why I think my a/c issue is in the DDE coding and why fixing the problem with a pulse width modulator is a proper fix. Just before I started having my a/c problems, I had my car apart for over 3 months doing everything I could to make my care more dependable. I replaced and reprogrammed by ABS module. I did a complete brake job. I replaced the transmission fluid and installed an aluminum transmission pan. I replaced the water pump. I replaced the thermostat. I replaced the belts and idler pulleys. I replaced some but not all hoses. I replaced the MAF sensor. I reloaded the DDE programming. I performed a thorough carbon cleaning. I did exhaust system work. I did extensive DEF system work.
A couple of months after I completed all my work (after the weather got hot) I noticed that the a/c was not coming on for about 5 minutes after the car was started. This only occurred the first time I started the car after sitting over night. The second time and there after each day when the car was started, the a/c started right up and worked fine. When the a/c was working it worked just like it should and blew cold air. In Louisiana in the summer your car can get to over 130 degrees and with 100 percent humidity opening the windows does not help much to cool down your car. I checked all the usual a/c issues and could not fix the problem. I posted on the forum asking for help. I did all the things suggested by fellow forum members. Still no fix.
I used a stop watch to see if the timing for the a/c issue was constant. It was close but not the same time each time. I monitored the coolant temperature and it appeared the a/c would come on when the coolant temperature got above 55 degrees celsius. This made me suspicious that the issue was caused by some computer logic since the issue occurred as the car warmed up and only occurred the very first time the car was driven after the car sat overnight.
I ruled out loose connections and wires because they typically don't connect themselves as you drive. Yes, I admit vibration can cause them to intermittantly connect. However, they are not going to always be disconnected after sitting overnight and then connect after a few minutes of driving and stay connected the rest of the day.
I ruled out bad sensors. Most sensors fall into two categories. Analog sensors like oxygen sensors, NOx sensors, MAF sensor, or throttle position sensor that have a variable output. These sensors usually fail gradually and/or by putting put out a weaker signal instead of failing completely all at once. The second type of sensor is a digital (on/off) sensor like a pressure switch, abs sensor, or camshaft position sensor. These sensors usually work or don't work. Neither analog or digital sensors fail by not working for the first five minutes then work fine from then on. However, some analog sensors like an oxygen sensor may be weak and have to get hot before working correctly. The oxygen sensor does not have anything to do with preventing the a/c from coming on to my knowledge.
I have also heard that BMW turns off the a/c any time you accelerate quicker than a certain amount to increase the acceleration and also turn off the a/c any time the battery voltage is below a certain voltage to allow the alternator to charge the battery first.
I just about decided the a/c issue I was having was caused by some weird DDE programming issue when BB_Cuda asked me a question that hit home.
BB_Cuda asked me the question what did you do to the car before the a/c problem started. This made me realize the one issue I had overlooked. I reloaded the DDE programming. This makes sense now. The issue is not sensors. I have the same sensors as before my work, It is not loose wiring or loose connections. Loose connections do not occur fir the first five minutes only. The issue is the DDE programming. The time and effort to reprogram the DDE is not worth the time, effort, and expense for to me. I will reengineer the operation of the a/c. Yes this is not the proper factory designed fix but a workable fix. It is no different than the people who get tired of the emissions related problems they experience with their cars so they install emissions delete tunes to eliminate the emissions equipment. Or the people who add performance tunes to obtain more horse power. These are not factory designed but reengineering of the car to solve a problem because fixing the problem "right" has been determined to be too difficult, not worth the time, and/or not dependable enough. This is why I will fix my a/c issue by reengineering the a/c.

A separate issue is some of the things BMW and other manufacturers do in the name of emission control or fuel mileage.

BMW does some things in the name of fuel mileage or emissions reduction that are not in the best interest of the owners of the cars and I do not agree with. BMW programs some cars to not charge the battery unless the car is coasting. In the USA many drivers never coast. I have a friend that had a BMW 545i. He is a non coaster that drives with his foot on the accelerator or the brake. He coasts for about 0.1 seconds which is the length of time it takes him to put on the brakes after he takes his foot off the accelerator. He always brakes hard which means the time for charging the battery is minimal. Because of his driving style, he replaces the battery in his car every 18 months because his batteries always go dead.
Another BMW programming issue related to fuel mileage is having to register/program the DDE every time you replace the battery. We all lovingly call this registering the battery. Registering the battery is required because the car charges the battery at the lowest minimum level needed to keep the battery charged in the name of fuel mileage. Look at what it cost the average BMW owner to go to a dealership to register the battery every time a battery is changed and all because BMW wanted credit for another 0.1 MPG fuel mileage with the EPA. No other car manufacturer in the world requires a car to be reprogrammed just because you change the battery to one that is higher or lower output or change from a conventional to AGM battery. All BMW owners should be pissed off that BMW does not give a S**t about what BMW is costing their owners unnecessarily for things like requiring battery registration. Who likes throwing away $100 to $300 every time a battery is replaced to have a dealership register the new battery? My 2003 corvette needs a new battery about once every 7 years and costs $300 to replace at a dealership. My BMW needs a new battery about once every 6 years and costs $500 to $600 to replace at the BMW dealer. This is almost twice as expensive as it costs to replace my corvette battery. Does anyone really believe registering the battery of a BMW makes the battery last last twice as long? We do know that registering a battery can double the costs of replacing a battery at some dealers.
I worked 18 years for General Motors with the last 8 years as an engineer at the corvette assembly plant in Bowling Green, KY. I know the efforts car manufactures are willing to go to in the name of emissions controls and fuel mileage. General Motors shipped the corvettes to the dealers with about one gallon of fuel in the tanks and with the windshield washer bottle empty. This was done to reduce the as shipped weight of the corvettes. The EPA fuel mileage of a vehicle is test is done on a dynamometer. The resistance of dynamometer is set using the as shipped weight of the vehicle. The weights of the vehicles fall into weight classes such as 2800 pounds to 3200 pounds. All the vehicles in this weight class are tested using one dynamometer setting. Vehicles from 3201 pounds to 3500 pounds fall into another weight class and use another dynamometer setting. General Motors could get the as shipped weight of the corvette into a lower weight class by shipping the cars without windshield washer fluid and with an almost empty fuel tank. General Motors would then pay the dealership to fill up the fuel tank and windshield washer fluid tank before delivering the car to the customer. General Motors did this even though dealerships charged about 50% more for the fuel and about $30 to add a gallon of windshield washer fluid to the car. All in the name of fuel mileage. At least this was transparent to the customer and the customer never know it was going on.
Other programming thing that BMW does are things like, programming the DDE to turn off the a/c any time you accelerate quicker than a certain amount to increase the acceleration and also turn off the a/c any time the battery voltage is below a certain voltage to allow the alternator to charge the battery to a predetermined level before allowing the a/c to come on.