[NickD]

If you park your vehicle with a soaking wet evaporator in particular in a warm climate climate, nature will take over for developing mold. Not a new problem, started way back in the 50's when AC first became popular. Was a 1939 Packard as the very first vehicle that had AC.

Only way to prevent this is to switch the compressor off, my rule is about five minutes to leave the blower motor run at full blast before parking your vehicle. And have been doing this in the early 60's without any mold problems.

But mold problems is just the start of your problems, will also have corrosion problems. $$$$$ is the only result of these.

When automatic climate control first came out in around the early 60's, did not have a so called "Econ" mode, all it would do is switch off the compressor. So on these, mounted a rocker switch under the lower dash in series with the compressor clutch solenoid so I could switch it off. Didn't have to do with when they finally added on the Econ switch.

GM is very well aware of this problem, on just a hand full of vehicles, added a timer to keep the blower motor running for about five minutes after the ignition was switched off.

What is really downright stupid is switching on the AC with Defrost, at these colder temperatures, the moisture is very low, and switching on the compressor with a very cold compressor seal that is stiff, so you would lose refrigerant. Idiots that designed the Cruze did this exact same thing, even though they added a compressor switch. You can see that green light come on, but only when the ambient temperature is above about 34*F.

Not quite as bad with the V-5 compressor as it runs all the time, but when the cycling system was used, another POS, compressor would cycle on and off continuously accelerating from zero to the engine speed putting huge unnecessary stress on the belt drive system wearing it out with very little affect on defrosting your windshield.

On previous vehicles using a real mode switch, could cut the wire off that runs the compressor, but can't do this on the Cruze without having the source code on the BCM. So I just crack open a window the defrost the windshield almost instantly. Below 34*F, no problem, a thermistor keeps the compressor off.

Yet another problem finally solved with the Cruze is adding a cabin filter. Would describe the squirrel cage blower wheel as a leaf chopper that would pile up debris on the face of the evaporator and plug the drain hose. In these cases, the evaporator is sitting in a pool of water. Normally just removing the blower motor would give access to the evaporator so you could clean it out.

Slightly off topic, but can have the same exact problem with the HVAC system in your home, when the AC kicks off, so does the blower leaving the evaporator soaking wet for mold buildup. Solved this by modifying the furnace so the blower is always running at a low speed. Not only prevents mold buildup on the evaporator, but the entire house as well. Did this back in 1965 with my first HVAC system installation. With my newest furnace, low speed was running too high, so designed a motor control circuit to slow it down. Also keeps your home with a much fresher odor.

This is what is called common sense, that is becoming rare nowadays. And since that motor is always running, its the start up that really wears them out. Still kept my 30 year old blower motor, and still runs and looks like new.

 

[NickD]

Ha, never switch on the AC when driving in town, won't kill me, and just wearing it out. Should I get a portable AC unit I can strap to my back when walking out to the mail box, cutting my grass, walking my dog, or biking? Just sitting there in the car and not really doing much of anything with power brakes and steering. Then always a breeze when the car is rolling.

Can recall doing a 25 mile forced march in 98 degree weather with a 65 pound backpack on and a very hot hat and uniform on. Heaven was sitting down under a shade tree, back pack off, and getting a sip of water from my canteen. Its all relative.

Now with my wife and grandkids in the car, that is when the AC gets switched on.

 

[NickD]

R-134a high side pressure drops to about 35 psi at 40*F, completely worthless to switch on that AC with defrost at these temperatures. Besides that PAG oil, women's facial cream is very stiff at these temperatures as is the compressor neoprene seal. All you are doing is wearing the darn thing out, really doesn't remove any moisture.

With other vehicles even mounted a switch in series with that AC compressor clutch coil, didn't do this with the Cruze, just cracked opened the driver's window to prevent fogging the windows, we are the culprits of this.

Was not a problem with Japanese made vehicles, 88 Supra is like this, when that AC switch is off, its off regardless if you hit defrost or not. Not sure about what the thinking is behind switching on the AC with defrost, but at about 34*F and below, R-134a pressure is so low, the thermistor keeps it off. It's that range from about 35 to 65*F is where it automatically switches on in defrost.

Yet another problem that is age old and never solved is debris buildup on the condenser, restricts air flow and high side pressures can of up to around 400 psi! Get very little cooling and really putting one heck of a load on that compressor, water pump is the weak link and the first thing to go in a single drive belt system. Really made life difficult to keep that condenser clean. If you think your windshield is loaded with bugs, look at your condenser.

Another is stone chips, quickly learned on my that little plastic stone shield was missing, dealer didn't believe this, several looked at it, ordered one for me, installed it myself. Front license plate required in my state was actually a blessing, has stone chips in it.

Wasn't much of a problem with tube and fin condensers, one solid piece of copper tubing ran back and forth with R-12, R-134a requires a parallel flow condenser made out of super thin aluminum and is throwaway. R-134a PAG oil is hygroscopic and with moisture forms sludge that can plug up the orifice. Should be completely flushed, deep vacuum drawn, and PAG oil injected in to do the job right. Mineral oil never had this problem.

Yet another problem is that the EPA changed the service ports to a quick coupler from the old reliable Scharder valve, so you could not pour R-12 into these systems, have a tool that let me replace a 50 cent valve without discharging the system, now you have to replace the entire line with a leaking port. Uses a large disc that never seats properly that causes leaks, and while R-12 had a metal cap for the service ports, R-134a switched to plastic.

CFC's were blamed for ozone depletion, but yet 95% of the total CFC production was never used for its intended purpose, all open spraying for spray cans and cleaning, less than 5% was used for refrigeration! And unlike leaded gas that was really a health hazard with a 20 year phase out, CFC's were banned overnight. And the manufacturers of CFC's were not held responsible, but up to the consumer to pay for the conversions.

DuPont came along with R-134a, now being blamed for global warming and while the EPA banned trichloroethylene back in around 1974 as being extremely dangerous, gave DuPont permission to use it for the production of R-134a.

Just a few bit of hard core facts why we are having problems and very expensive ones at that.