QuestionI have a 1999 Grand Cherokee Limited with the AZC dual zone infrared sensors. My air conditioning works perfectly in the morning and any time it has been garaged during the day (probably temperatures in the 60s or 70s)... nice, cold, strong-blowing air. However, if the Jeep has been sitting out in the heat (probably temperatures in the upper 70s and 80s) ), the air won't blow at all -- even if the vehicle hasn't been in operation. If I override the automatic controls, I don't get air(hot or cold) passing through the vents. I used the AZC diagnostic mode and didn't receive any fault codes. I have had three reputable (supposedly) shops take a look at it, including the dealership, and I have received different answers to the problem from each shop -- blower motor from one, thermostat from another, and the AZC control unit from the other. Of course when I ask each about what the other shop advises, they all say it could be any of them and it's just a trial and error. I just can't accept that answer... Any thoughts??? Have you heard of this before? What's the deal!?!?! It's approaching the 90s, and I need some A/C!!! Thanks!
AnswerHi Justin,
According to your description, you (periodically) have *no* airflow, regardless of the speed setting on the Control Head? If so, here's what I would check first -- look under the passenger side of the dash for the blower motor. Right near it is the connector for the Blower Control Module. Give that thing a nice wiggle, while the system is on. If you get airflow, then you most likely have a faulty module. However, it doesn't end there -- if you disconnect the connector, and look at the terminal end, chances are it will be melted (sometimes, you can't even disconnect it!). Looking more closely, particularly at the fat red wire, it might look discolored due to heat. If you pop the Control Module out, you might see the inside is melted as well. This is a common problem on these systems, and the fix is to replace the module *and* the wire harness to the module. Here's the rub: it's a short harness, but the HVAC case has to come out. For a while, technicians could get a harness 'pigtail', to solder onto the old harness, but I'm not sure they are still available. If not, most techs will cut the end off the new harness (with plenty of wire length), and solder (crimp for the lazy ones) it onto the old harness. Replace the module, and you're in business.
I've read your description two or three times, if only because I want to understand this issue. My biggest problem is that nobody suggested this fix... particularly the dealer. THEY should know this issue inside-out. Either I misunderstood your concern, or those shops are questionable.
There were problems with the A/C Control Head, but those were mainly Blend control issues -- for example, the airflow would gradually get warmer as the system ran. The fix for this was a new ATC Assembly (Control Head). Other than that, they would require a calibration every now and then (using the DRBIII scantool), but that was for similar temperature issues.
The worst problem with these systems is the blend door breaking in the HVAC case (well, the evaporators leaked as well), but this was not intermittent, or dependent on whether or not the vehicle sat in hot or cold weather. It might partially break, but in a dualzone system, that would only cause issues on the driver OR passenger sides. It doesn't seem to resemble what you are experiencing. I think what I originally outlined will work for you.
What ever the case, good luck!
