QuestionMy wifes Liberty started having a/c problems several weeks ago. A/C would work fine, soon after engine start up, but after several miles, we lose AC, and get warm air. Intermittently while driving at highway speeds (60+) A/C would work for a short time, then again blow warm air. A mechanic suggested replacing the Radiator Fan Module, as only one speed of the fan was working. Freon level was fine, with no signs of leaks. Does the fan module sound feasible as to the cause of the loss of AC? Thank You!
AnswerHi Daryl,
Well, not really. In most cars, when vehicle speed reaches above 35mph (that varies), most electric fans are shut off, since the motion of the car should provide adequate airflow across the condenser. Regardless, the electric cooling fan in the Liberty is single speed (unless this an export model) -- so if you've got one speed, that should suffice. At 60+mph, that shouldn't matter anyways. Suggestions are great, but I would advise against replacing any component without proper diagnosis -- and in this situation it doesn't really make sense.
If it were at idle, I'd say it's a good possibility, but at highway speed, it gets tricky. It shouldn't be an obstruction, like flat condenser/radiator cooling fins, or leaves, plastic bags, or anything else that can get lodged in there, but check anyways. Also, the basic refrigeration system seems to be intact, so that can be somewhat ruled out (unless the evaporator is freezing up). The nature of it being intermittent kind of rules that out. It also makes tracking stuff down like this... challenging.
The absolute best tool to diagnose with is the DRB3 (or any decent scantool), so you can monitor things like A/C request, A/C Pressure switch states, A/C Compressor Clutch apply, or any other parameter -- while driving. Then, if it happens, you can see a better picture of where to continue looking. Often times, flaky problems like this are exhibited by electronic components. A/C Control heads have been known to cause blend doors to intermittently travel to full stop before. Not likely, here.
Back to the Evaporator freeze up thing I mentioned, particularly since it's most prone in this situation. The A/C system should pump out the absolute coldest at highway speed -- sometimes, unless the system is cycled, the evaporator (in the passenger compartment, below the right side of the dash) can literally freeze up. Ultimately, the PCM (Powertrain Control Module) controls cycling through the compressor clutch relay, and earlier models had issues with this. Then, the manufacturers starting putting A/C Pressure Transducers in, and THEY were an issue, since they signaled the PCM when to cycle. In addition, you might want to make sure the Compressor control relay, in the PDC under the hood, is not stuck on (you can swap it with another that has the same part number). Here's a quick test -- if it happens, reach under and feel the bottom of the A/C case -- if it's very cold, then this is a possibility. Check to make sure the evaporator is draining properly as well, because if the drain is clogged, it can fill up the bottom of the case, and create an iceberg in there(!).
Aside from that, you still might benefit from a complete diagnostic (from someone that knows these things intimately), since intermittents take an experienced eye to catch. Good luck!
