GravityAlwaysWin

Car: 996 C4S.

Problem: A/C works. BUT... Turning on A/C will turn both radiator fans on to low for ~1 second, then to high, staying on high. Even when engine is stone cold. Sometimes they'll turn off after turning off A/C. Recently, they won't turn off until vehicle is turned off. Sometimes there's an audible groan in passenger compartment while A/C is turned on. Haven't figure out if this is the fans pumping up to high speed or something else. This problem started after the car sat for 2.5 months of no use then 2.5 months of engine rebuild. Got it back from rebuild and it's doing this. No reason to believe foul play; the rebuild shop is awesome.

Problem solving attempted:
--Hooked up Durametric. No faults.
--Switched low and high speed relays. No effect.
--Stuck fingers on low speed relays and they _seem_ to click when A/C is turned on. Which would be consistent with the low speed fans coming on for ~1 second, wouldn't it?
--Read every radiator fan thread I could find here and elsewhere for the same problem and couldn't find it. If I overlooked, sorry, please direct me there.
--Replaced ballast resistor on driver side to see if coincidentally both had gone all wonky on me at the same time. No effect.

Diagnostics so far: With A/C off, both radiator fans come on at low speed at exactly the engine/coolant temps listed in shop manual, then go off after a ~5C engine drop. So I know low speed fans work with engine cooling and problem seems isolated to A/C.

Any suggestions for further troublshooting? Available to us are the shop manual, a Durametric, a garage, some tools, friends with tools, and beer to pay friends who come with tools.

Thanks in advance,
Carol

996 4S
'13 Cayenne Diesel
PCA Potomac DE Co-Registrar

ADias

I suggest you post this issue on the 996 forum.

GravityAlwaysWin

Thanks, ADias. Hadn't noticed my mistake. That's what I get for spending too much time reading about radiators and not enough time sleeping.