A/C engages randomly, regardless of switch/slider config
12-27-2014, 07:09 PM
#16
You know, it's very possible that I'm missing the first cycle between turning the key and running back to the engine bay, but I don't hear or feel the characteristic load change. When checking voltage at the evaporator with the engine off and cold, the clutch clicked on so theoretically it should have turned at the first start. The Mrs. is unavailable for garage help (having a car as low as the 928 is a complication for a person recovering from spinal surgery...), so I'll have to see if I can recruit the extended family when they show up for Christmas this weekend.
I was looking for a reason to pick up a set of R12 gauges...
I got 3 semesters of EE under my belt before switching (HA!) over to civil, so I know just enough to get into trouble!
I was looking for a reason to pick up a set of R12 gauges...
I got 3 semesters of EE under my belt before switching (HA!) over to civil, so I know just enough to get into trouble!
Oh well, looks like ya got this issue cornered anyway. Needs a new relay according to your description, then at least ya should be able to turn it off. If it cycles after that, I'd put a meter on the psi switch out by the radiator and see if it has power to ground on the incoming side constantly, and it's cyclic on the outgoing side. I think the clutch coil will be enough load to isolate the switch terminals from ground. That will prove the "psi switch" issue even if ya don't have gauges.
the external HVAC / AC relay thing is easy to do and I feel like a good move if yours is currently failed. And once done, an inline fuse out in the engine bay is a good idea as well.
Oh, while I had the cover off, I cleaned all the slider contacts, checked switches with meter, added LED lighting, and put a dab of black RTV on the slider that hits the max cool (max AC) switch to be sure of positive engagement with a small cushion.
Hopefully once ya get the stuck relay fixed, the rest will be easy.
