Dang! If Ferrari had had access to some PVC pipe, maybe we would have better AC! :)
The quirky thing is still working properly so I cannot check for absent voltage. I took it for a 45 minute drive a little while ago with no problem. The fuse box cover is off as I drive so I can hear the relays activating when it cycles. The weather is quite dry lately but that could be only a coincidence. It will fail again so I'll check the voltages when that happens. Thank you for your assistance in this long term matter.
I live in Texas and used to live in a hot portion of California. I never use the TR A/C at full output.
Understood. This is a common "problem" when chasing an electrical gremlin -- just getting in to make some measurements can wiggle things around enough to change the situation. If it's not broke, you can't fix it, but you'll know where to look if the trouble happens again to try to diagnosis its location better.
I think those vaccum-operated windows were the result of a wager. "Bet you can't..." "Challenge accepted."
Door locks. The 600s had hydraulic windows. Expensive but no noise, very fast and worked perfectly. Our E55 widows are laughably cheap. Junk.
It is possible the bimetallic temperature sensor switch at the condensor fan has failed. The condensor fan would not acivate when it is supposed to, the pressure would quickly build in the system and then overheat and its self protection pressure switch would cut the compressor off. If you drive on the highway, it would work, as the air flow through the condensor would be sufficient, but as you slowed down, the overheat and pressure build would cut it out. The symptom was intermittant cooling and compressor operation, seemingly random as you have described. The condensor fan would randomly go on and off, so appeared to function, but was not responsive to the correct temperatures signals and so was not functioning when it was actually needed. The switch is no longer available. But I was able to get a substitute that has worked for me. Here is the link to my old thread. https://www.ferrarichat.com/forum/threads/ac-condensor-fan-questions.554436/#post-145429902
Thanks for the input moysiuan and I'll keep this available for future reference if necessary. I do not think this applies in my case because the system at times will not engage the clutch WITHOUT the engine having been previously run. Thus it could not possibly be over-pressurized. I drove the vehicle for about an hour this morning with the AC system on full cold. I caught a bunch of lights red but the compressor never cut off. I can tell if the compressor is running because I have a digital thermometer stuck in the duct at the center of the dash. Temperature in the duct rises quickly when compressor cuts off. Fortunately or unfortunately the system is working fine again. Rain and humidity are coming. Maybe that'll get it to act up again enabling me to find the culprit. It has been working properly for the past two days.
95-110F +-5 degrees compared with OEM of 99-108F (converted from centigrade as stamped on the OEM sensor). http://senasys.com/product/2570f110-thermal-switch
After several days of working properly last night it began raining so humidity is high in the garage. After turning the ignition key to run but not to start, the clutch clicked on when I activated the blower switch with the temperature control switch not in the off position. Then I lowered the temperature control switch all the way CCW and the clutch clicked off as it should. Upon turning it back on nothing happened (This is what happens when system quits working.). I picked up my multimeter and was about to check voltages when the clutch clicked back on. Now it is working properly again with both the temperature control and blower switches activating the clutch as they should. I know it is not the clutch because last week during testing, there was no voltage at the high low pressure switch when the system was on the fritz. Grrrrrrrr!
I converted my QV to R134 and a Sandan compressor. I have found that the air produced by this system is cold. I have discovered that indeed there is a problem with airflow. Not the direction of it but rather the lack of it in the cabin. There is no venting for the cold air coming in to displace the warm air in the cabin. Short of putting in some kind of flapper valve to allow air out of the cabin I found that cracking open the windows a hair made all the difference in the world. I recommend trying this simple solution. It will put a smile on your face.
My quirky AC is still working properly. Never found the problem. The AC has never consistently worked for this length of time in years.
Hmmm...must be different on the 308 than the 328. The ac on my 328 recycles interior air through the AC evaporator. The evaporator squirrel cage blower draws air in from the footwell on the passenger side. There is no outside-air connection/intake to the evaporator. Since the AC system doesn't pull in air from the outside, cracking a window on my 328 lets cool air out and allow hot air in.
Excellent point and it may very well be the same on the 308. That being said if it is the cracking of the window is effective in the 308 and the reason may be that the squirrel cages recycle hotter interior air from our terrible heat coming in under the dash and footwell area?
I just had my interior redone and had dynamat installed way under the problem area. I will try not cracking the windows on the first hot day I’m out in the car and see if it’s more like your 328. I’ll report back my findings.