Quick question for the 308 AC experts over here... When I turn on the AC on my car, the clutch of the AC compressor does not engage. I have checked the power going to the compressor clutch and realized that I have no power at all. I note however that the right motor fan (the one dedicated to the AC) goes on so it means that if there is something wrong, it is between the AC relay and the AC compressor. I also note that, between the AC relay and AC compressor, there are two pressure switches which roles are to stop the Compressor in case the pressure in the system is too low or too high. In my case, It's probably been more than two years since the last recharge of the system, so here are my questions: 1. Is it possible that the pressure in the system (since the last charge) dropped so low that the low AC pressure switch prevent the compressor from turning on? 2. Where is located this low AC pressure switch on the car? I have found the high AC pressure switch (#107213 or 16. on the exploded view: https://www.eurospares.co.uk/parts/ferrari/308-quattrovalvole-1985/cooling-heating/air-conditioning-system-38812) but can't find the low one Before recharging the AC system, or investigating any leak in the system, as the case maybe, I would like to make sure that these switches are working properly. Thanks in advance
1. Yes. 2. The pressure switch on the dryer is the only one I'm familiar with. If you put a jumper wire on the connector, you'll hear the compressor clutch 'click' if the clutch is functional. If you hear the click, then system pressure is your next place to correct.
From my limited experience: 1. Yes, and is likely. Have a jumper wire to bypass the switch to turn the compressor on. 2. In my car, '88 328 there is only one switch that has a high and low2 pressure cutoff function.
Thank you both. This is very helpful. Next step now: I will bypass the switch as you suggest and check whether my compressor clutch is functional.
Find a 12v source. Battery is pretty far away but a good source, run a wire from the Pos side and briefly touch it to the compressor wire, you will hear a clank.
Here is a pic of the switch and the NAPA box for the part number. Image Unavailable, Please Login Image Unavailable, Please Login
When replacing the switch, check the threads. The original Ferrari switch had a thread M10x1. At least on the 308 applications. The widely available replacement switches have an 3/8"-24UNF-thread. They are close and one can screw the parts together, but I would not rely on a connection with an UNF-male into a metric female thread. I went through this recently and made an adaptor. Image Unavailable, Please Login Image Unavailable, Please Login Best from Germany Martin
This is a normale binary pressure switch with standard threads $32 USD. https://www.napaonline.com/en/p/TEM207792 You can use any but pressure choice must be correct one for chemical refrigerant you use. If you use R12 switch for R-134a then the pressure cutoff too early and R-134a misses optimal pressure because R-134a must operate higher pressure
Before I messed with it I would check the A/C pressure. If its too low the compressor won't engage. I think the normal pressure with the engine off is 125 to 150 psi. If you change the pressure switch you will probably have to recharge it anyway. I changed mine to r134 a while ago but didn't realize it needed a different pressure switch. Guess that's next on my list.
BTW my 78 GTS A/C is all original with the exception of the drier and O rings and with R134 it has held pressure for 2 years.
' Switch high pressure cutoff is only 1 bar difference so not super important as AC still runs OK, just not super optimum
Yup. My AC works pretty well. One of my projects is to change the cabin fan to the higher capacity SPAL unit and since I will have to recharge it anyways I will change to the higher pressure switch.