Howdy, Last year when I took my '89 328 in to the dealer and had the belts done, I had them check my AC system, since they were going to take off the AC compressor anyway. They said the system was fine, but had electrical issues, including the fan switch and the thermostat. I have replaced the fan switch, so that is all good, but I am now thinking of replacing the thermostat. While I was replacing the fan switch, I looked at the thermostat and it looks easy enough, but the tube that runs from the switch is what makes me wonder what I am getting myself into. Then I thought, maybe there is a issue where the tube connects on the other end? The previous owner said that after he had the 30k service done at a Ferrari dealership, the ac worked fine, and then stopped. So, I just thought it had a leak..... So, maybe some of you know the answers? How hard is it to replace the thermostat and "tube"? Are these things known to break? Where does the other end go, and do they become "disconnected"? Is this a Ferrari only part? Any advice would be greatly appreciated.... Not that I really need the AC, but not having something work on my car makes me nuts..... Actually, the dealer gave me a fairly decent estimate to fix it, but I like to fix things myself if they are easy enough, but I like to know what I am getting my self into before I make a decision. Thanks in advance.... Bob
Yes! If the tube breaks, the stuff inside (I think ammonia) leaks out making the thermostat inoperative. It should be placed near the outlet tube of the evaporator unit. It senses the temperature and transmits a signal to the thermostat which then turns the A/C compressor clutch on/off (to regulate the desired temperature). I'm not sure about the parts situation for a 328. I know I had an extremely difficult time trying to get a thermostat for my GT4 - I ended up adapting one from a Maserati. If they're quoting you a decent price, make sure they have the parts in stock.
I've come to question what that capillary tube does. I broke mine accidentally when changing to new heater bezels and cables. The expansion valve has a similar capillary tube ending at the evaporator acting as a throttle to regulate adequate refridgerant flow through the evaporator while preventing too much to icing it up. The temp switch capillary tube on the other hand, (my current theory) is designed to cycle the a/c compressor clutch to regulate cabin temperature. Why else would it be labeled 'Temp'? As such, I'm coming to wonder if this capillary tube is only just to monitor cabin temperature, not evaporator temperature freeze point. My temp switch capillary went forward in the center console so I assumed it went into the a/c evap but someone else will have to eyeball this to verify. I.e. does anyone have their spare tire shroud off to know if the capillary tube does extend up from the cabin, through the grommeted hole, into the evaporator area. The 3x8 a/c unfortunately will ice up the evaporator before the cabin gets cool so most of us simply keep the temp switch at max. If the a/c had greater power, the cabin temp would be kept at a constant comfortable temperature and that temp control be of value. For now, I've simply wired it closed. Until I can find a replacement anyway.
The capillary tube runs under the center console, behind the dash, and through the firewall, into the air flow in the evaporator. It's quite a job to replace. (The routing is needed by the capillary tube, which won't work right if the "bulb" (sic) end is positioned pointing upwards. So it loops over the evaporator and hangs down into it.) It measures the temperature of the air moving through the evaporator. Temperature changes at the evaporator will cause a pressure change in the capillary tube ammonia, which then operates a diaphragm inside the switch to open or close the contacts which control the compressor clutch. In a 328, it's the thermostat that prevents the evaporator from icing up. With the engine off and the ignition on, turn the air control on, and then rotate the thermostat. If you can hear the compressor relay click, the circuits are working. If not, you have to check the refrigerant pressure switches as well as the thermostat. You can by-pass the thermostat switch with a 5A blade type fuse to check if the relay will click, to see if the problem is the thermostat. If it doesn't click with either the thermostat or the 5A fuse, you have to check the pressure switches and/or system pressure. (That, or you're testing the aircon in air temps below 32F. ) I played around with building an op-amp circuit to replace the switch, using a thermistor at the evaporator, since I could put connectors in wiring to the remote thermistor. (The capillary tube is one continuous tube.) I even built one on a home etched circuit board that was small enough to fit where the stock switch sits. But the unexpectedly large coil current of the Bosch aircon relay was more than the circuit could handle. I never did get around to finishing the MkII version (with a small relay to operate the bigger relay), as things got busy at work. Image Unavailable, Please Login As a stopgap, I had a 5A fuse in place of the thermostat, and a radio shack indoor/outdoor thermometer sitting on the console with the "outdoor" probe extended into the vents. The air does blow cold. There's just not much volume of air moved. If the evaporator ices up, the amount of air moved becomes even less. So the thermostat mostly keeps the evaporator just above freezing, so the humidity in the air doesn't turn to ice to block airflow in the evaporator unit. Switching the system manually with the fan switch isn't as efficient, as the warm air flow will "thaw" the evaporator faster than turning the fans off. After doing the "manual" thermostat while the op-amp project was on hold, I finally just had the dealer replace the stock thermostat. The replacement part from a Ferrari dealer (a couple of years ago) was over $400. Plus installation labor. The one that was in the car was labeled "GE" and "3ART5". http://www.geindustrial.com/cwc/Dispatcher?REQUEST=PRODUCTS&pnlid=4&id=3art5t The GE part can be ordered from refrigeration supply companies. It's from a Coke machine.
