Aloha 89 TR. AC hasn't be charged for several years but worked well before.. Pulled 30 inches of vacuum and it held for hours. Put in 2.86lbs of R12 but the compressor never kicks on. It's holding get all the freon but it doesn't run. Ideas? Thanks Scott
fuse? pressure switch? have a look if power will go the the compressor. for short time you also can put directly 12 V to the compressor and hear if the clutch will click
Checked fuses and relays. Pressure switch is on recover dryer right? There's on wire on the compressor. 12V there?
I think so, but not sure right, one wire, but not always plus on, only when the compressor has to work
OK,a temporary 12V to the compressor runs it. I now have cold air. How many things have to be in sync before the compressor will run? Pressure switch, thermostat,.....and how to test each.
you may jump the pressure switch or just check if this switch is "on". this has nothing to do if the AC is switched on or off.
Not directly related to your problem - The cabin blower was blowing weak. I found a voltage drop at the switch on Hi. I bypassed the switch, and the fan blows very strong. I'd say rivals any other auto fan I've felt. I was thinking about setting up a relay (like the "slo-window fix"). I did not change anything, and live with it. Just throwing this out there wondering if anyone has done this / something similar? Apologies to hijack thread. I had something similar where I knew system was charged, but could tell compressor wasn't turning. I cycled switch many times, and didn't hear relay click. Out of frustration, I cycled ~20X more, and it clicked and started working. I guess I'd suspect relay is flaky, or possibly control voltage going into relay is problem. I think relay gets its input voltage through fan switch too? How we love them so!
Be patient and start with diagram in owners manual. It's one of those circuits that's a grind to study! It goes battery to fuse-box --- but then it becomes a bunch of elements which interrupt the circuit. Relays & switches. Here's the approach (it was successful) that a mechanic buddy shared when I was on a PhD schematic hunt. First question is - When did it last work? and what if any changes were made to this system? You did Freon, so you could have exposed a pressure limit switch issue. I'd check that switch. Then if switch doesn't check out, I'd suggest manifold gauges to verify pressure. Also, can someone verify if the TR has an OVER pressure switch? If TXV (Thermostatic Expansion Valve) has a problem, pressure can go too high etc, and some systems have a protection switch for this. I just had a thought!! If compressor wasn't turning, how did you fill/charge system? If you have Freon liquid upstream of TXV, compressor could push liquid, and open that over pressure safety switch. In this case, you don't want to run compressor! I believe this will mediate itself over time as freon sees some temp variation and expands / condenses about system. How much time? I'd guess a few days?? Ordinarily these components don't just fail unless system was open and left open for extended periods with high humidity. News flash - Check your over pressure switch. I just noticed in the Ferrari TR WSM Section I33 item# "82 Freon max. pressure switch A.C. system" I don't know where exactly on a TR that is, but I'd start checking about the TXV. If over-press switch is triggered, then check with manifold gauges, and see if it is self resolving over time. Hope this helps. Can some smart Ferrari HVAC guru concur, or tell me the holes in my theory.
Just re-read initial post. Sorry for thinking out-loud #1 Good vacuum & system tight #2 Put in prescribed Freon (must have taken time w/o comp running) Now compressor won't go -?-?-? New strategy. Start w simple stuff. Check fuses, then check relays. Maybe swap a relay from another circuit as a test. Make sure it's the same type. fingers crossed for you.
With everything plugged in, engine running and AC "on" at full cold, measure the voltage between the CN (orange-black) wire at the high-low pressure switch on the Dryer and ground: Should be +12V -- if not, the AC ECU is not trying to turn on the compressor (either its bad itself or a sensor to it is bad). If it is +12V, then measure the voltage between the VM (green-brown) wire and ground: That, too, should be +12V (when the CN wire is at +12V). If not = high-low pressure switch not working or the refrigerant pressure is out of bounds. If it is +12V. but the AC compressor does not engage = wiring or connection problem from high-low pressure switch to compressor. You need to know what is, or isn't, happening on the CN and VM wires at the high-low pressure switch to know where to look next.
I can always depend on you Steve. Thanks. Will check and report. Sent from my SM-N920V using Tapatalk
Im stupid. Therefore, I would check the cockpit switch to ensure contact is made. After seeing first hand the amount of gunk amassed via the grease turned glue inside the window switches....I wouldn't rule out the AC switch. Sorry for the run-on sentence.
Steve, I have 12v in and out of the pressure switch. So what sensors could it be? Sent from my SM-N920V using Tapatalk
None -- if the VM wire at the high-low pressure switch is at +12V, the AC system is (correctly) trying to engage the compressor. You need to check/unplug/reseat the connectors in the path of the VM wire as it goes from the high-low pressure switch to the compressor EM clutch: the VM wire in the "a" white connector on the fuse-relay panel, the VM wire in the "j" white connector on the fuse-relay panel, and the VM wire in the "C11" connector under the coolant expansion tank. If just unplugging and reseating those three connectors doesn't get things working (or if there isn't something obvious like a broken wire), then you've got to measure the voltages on those VM wires relative to ground (with everything plugged in and trying to run the AC compressor) to see where in that food chain the +12V goes away.
Thank you Steve. I'm sure I'll find it now. Considering the locations of where you indicate there is a junction, I'm sure it's one of those. I hate those locations! Too many problems. And yes I already know about the gold connector kit. Sent from my SM-N920V using Tapatalk
As always, Steve M makes it easy for me. Thank you sir. It was those little fragile bendable fingers on the wire ends of the harness plugged into the fuse panel. I saw a thread on here a while back about replacing all of those with some modern non-insulated push on terminals. I just keep replacing all the expensive easily failing F stuff with generic dependable stuff. Original?? LOL!!! Original SUCKS! Anyway, I was getting voltage on 1 wire but not on the other when probing those 2 at the fuse panel. So, I pulled the fuse panel out and the back cover off thinking one of my custom circuits had failed. I "custom rebuilt" this sucker about 12 years ago. It's not pretty (nobody sees it) but it has worked flawlessly. Still, I tested my connection for the circuit in question and it was fine. If you look at the pic below, it's the lone wire in the bottom right corner and it only feeds the voltage from one harness connector to the other, there's nothing else involved. Those stupid little fingers on those wire connectors that spread so easily, that was it. Remove, close gap, replace, all is well...till they spread again. I gotta replace those. Ahhhhh, it's snowing inside my Maui TR again.... Image Unavailable, Please Login
Glad that you got it sorted Scott. Yes, those two-prong female terminals weren't the greatest design choice, but usually it's the things drawing higher current that give them trouble (as that heats them up more). Yours is a first report here AFAIK of the AC EM clutch circuit being affected by them -- lucky you
Thanks, it's pretty in an ugly sort or way. And yes, it works well. Nice thing is if it breaks its easy to fix.
