360 A/C / Climate Control Question - Electrical?

On my Spider, the a/c compressor does not turn on. I'm wondering if, removing the engine cover (behind the seats) is easier to get at the electrical plug, on the compressor, than from under the car? From underneath, the two a/c lines are in the way to disconnect the plug and limited space for a hand to get up there.
I want to check and see if power is getting to the unit by testing the connection. So far, I've check freon. OK. I've checked the fuse by the battery. OK. and the "stop" button lights when pressed in. So, I'm trying to find the easiest way to get to the plug?
Thanks for any advice.

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Have you checked the compressor relay behind the left hand seat?

Is the blower fan working at different speeds?

 

You should be able to swap it with the reversing relay. Relays shown below.

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I saw your meessage and ran out to the garage to check. I don't have fuses or relay behind the drivers side seat. There's a box that has 3 harnesses going into but only circut boards inside. Would it be in the trunk on a 2001? The only other location I know is where the battery is and that fuse is OK.
Thanks for the responses.


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You have to remove that stepped panel that your tools are sitting on. There will be some relays and fuses hidden behind small plastic covers.

 

Sorry, I misread your message. You said you checked the fuse, but I see you said you only checked the fuses near the battery. There is also a compressor fuse under that panel your tools are resting on. Do you have an owners manual? The compressor fuse should be shown there.

 

Yes, I did a search and found a stick drawing of fue locations and figured, I may have to remove that panel. So far, the fuse under there is OK and will now swap relays. Came back to check, which relay to swap with andd saw your message. Update soon. Thanks for getting back to me so quick.

 

Also check the red fuse (64) next to the brown AC Compressor fuse (65):

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This provides power to the coil of the compressor relay. The red fuse also powers the blower fan speed regulator. That's why I asked you to check the blower speeds.

There may be several reasons why a compressor doesn't run. e.g. If you don't have enough gas pressure in your system, this will be detected by some pressure switches in the forward luggage compartment. These switches enable the relay.

 

So, I put a couple different relays in there and no compressor. I also checked the second fuse you mentioned and it's OK. I've been double checking fuses for continuity. Now that you mention the fan, again. I started to think. I know it works on high and thought the lower speeds were just to quite to hear while driving. Only had the car for a few months. So, tomorrow, I'll check lower speeds. Gas pressure was the first thing I checked. It was in the "safe" zone but I added a little to see if it would kick start it. It's just over the safe zone now but not in the red. Tomorrow, I'll also check for 12V at the fuse locations. Then, back to the compressor connection. I do know, the clutch spins freely but that tells me little.
Thanks again for the responses.

 

A/c compressor will not turn on if the system.is empty of charge. Take it too a shop and have them put the A/C gauges on it. Even better, have them recover the system and record how much refrigerant was pulled out. I'll bet you will find the system.is empty and your compressor is leaking from the front seal.

 

Sorry, I'm confused. I thought the 2 bar and 28 bar pressure switch in the forward luggage compartment sent a signal to the RH Engine ECU to deactivate the compressor relay.

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Perhaps the system has to be almost completely empty before this switch is triggered, not just low.

 

The system will not active if there is less then 1/2 a pound in it. Trust me. Have the system checked for charge weight.

I know you don't want to spend money for a pro to check it who has invested in the proper tools..but sometimes that is what it takes.

 

Sorry Tom, I misread your previous comment. I thought you were disagreeing with me. I see now that you weren't

Maybe I shouldn't have given up caffeine this week.

 

Here's the wiring diagram if you need it. A little hard to follow, but start in the bottom left hand corner at the compressor.

There is a disconnect point just before the wiring goes through the firewall to the engine compartment. i.e. 12H/26H.

https://www.dropbox.com/t/oKHVNCGHLYwUIOBy

Look for the green/black wire. You may be able to backprobe the plug to see if there is voltage there (with the car running). I think if you disconnected the plug completely, too many things wouldn't work.

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Please note that the compressor will not run with button #9 pushed in.
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OK, now I'm a lot confused. I didn't touch the car yesterday, since we took a drive to Sierra foothills for wine tasting. Started again today, with checking voltage to the fuse and relay. Both are good. But now, the pressures you mention (2 and 28 bar), I'm no where near. As tbakowasky mentions, it wont activate with less than 1/2 lbs. The system had somewhere in the 30 to 40 lbs. range when I first checked. I thought, maybe it needs a bit more to trigger the system so I added a little but now my gauge reads in the "alert" zone at 68 lbs. But, far under 28 bar (see conversion photo). So, I'm thinking of bleeding some off. I did talk to my local A/C guy but he doesn't want to touch it.
I do see a green/black wire buried under the fuse box and looks in the correct vicinity of the fuse. But, the fuse does have power going to it so that would suggest, power is going to the compressor, or probably, relay? Am I close?
OK, from all the input I'm getting, I think I can narrow it down to the pressure switches or the compressor is toast. I still want to see if there's 12v going to the compressor at the connector. I may try and raise the car higher so I can get a better angle from beneath.
I will update when I have something. Again, thanks for all the help on this.

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Almost forget. Yes, I did have it out (and in) with same result. Thanks for chiming in....

 

What pressure are you measuring there? Low side or high side? Running or not running?

I’m not sure if that green/black wire you’ve highlighted is before or after the relay. Are those inline connectors behind the driver’s seat not visible or are they lost in a mess of wiring or behind more panelling? If you’ve got power on the green/black wire at the 12H/26H connector, you know you’ve got all the correct signals from switches and computers and there is something wrong downstream of the relay. e.g. open circuit compressor clutch coil.

In theory, you could check the coil resistance by putting an ohmmeter between the relay socket and earth. You could also jumper the relay with the engine/ignition off and you could hear the (faint) click of the clutch engaging. The wiring diagram I posted earlier shows you which relay sockets contacts to check. Let me know if you need further explanation.

 

Just to be clear, Tom was talking about refrigerant weight in lbs, not PSI. Ferrari specify 1.65 pounds (750 grams) for normal operation.

Pressures should really be checked with the engine running with doors closed, max cold, max fan speed for about 10 minutes.
The workshop manual gives the following values at an ambient temperature of 20~22C (around 70F):

EDIT:

around 29 psi on the low side
200 psi on the high side
outlet temperature 46~55F

 

Wow! Great info and the diagram you sent is very well done and easy to read (once I sorted through all the spaghetti). First, I measured the pressure from the low/filling side. And, I had no idea, that weight is measured and not pressure lbs. In regards to the wire, I can assume that if the fuse block has power going to it and the fuse is good, it (12v) should be going through the wire to the next point. So 12H 26H should have 12v.
Tomorrow, I will check continuity at the relay port. I think I can figure out what points from your diagram. I guess I'm looking for either 0.00 ohms or open.
I think, Monday or Tuesday, I may try and convince my A/C guy to just "check the measurements". It does appear, my pressure is to high for Ferrari standards. I've been going to him for years for all my brake and lamp inspections. Well, by tomorrow, I should have enough info on how to move forward.
Thanks, I really appreciate your help.

 

I guess it depends on what you're measuring at the relay. Just be aware that even with the ignition key off, pin 3 has live battery power (12v) on it so don't put your ohmmeter on that. Also, I don't recommend putting your ohmmeter on pin 2. The RH Motronics ECU may not like you putting volts on that (Multimeters output a small voltage in resistance mode). I've drawn a switch symbol inside the ECU for simplicity, but it's probably a transistor or chip.

If you check pin 5 to earth, you should (hopefully) get the resistance of the compressor clutch coil. Sorry, don't have any values for that offhand. Anyway, as long as it's not open, that's a promising sign.

 

According to Google, 3~5 ohms measured at the compressor. So you may want to add an ohm, depending on how good your chassis earth return path is.

 

".................. The system had somewhere in the 30 to 40 lbs. range when I first checked. I thought, maybe it needs a bit more to trigger the system so I added a little but now my gauge reads in the "alert" zone at 68 lbs.............."


While I agree you misunderstood the relationship between the gas pressure and weight in the system you are lucky not to screw up the compressor by adding too much. A lot of people found this out the expensive way, ask me how I know.

For those following along who want to ensure their system is filled I have found that the best piece of equipment is this AC Pro digital gauge system (NO AFFILIATION to AC PRO). Bob at 30 to 40 Psi it would have told you that the system pressure was ok and not to add any freon.


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I'm glad I read your post before I started my "hunt and peck" approach to the relay plug. So, I did measure ohms off of terminal 5 and got 0.00 (photo). I also measured volts off of "3" and got 12v. So, should we assume the a/c compressor coil is shorted? I tried, the other day to listen for a "click" with engine off but ignition on but the fan was to loud. Today, I had my wife sit in the car and push buttons while I was underneath listening. No click.
Unless someone stops me, I'll got to my a/c guy and see if he'll remove the freon and I'll remove the compressor Wednesday. And yes, Fred, you are correct. The more I know about a/c's, the more I misunderstand. I went through a few years of buying wrecked auction cars to repair. They'd sit on the auction yards for quite a while and most had a/c's that didn't work. The first thing I tried was add freon and, they all started working fine. Now, with the Ferrari, I'll let the pros deal with it.
Updates next week and Thanks! Have a great weekend.....

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Bob, do you know if your multimeter has an auto range function? Your photo is a little blurry and I can't make out the button settings. What is that button next to the ohm button? The range display shows kilo ohms. Unless the range is automatically set, I would not assume that the coil is shorted. My multimeter is auto-ranging and shows milliohms when it senses a low resistance.

If the relay is being energised by the Motronics ECU and the coil is shorted, the fuse would blow. At this point, I don't know if your measurements are correct or if the compressor activation logic is being satisfied.