rescue46

Just got my 1st civic si sedan and the ac did not cool, looked under hood and clutch was not kicking in.

1.put cheap gauge on low side had enough psi to come on
2.checked fuses but confusing did not see any marked for ac
3. same thing with relays so I bought one and replaced it hope it was for the ac
4. swapped relays around still no luck
5 jumped pressure sw low side kicked in and back out almost immediately but only once
6. tried the self diagnostic holding the recirculate rear defrost buttons turned key on light came on fan came on diff speeds oh also light on recirc button went off I assume no codes.
7. after moving relays around my engine light came on ad the vsc light befor I bought a new relay switched them back then installed new relay and pulled neg cable to clear lights have not moved relays since I put in new one.

The cooling fan comes on for few secs and goes off but still no clutch. I am so confused does anyone have pics of fuse and relay lay out or wiring schematic and is it ok to run 12v to the clutch to check coil?

sorry I am old mechanic and this stuff is new age don't want to damage anything if i haven't already by jumping pressure sw.

Please help older guy with SI 2007 100300mi.

ezone

1) What is "enough psi to come on"?
2) fuses aren't ever clearly labeled for ALL the items they can be a part of. Use a test light, check ALL fuses. Both fuseboxes.
3) The compressor clutch relay is only labeled with a "snowflake" alone in the diagram on the lid of the box cover. A pic of a snowflake with a radiator is the condensor fan relay.
4) ok.
5) The switch with 3 wires is not a switch, it is a pressure sensor. Don't jumper it, you could do expensive damage to the PCM.
6) I'll take your word for it.
7) Oops.

I can't hotlink pics and diagrams from Hondas ISIS site, sorry.

The AC clutch field coil operates on 12V, so jumpering it to the battery is ok. (I start right at the relay, far easier, and that checks more than just the clutch alone. If no action, then go to the compressor connector.)
If the clutch won't engage (CLICK) with 12v applied directly to it, then you found a big problem. Last summer I changed several field coils/clutch sets for this problem on other Honda models (rather unusual, hmmmm) SOme were very intermittent and somewhat random as to when it would work or quit.

A couple other ideas here: If you CAN manually engage the compressor clutch with a jumper wire (from the relay socket) AND there is sufficient pressure in the system to engage the compressor, then I think this really might need an HDS scanner on it since there is far more in play than a simple self contained AC system.
The HVAC is connected to the Multiplex system, and them to the PCM. The PCM controls the compressor. The HVAC and MPX only make a request to the PCM. The PCM decides to allow or deny that request based on its other inputs to engage the clutch relay.
Being able to see and read the values that the control units see is a tremendous help in figuring out why it doesn't work.

The system pressure at rest should be close to the ambient temperature in Fahrenheit, depending on the ambient temperature. That is not a real indication of how much freon is actually in the system, but is only an indication of whether or not there is enough pressure in the system to engage the compressor. Even if only brief engagement.

Does the HVAC blower work properly? It must work in order to keep the compressor on. The HVAC unit has to see a blower motor feedback signal or else it shuts off the compressor. Typically, the compressor will come on for about one second then shut off (locked out) until the next key cycle occurs.

Check the thermal protector for continuity. It uses the other 2 wires in the compressor plug.

rescue46

Thank you for the reply.
Hope I didn't damage the pcm, I took the advice of 2 of the dealer's mechanics over the phone 1st one said to jumper the pressure sensor red to green and black to neg post on battery and it came on then off almost instantly then nothing.
2nd one said just jump green to red leave black alone same thing happened. but would not click in anymore, Yikes now you've scared me about the PCM.
2.then I switched the relays and after the lights came on put them back and bought new relay.

1. I will try the 12v to clutch first
2. then check the continuity of the thermal protector
3. the low side pressure was a little over 60psi and the temp was in 50 to 60 degree range
4. what is HDS scanner and is it at dealer only or hand held like scanner from autozone
5 worst case about how much $ are we talking. I am really anxious now! hope its something simple. oh and HVAC blower works great you are talking about the fan that blows air through the vents right? Heater will run you out of car.

ezone

60 PSI is plenty to allow compressor operation, so that isn't the problem right now. See if it cools before thinking about freon.

Dumb question: You have pushed the AC button and it lit up, right?

Continue with the other easy checks.
Jumper the clutch--- if it clicks on, I would then start the engine and set the controls to max cold and high fan, make sure it can work for about 30 seconds. If the system starts to get cold, then that eliminates a whole bunch of possibilities. Shut the car off as soon as you know the system can operate, because the radiator and condenser fans may not run when they need to.
If the clutch didn't click on, then you probably found a problem.



The HDS is the Honda dealer level scanner, it will access every available system on all Honda and Acura vehicles. It is miles beyond a code reader.
A well equipped independent shop that leans heavily toward Honda products may have it, but well equipped shops like that seem to be very few and far between.

Among other things, this scanner would allow you to read the pressure in the system through that pressure sensor in a data list, saving time, hassle, and possibly ruining something because you jumpered the wires without really knowing what they were for.

More data list: PCM; AC request, yes/no....and AC clutch on/off. That info splits the electronics in half, and would give me direction in a matter of seconds. From the comfort of the drivers seat.




Absolutely no idea on money until it gets accurately diagnosed.
Depends on what is wrong, who is doing the work, and how long it takes them to find the problem.
An experienced dealer tech should find the real problems much faster than a flunky. Dealers have flunkies too, just like most other places.
Many people seem to think that the only thing that can possibly be wrong with an AC system is low freon. Steer clear of this type.
Find someone with a stellar reputation.

Jack Smith

Really a nice stuff!