Hi everyone, my first post here, nice forum
I have a problem and I hope someone will help me with it. My air conditionning unit (AC) doesn't cool the air. Here's what I've done (all day today):
Tested all the AC-related relays and fuses (under dash and under hood). The red wire going to the temp control sensor from the relay is fine and there's 14 volts on the Field Coil (right after the Temp sensor) when the car is running and the AC switch in ON.
The air is still warm and the heat exchanger (under the glove box) doesn't get cold. The blower fan (under glove box) is spinning fine. The fan on the heat-exchanger (outside, on the right of the radiator) is turning too.
Got 2 cans of R134a-compatible gas and filled the system, same problem.
When the AC is turned on, the RPMs go higher (from about 700 to about 1200) and go to idle slowly. When it is turned off, the RPMs go high again (to about 1000), then drop to 700 slowly.
If I take two long wires from the relay that activates the compressor and put my ear just above the compressor (car is running at this time), and I short them, I don't hear any clicking sounds (as suggested by the service manual). I wonder which part should click and what happens when it clicks.
Since I got this car (2 years ago), the AC never worked.
I also have the Haynes manual and the original Honda manual. Tried everything there, no help.
Car is a Civic 97 EX automatic, 4-door.
Open for suggestions and experimenting
Thank you all for answers.

 

It isn't clear from your description if compressor actually engages? You should hear a rather loud snap or clunk at the compressor and the clutch plate on the front of the compressor pulley (with flat springs) should start turning.

I would test it with the engine off first. Disconnect the wire at the compressor and jumper the compressor to the battery. Again a loud snap or clunk should be heard when the clutch engages.

 

I'm going to test it right now.
I don't remember hearing any loud sounds coming from the compressor. BTW, when you say the compressor wires, you mean the field coil (solenoid), right?
Keep you updated...

 

Right. I think there is a single "hot" wire and the other end of the solenoid is grounded at the compressor (bad connection there is another potential trouble spot).

The sound you hear is the same clunk you hear from other cars at a stoplight with your windows down because their A/C works....

Do not jump the compressor to the battery with the engine running as this can cause the compressor to run without normal control. Excessive pressure can build up and damage your system.

 

Even if my windows are down, the music is blasting over any other sounds

Just did a quick test. Connected the battery straight to the compressor. When the wires touch (connection is made), no sound is heard from the compressor (car is off). When I take the wires apart, there's a slight "thump" sound (as if metal hits metal, but one of metals is hollow). But there's no click or any other sound when the wires are connected. Also, taking the wires apart produces a spark (so the coil of the solenoid is working).
My guess is that the solenoid/clutch are jammed (maybe rusty). I have to find a way to take them apart without letting the gas out (just filled it yesterday, 50$ for 2 cans of R134a).
What do you think? Maybe throw some WD40 at them (being careful to miss the belt).

 

When I was playing with the wire (see above post), I connected it to the battery many times (about 30 or more). I did it quite quick (about 1.5 hits per second). Now the AC is working fine and I'm happy.

I know that this car, before I bought it, was not used for a long time (even the tires became flat on where they were touching the ground, which made me change them to avoid a crazy shaking at high speed). I guess the compressor's clutch got rusty and wasn't connecting the compressor to the main pulley. By playing with the wire, I got it to unrust. I noticed it thanks to mk378 (look 2 posts up). He suggested to look at the clutch's disk and see if it was turning. It wasn't, but then I realized that the red power wire going to the compressor was disconnected (by me, 5 minutes before that to allow the direct connection to the battery). So, after hooking it back and getting inside of the car, oh so great...the air was cool and getting colder by the second.

I don't know if spraying some WD40 on it will make it even less rusty (avoiding the belt, of course )

The only concern now is the presure in the AC system. I know that it needs 19-21 oz of R134a and each can of gas I got was 17 oz, so I couldn't know if I filled too much or not (I used 2 cans, but the second one is not empty yet). Maybe I'll go to a shop to ask for pressure measurement, I hope they don't charge me much.

Thank you all (especially mk378) for help. I think I'm the AC system expert now, lol, after 2 days non-stop working on it (well, I went to sleep in between).

 

Could've just been rusty. The main problem that will cause what you were experiencing is the gap between the clutch plate and the pulley becomes too wide. The clutch will engage sometimes but not other times, especially when it is hot, of course. The clutch does not require lubrication. It is metal on metal, similar to what happens when brake pads are worn down to the metal. They GRAB. Not what you want for stopping but ideal for this situation.

The gap can be adjusted by taking the nut off of the shaft on the front, take the plate assembly off, and look for little shim washers on the shaft. Take some of the shims out and reassemble. If the clutch drags when you spin the pulley by hand, obviously it is too close and you need to put shims back in. You will probably need to unbolt the compressor from the engine to do this. But don't disconnect the refrigerant lines, just unbolt the compressor and pull it down under the car some so you can work on it.

That's just something to keep in mind for later. The general rule is if it's working, leave it alone. Certainly don't add any more refrigerant while it is cooling. The only way to be sure how much you have is take it out and start over. If you go to a shop with a recovery machine they can take it out, weigh how much you had, and then put it back in with the right amount.

 

Oh, can't they just measure the pressure on Low and High sides and compare with manufacture ratings?

 

The pressure will tell if it is way off, but the best way to ensure peak performance is to go by weight to the manufacturer's specification. There is a fairly wide range that will give acceptable cooling, so if you have acceptable cooling just leave it alone.

 

Oh, great, thanks!!