duder

I don't really know that much, but have read if the fans behind the radiator are not turning then there is likely an issue with the freon level, which is the case for me in addition to the compressor clutch not engaging.

Basically I just want to know which terminal to connect the positive side of the battery to the relay under the fuse box to manually engage the clutch as described in the video below. You can fast forward to 2:50 .

Attached is the photo of the relay. Any help appreciated.

jordan1794

1. Freon doesn't just disappear...if your car is low, it got out somehow...either by over-pressure venting or a leak. You need to figure out which it is first, otherwise you could be dumping money down the drain.

2. These cars actually have a bad relay for the AC clutch...I've heard of it getting stuck ON more than being stuck off, but if it is defective on yours then it might be the issue causing the fans not to run...

I know the original brand is something like OMRON,and the replacement brand is MITSUBA. I don't know the part number, but I know ezone has posted it in at least a half dozen threads so I'll try to find it really quick. Might be worth changing regardless, it will either fix the problem or give you peace of mind knowing it won't go bad later.


All this is assuming the issue is present on the 2007's, I don't know which years have the bad relays and which don't

jordan1794

From:
https://www.civicforums.com/forums/1...ay-2010-a.html

duder

Just getting back into this. Thanks so much for the reply. I just looked under the hood, and I do have all OMROM relays. Is there an easy way to test this before buying the MITSUBA? Just swap it with another relay in another location? Is it the same location that controls the clutch relay that also controls the fans?

ezone

Don't worry about trying to run the compressor manually.

If the system is really empty (below about 30 PSI) the compressor is disabled by the PCM--- and once you begin adding freon, the pressure sensor will detect the pressure rise and start the compressor running by itself--- if the engine is running and you have the AC system turned on.


But you had better make sure the system is really empty before you go adding more. It's too easy to overcharge these little tiny AC systems and cause poor or no cooling.

Connect your gauge to the low side and see how much pressure is in the system.


If the system pressure at rest is nearly equal to the outside air temperature--(i.e. If it is 85 degrees out and you have 90 PSI in the system) the compressor and fans should have already been operating and your immediate problem is not low freon.
It may be low but that's not why it doesn't run at all.

ezone

Oh yeah the clutch has its own relay, and OMRON is the trouble prone brand.
They can be tested but if you are looking to find out if it is sticking you would have to test while it's acting up and stuck.

Relay position #12 here is the compressor clutch:


Fans have their own relays, and they may be OMRON or another brand but they don't seem to have the trouble with sticking that the exact same relay will when it's used for the compressor clutch. IDK why, but that's what I've seen.

duder

So this is where I get a little confused. You say the clutch will automatically engage when you begin charging. When I first noticed the AC not working, I figured it just needed a freon charge, so I bought an AC Pro Refrigerant. However, I noticed the PSI was way to high to charge, close to 100 PSI with the AC on. So to make sure there was actually freon already in there, I released a bit real quick and noticed it was just neutral air coming out NOT freon (shouldn't freon be somewhat visible like a cloudy mist?) Keep in mind the clutch has never engaged during this process.

I thought that your clutch needed to engage before checking the pressure, right? Otherwise, are you really reading the actual PSI even without the clutch engaged?

ezone

Stop touching it. You have an electrical problem, not a low freon problem.

Well, if you let too much freon out you might have a new low freon problem.

It is freon, not air.
Freon in the closed AC system cannot turn to "air". Not at 100 PSI.

When the Freon is a gas it is clear and invisible.. Under pressure it can be both liquid and gas.

If you ever see freon in a mist it is because there is liquid freon vapor and/or oil in it.
Oil settles out throughout the bottom of the system when it is not operating so if you just burp a valve after it has been sitting you may not get any oil.



Static pressure vs. Operating pressures.
Both have great value if you know what and how.
With the system not running, pressure is equal throughout the system. That's static pressure.

With the system in operation, readings are taken of both high side and low side to evaluate the AC system, including determining if the charge condition is too low or too high.

Static pressure of 100 tells me you have more than enough pressure in the system to get it to kick on and run.




Static pressure is when the liquid (freon) has boiled enough to raise the pressure in the closed container to stop the boiling process.
(Same applies to any number of liquids and gases, Chemistry 101)

At 88 degrees F the static pressure of R134a is 100 PSI.

Reference chart:




Find and fix the electrical or electronic problem.



HTH

duder

Thanks for the static pressure chart and for the info. If you think it is electrical, should I start with the ac clutch relay or somewhere else?

ezone

You said the fans are not running--- so the PCM is not enabling the compressor and fans to run.

To me, that means either the PCM detects something that causes it to not allow AC operation, or the PCM is not seeing a request signal from the HVAC control panel.

It would be nice to be able to see a PCM data list to do some quick checks to verify the above.
I would have had my scanner plugged in in the first 5 minutes of parking the car in my bay.

------------------------------------------------

Ok ummmm.....here's a couple easy checks





try the HVAC self diagnosis and see if it returns any fault codes.

HVAC self diagnosis test

LINK: http://civic.hondafitjazz.com/A00/HTML/11/SNB6E11K73300000000BBAT00.html

Note: The first half of that article is correct, but clearing codes is not right for this car. If the problem is corrected, the code is supposed to automatically disappear.

If it shows any codes, then I may tell you to begin there, but it depends on what the code is.

-----------------------------------------------------

There is a 3 wire plug that sits above your alternator, it is the AC compressor connector.
Unplug it.
Take the plug half that leads to the compressor (has 3 red wires), Test the resistance of the 2 outer wires.
This is checking the thermal protector.
If it is open circuit, that will shut down the AC system.

----------------------------------------------------


Let me know if you come up with something on those.
Or not, and I'll look at some other stuff.

Got wiring diagrams for your car?

Interior fan DOES work, right?

Dr. H

What's the best brand to buy for a replacement ac compressor? My Honda Civic SI is also having ac trouble. I've been told it's the clutch.

ezone

You can buy the coil, clutch and pulley (separate from the compressor) through any dealership.


I almost always opt to fix the original compressor rather than install aftermarket.

duder

So a lot of this stuff started getting over my head so I ended up taking my car to a dude that works at a Honda dealership, except this dude has his one shop at home on the side and has been working on Hondas for 27 years and does it for less than half the price. Turns out that the 2007 civic has a common issue with the compressor clutch wearing over time creating a larger gap between the compressor and whatever magnetic apparatus there is that pulls the clutch in to run the compressor. At the time when the car was made the shim inside is supposedly necessary to create the right gap to function properly, but with the gradual wear on the clutch the gap is too large for the magnetic force to take place, he removed the shim to re-create the right gap. Simple process that took 30 minutes and now I'm back in business. Most places would have probably replaced the entire clutch and coil.

Thanks for all the help here.

ezone

Ah.
So the fans probably were running, just on low speed so they weren't real noticeable.

Glad it was something somewhat simple.
It can happen to any of the cars with high mileage, not just Civic.

Seems like by the time they get 150k-200k+ miles there's a dished wear spot where the clutch has been contacting the pulley, causing an excess of clearance.
I have a clutch and pulley like this on the workbench I've been meaning to take pictures of.




If it happens again, there won't be any more shims to remove and that would mean it's time to buy the clutch set.

Reverb2005

I'd actually love to see that picture! This gap problem seems like quite a common problem on aging Civic (and other cars in general, as described).

Would be nice to see a new and old version....

ezone

Through the magic of television:


Note the mating surfaces of the new parts are flat, and the darker ring in the new pulley is a layer of something like cork used as to cushion the engagement.









Note the ruler in the last pic is not laying across the center hub, it is laying flat across the back half of the plate behind the hub to show the deep wear in what used to be a flat clutch plate. It's just an optical illusion making it appear to be laying on top of the center hub.