investigator

I have a 2002 Honda Civic. When I bought the car, the AC compressor was unplugged. I plugged it back in and it did not engage. I checked the pressure and it was a little bit low. I jumped the relay with the pressure gauge on and watched the pressure drop when the compressor kicked on. I added some refrigerant but it eventually leveled out and when I pulled the jumper out, the pressure spiked to 120+ PSI on the low side. The clutch does not engage with the relay though the relay doesn't looked charred or broken externally. Is this a problem with the compressor? It's still not blowing air though it appears to affect the pressure when it is engaged.

Thanks!

ezone

You apparently were able to make the compressor run manually (electrically).

A set of pressure gauges would be used to read high side and low side to evaluate the system condition/operation at that point, and see if it cools.

The rest of the car is apparently not able to operate the compressor for some reason. More troubleshooting is needed.


i think you really don't have enough info to make a good assessment yet.

investigator

I don't have a gauge for the high side but I'm thinking the compressor is shutting off due to low pressure on the high side. I'm thinking the expansion valve is stuck closed and it's restricting flow. I know this because the low side lines are hot (ambient temp). But I know for a fact the compressor is running.

Since I don't have a vacuum, I was gonna replace the expansion valve and then fill the system to test my theory. If it works, I'll take it to a shop so they can evacuate the moisture I let in from taking it apart and refill it. I'd like to skip that phase but it didn't end well last time.

Thoughts?

ezone

Many.

Wrong. You did give enough info in the thread that I can evaluate this part from my recliner.

You don't have the equipment necessary to evaluate an operating AC system. Do you have equipment and patience to figure out the electrical side that (most likely) caused it to stop operating?


Most of the AC problems I see on these cars are not freon related. Easily 75% are electrical issues that stop AC operation. You've now added more freon to the system, that throws yet another possible problem into the mix.


But your first post stated the compressor does NOT run on its own. Which is it?
The compressor is not running....
The expansion valve cannot cause the compressor to turn off.

I'm not saying the TXV is in perfect condition, but your reasoning for condemning it is incorrect.

You may want to take it to a shop that has someone smart enough to diagnose the problem(s) accurately. Those individuals seem to be few and far between.
Also, multiple problems may require multiple repair attempts.

investigator

But compressors clutches are designed to disengage when there is low pressure and there is low pressure. Obviously it's not an electrical issue because when it's manually engaged, it still doesn't work. There's only two electrical parts on this system and I bypassed both of them. The fan and the clutch. All that's left is the temp sensor and that's bypassed when I manually engage the fan. So, it's likely the valve. It can't be anything else other than the compressor. These things aren't that complicated.

ezone

Not according to you: There is sufficient pressure in the system for it to operate.


Like I said, it's probably got more than one single issue.

You still don't have enough equipment to properly evaluate the system.
Good luck.

investigator

Is it not normal for low pressure to spike when the clutch turns off? I've seen it before on a few vehicles. When the compressor and the AC fan turns on, it drops the pressure to the normal pressure which was really low.

ezone

Yes, that's normal.

What are you calling 'low'?

FYI this AC system does not monitor system pressure on the low side.
The compressor will not be shut off even if the low side is running in a vacuum.
What now??

investigator

I think it's obvious that if the low side is low, the high side is either high or low. Really low is 15-20 PSI. I'm still thinking it's the expansion valve stuck closed or open which would be determined by the readings on the high side.

ezone

Not necessarily......but

You said don't have a gauge to read that.


You still haven't said what your low side reading was.

investigator

It was reading 15-20 except the first time I started the compressor, it dropped to less than 15. So I added some to see if I could get the system going and it didn't work so I bled it back to the way it was.

ezone

Guess I missed that you gave those numbers. I can't read.



15-20 PSI CAN be acceptable under some conditions, like low ambient temperature.
The low side reading only tells half the story though.

investigator

No worries mate. However, it's definitely not the ambient temperature because it's 98 degrees here in Houston. At first I thought the compressor wasn't pumping but it changed the pressure reading so it must be good unless there is an internal seal that failed within the compressor allowing the high and low side to meet. The valve is on $20 plus the oil, so I think it's worth replacing anyway.

ezone

You will still have to figure out why the compressor isn't running on its own. Replacing the TXV can't correct that.

investigator

If the compressor clutch isn't engaging because of a pressure issue (either too high or too low on high end) then replacing the valve and allowing it to function correctly should theoretically fix that.


Don't you think?

ezone

You could just test for continuity at the pressure switch and see if it is open or closed.

You stated 120 PSI static pressure when the compressor was shut off. That is neither too low nor too high. 120 PSI should have that pressure switch contacts closed.
That is sufficient to get the system to turn the compressor on....but your car won't even turn the compressor on at all.
Why not?


You could get a service manual and wiring diagrams and see what is really involved in this cars HVAC system electrically. It's probably not as simple as you want it to be.

You can search this forum and probably find about 8000 AC related threads I have replied to in the last few years.....6000 of those will be about the 7th gen cars like you have.

investigator

Allow me to clarify the whole thing. So, when I bought the car the other day, I checked the pressure on the low side with the car off. The pressure was 12-15. I noticed the compressor was unplugged from the power so I plugged that in. When I manually engaged the compressor with a paperclip by jumping the relay, it dropped to almost zero. I figured the total pressure in the system was too low. So I added some refrigerant. I got it to reasonable pressure level while jumping both the AC fan and the compressor clutch with paper clips. When I pulled the paper clip out and stuck the relay back in on the compressor clutch, it still did not engage however, the system was not cold either. When the clutch shut off the pressure now at 30PSI while running spiked to 120 like you said it's supposed to. So as you said, there is likely two problems. I'm thinking someone pulled a plug somewhere else as well as they did on the compressor. Maybe that temp gauge on the evaporator core. But it still does not make sense the system not being cold because the compressor is compressing. The only part of the system that would prevent it from being cold with a working compressor is the valve. I'd like to get the system cold first and then work backwards to the electrical issue.

Does that clarify it a bit? I apologize for lacking too much detail prior.

ezone

NOW this make more sense. The low pressure cutoff is approximately 35 PSI, so with 20 in the system it will not be allowed to turn the compressor on.
The system was nearly empty......and you added some unknown quantity of freon.

What's reasonable? (NVM, I see 30 psi below)

You could still be very undercharged or wildly overcharged....without knowing the high side pressure you only get half of the picture.



The car still has another problem besides the system being low on freon. There are several fairly common problems it could have.

These AC systems are made with very small capacity with very little room for error. Just a couple ounces over or under spec can dramatically affect cooling efficiency. This is just one reason a professional charges an AC system by weight.

For all we know it could cool ok if it had the proper charge in it.
Your system is supposed to hold between 500-550 grams yes?

System pressures will equalize after the compressor stops running. That usually takes a little time, and one would watch the high side to know what its pressure is at the same time and see if the time span is reasonable.

Even with the low at 30, the high can be all over the map and you'd never see it on the low side.


I doubt it, most would only unplug one item to make it stop.

Probably something either was bad all along, or has since gone bad after someone unplugged the compressor.
Is the compressor noisy when it runs?

The typical failures are sometimes rather expensive to repair.
Doubt it, very low failure rate on that item.

Search for how to do an HVAC self test, that should show if the evap temp sensor is a problem.....or if anything else that can be monitored by the controller might be a problem. (If you had a decent service manual for the car, you might have already figured this part out.)
Or incorrect charge amount.
Or a blockage anywhere in the system.
And more.
You really don't know how well the compressor works either, you only know it is able to pump something.

That high side pressure gauge would come in handy right about now, along with a known freon charge quantity and some basic temp checks around the system while it's running.
Ok.
Much better, thanks. I can be overly technical in my thinking and lack of certain detail is frustrating, sorry if I seemed rude.

investigator

Update:

I found that the vehicle was in a front end accident. The condenser is really beat up, it's bent in almost a U shape, I'm surprised it's not leaking. I'm sure the lack of cooling has caused the compressor to fail or it is clogged from the condenser being bent. That definitely has to be replaced.

ezone

Really? The system was almost empty when you got it, so where did that freon go?

That damage MIGHT explain why the system leaked the freon out..but the rest of your assessment about clogging or ruining the compressor is only guessing.
Again, these guesses could be evaluated and proven true or false if you have the correct equipment.

I have seen some seriously effed up condensors that still do the job though. A condensor is not a single tube snaked back and forth for a mile, it's multiple paths through and it would take a whole bunch of pinched tubes to block flow to a critical extent.

Any wiring damaged at the top of the core support?

investigator

I'll give you a new bit of info. I replaced the expansion valve and recharged the A/C and added PAG oil. I jumped the compressor and the fan again and the needle was jumping up and down. The air started blowing a little tiny bit cold. Maybe 5 degrees less than ambient temperature. However, the compressor was putting a LOT of stress on the engine, almost stalled it twice in neutral. The belt needs replacing and is squeaking but I'm starting to think it's just a failing compressor. Tell me, I know you'd want to know the high reading but what else would you do knowing these facts?

ezone

Did it load down the engine that bad when you first tried operating it?

Check belt tension and adjust if necessary.

How much freon did you manage to get in it?
How much oil?

How cheap is a set of gauges from Harbor Freight, and can you find any cheaper than theirs online? http://www.harborfreight.com/ac-r134...set-60806.html

Will Autozone let you borrow/rent a set of gauges for little or nothing?

investigator

I put about 8oz in and the low side was hovering around 40-50psi. Seems like an awefully low amount for going from totally empty to full?

investigator

and about 4oz of oil. I used a fill chart and it said 4.5oz for PAG oil.

ezone

Your car should still have a spec sticker that tells the refrigerant capacity.
I also posted the amount earlier.
The spec is not 8oz.

investigator

The chart says 18oz, but it's reading high on the low side after adding 8oz, which tells me something is wrong.

ezone

What are you considering "high"?
How high do you think it should be?
Do you know just how high can it actually be and still be acceptable?

Again, without the necessary high side pressure gauge you can't further evaluate what you are seeing.

8oz is not enough for that system.

ezone

Non-condensables in the AC system, that can screw with the pressure readings....

Was the system fully evacuated with a vacuum pump before refilling with freon?

investigator

The needle is all over the place on the dial. It goes up and down and makes the car idle all wacky. Last time I saw that, the compressor burned out on my old car. I'm really thinking the compressor just needs replacing. I also noticed the A/C button is constantly green and won't go off when I press it. Definitely an electrical issue thrown in there as well. I'm just gonna take it to a mechanic friend of mine. Typically, I'd just figure it out on my own as I have in the past but I just don't have time or the right equipment.

However, thanks for your help. I really appreciate it. =)

ezone

I told you there would be.
Is this friend intimately familiar with these particular cars?
Is he any good with electronic troubleshooting?
I can walk you through this if you are willing to do the legwork. Replace the control panel LOL

Actually, make sure the AC system has enough pressure to run first....

Then pull out the entire HVAC control panel from the dash and locate connector/terminal A4 (blue wire) and ground it, see if that makes the compressor and fans kick on. If that gets them to kick on, replace the HVAC control panel. (The section with the 3 dials, not the 3 switches.)

If not, there's a lot more to check.