Jordan Mullen

Last summer my wifes A/C stopped working, I found a leak at the low side valve, replaced, filled it up and it worked until about two weeks ago.

Went to fill it up this time and it seemed like it had too much pressure initially, so I let some out and that worked for about 5 minutes. What is happening is that as the A/C starts running the pressure builds on the low side and eventually it cuts off.

When you first start the car it runs fine and pressure looks fine. As it continues to run the pressure builds (needle eventually max's out) and it stops cycling. I'm using a cheapo guage, but it has repeated the same thing about 5 times, and the pressure it shows matches what the system is doing, so I believe the guage is fine?

Shortly before it stops the clutch/compressor will make a sqealing sound for a second when the revs get high.

I put some dye in it and found a small leak on the hose that runs by the bottom of the radiator/condensor at what looks like a fitting on it? This hose runs along the lower rail that the radiator fits in, then up under the air box, then towards the firewall by the fender. There seems to be some fitting connecting two parts down by the bottom of the radiator. I don't think this is the problem as even at start with the compressor running the pressure is fine.

Not sure if something is making the pressure rise, or if the clutch stopping is a by product of something else and the the rise is a pressure match to the high side. The compressor still runs as the pressure builds though..

Please give me some leads here. I have not tried to bypass via the pressue switch as it looks like it is doing it's job and shutting the system down when the pressure gets too high... though that might not be a bad thing to try?

Former User

After replacing the valve, did you replace the receiver/dryer, place the system under deep vacuum, and then refill it with the proper weight of refrigerant?

Jordan Mullen

Nope, so their could be air/moisture in the system. Would be kinda strage for it to work for 10 months, and the crap out because of that... could be though... or that could have killed the compressor.

Former User

If you lack the equipment or expertise to do the job correctly, then take your car to an A/C shop to have the refrigerant recovered, the receiver/dryer replaced and small O-ring leak fixed, and the system evacuated under deep vacuum and recharged with oil and the proper weight of refrigerant. Only allow a reputable A/C shop to do the work.

Jordan Mullen

I can get some real guages, and a vac pump. Not a big deal, honestly I was bein lazy. You are reccomending to replace filter/dryer, vac it, fill etc.. and see if that fixes it?

If not, can you reccomend a good test for the compressor. I'm assuming the sqealing noise has something to do with the clutch plates?

Former User

The first step is to stop running the A/C and:

...then go from there. My guess is that all will be fine with your A/C after this^ is done.

I think the squealing noise is caused by the A/C belt slipping on the compressor pulley due to the resistance in turning the pulley when the pressure in the system becomes very high.

Jordan Mullen

Thank you Ron, I will report back when this is done. Your slipping belt theory sounds right, I have felt some resistance at the pedal after the ac has been running for a bit.

pato_olivos

Hi fellows,
Anyone know the pressure at the low side with Compressor ON and OFF for a 00 Civic coupe?

I have read in other threads that pressures are: about 100psi (compresor off) and between 25-50 psi (compressor ON). That is correct?

(hfc-134a)

thks!

Former User

That's about right. The exact pressures depend on the temperature.

pato_olivos

Thanks for the response, Ron.

You know the pressure at an ambient temperature of 24 degrees (°C)? I have a table but not sure how to use it.

Former User

With the A/C turned off at 24C at sea level, the pressure of R134a is about 93 PSI. This is the static pressure of R134a. Note that in most cases the static pressure reading does not tell you whether or not the refrigerant level is good, low, or high.

At 24C with the engine running at 1500 rpm and the A/C turned on MAX, the low side pressure should be about 28 PSI and the high side pressure should be about 260 PSI.

Hybrid96EK

I'm finding an issue with your posted high side pressure. 24 degree celcius is 72 Fahrenheit. High side pressure should be approx ambient temp + 100. So at 72 Fahrenheit he should see 172 give or take a few.

Former User

My low and high side pressures were taken directly from the pressure-temp chart in the service manual.
Also, 24C = 75.2F

Chart:

shorepatrol

I just went through the EXACT same thing on my 96 civic. You can replace everything yourself. I did the expansion valve compressor, condensor and dryer for less than $500 with a 2 year parts warranty. I started with just pulling it down and recharging. Made zero difference. I pulled the evap and cleaned it (It was half full of leaves and dirt), replaced the expansion valve while evap was out. Flushed out the system to make sure there were no restrictions or garbage in the lines. Pulled it down and recharged again. Made zero difference. New compressor, condensor and dryer and it works like new. Big surprise , I know. It works after everything was replaced. But hey, it works. And for at least $1700 less for what a shop would've charged. Be more than happy to walk you through it as you will need to replace all of the above to get the extended warranty. Hardest part is getting evap and dryer out and back in. Compressor and condensor are a piece of cake. Takes just shy of 2 , 12 oz cans of freon to charge and about 5oz of oil.

Jordan Mullen

Compressor is spinning fine when it should, no grinding, I do not think I need a new compressor. But fully aware I can change it as I have done it plenty of times before in other cars.


I did not change the FD last night as I didn't want to open up the system again just yet... and the drier is in a funny spot so it will take a bit to get it out.

I did however get a real set of guages and a vacuum. Sucked it down for about an hour and it was so low on freon compressor would not engage. Added a can of freon and sucked it down again for about 30 min.... so low on freon compressor would not engauge. Added two 12oz cans and got it spinning again... 70F outside about 30/225 on the reading at 1500 rpm, let it idle for 20 min and down to 25/175 @1500 rpm.

Vacuum went down to -29 when I was running it, but it is obviously loosing pressure. So I think I have a leak on the high side somewhere? I checked everything I could see with the blacklight and I only found stuff on the hard line that the low side hooks up to, and then down on the plastic below the line. Pulled the insulation off and sprayed it with soap/water and did not get any bubbling. I made mess putting the dye in though so I think it might have dripped down this pipe as it gets condensation when it is running?

Does anyone have a diagram of the AC lines etc.. I cant find anything. Any other ideas where to look? Running cold as can be right now, but I assume not for long, thanks. Car was recently in a front end accident, but I cannot find any evidence of a leak.

Former User

If you look at the chart I posted, the refrigerant pressures are not too bad. The pressures may have dropped due to a leak but there are other possible explanations, such as the A/C system chilling down after running for a while.

Below are the conditions that the service manual recommends for measuring the refrigerant pressures. This allows you to use the temp-pressure chart I posted. Replace step 1 with hooking up the manifold gauge set.

Jordan Mullen

Good point, the delivery temperature did drop a good bit, so that makes sense....


However there is not room for 3 cans of freon on there, and I wouldn't think it would get that low because of running a vacuum on it. I do think it is a smaller leak since the vacuum got nice and low. So most likely it will be hard to find

Former User

As long as the A/C blows cold, I would just monitor the pressures once or twice a week and the appearance of dye throughout the system.



As you did not replace the receiver/dryer, you also need to be concerned about moisture in the system in the long run. Water reacts with the refrigerant to create acid, which can over time destroy the A/C system.

Jordan Mullen

I'm aware, if I don't find a leak in the next few weeks I'll go ahead and replace it. No sense in doing it twice if I have to replace something else though. That diagram helps a ton, thank you for all your help Ron! How hard is it to get a visual on the evaporator? Do you have to pull the whole dash?

Former User

Start by just removing the glove box.

shorepatrol

My compressor spun fine to, no grinding. All the way up until the pressures went through the roof. Squeal came and then it kicked off. To get the dryer out, you just need to remove the front head light, unbolt the wiper washer bottle and wrestle it out from the bottom. As for the evap, remove the glove box and the support bar behind it. Remove the battery and unbolt the 2 lines running into the firewall. There are only a few bolts holding evap in , all easily seen. It should drop out fairly easily.

Jordan Mullen

Don't want to pull it out, just want to check it for leaks. Compressor is acting correctly after vacuum and with correct charge. If it was bad it would continue the same thing regardless. Thank you for your help, you insturctions with the drier will come in handy.

shorepatrol

No problem. The 2 lines at the firewall have o rings on them. That's all you will be able to check with out completely pulling it out of the car.