Model: Grand Cherokee
Engine Size: 4.7L
Refrigerant Type: R134a
Ambient Temp: 88
Pressure Low: 0
Pressure High: 150
Country of Origin: United States
Father-in-laws jeep blows air, barely cooler than ambient. He claims that he bought the vehicle back in Sept of 2009 and the A/C was working very good. Summer of 2010 it was working good and then one morning as usual before going to work, he turned on the A/C before leaving and he saw what he said looked like smokey mist coming out of the vent. He immediately shut it off. Then that evening after coming home from work, he turned the A/C on again and there was no "mist" and it didn't seem to cool as well anymore. The system does have a very faint cooling. The compressor does come on also when A/C is turned on.
I checked ambient pressures with vehicle shut off after it was driven some of the day: 120/125
With A/C on High, windows open, blower high:
(Idle) 5/155 with 96-degF vent output
(attempting a steady 1500 RPM) 0/150 with 93-degF vent output
I wasn't sure how much refrigerant was in it, so I recovered it: 1lb - 9oz total (recommended fill is 27oz = 1lb - 11oz) So it appears the charge is good. I ran a deep vacuum for about 30-minutes and it held good at 29"Hg for about 30-minutes until I disconnected. Doesn't seem to leak and full charge refrigerant was in the system. Make sense to anyone?
Should I recharge it again or does it seem maybe a bad component? Maybe expansion valve? I'm just shooting from the hip. Any tips are greatly welcome.
PS. If or when I do refill his system, is it recommended not to use the recovery R134a to put back in the system or should I pull it from my new 30lb tank. I wasnt sure and thought I heard not to put recovered refrigerant back in due to contamination, etc. The A/C recovery unit I have has a filter. I was just wondering.
Edited: Mon May 30, 2011 at 8:30 PM by scusack71
When you have low side of 0 on a properly charged system, that would be a blockage, usually a TXV problem. It can also be a blocked condenser (if measuring the high side before the condenser) or receiver drier. It being a used car, you have to beware of sealant.
The high side is measured at the inlet of the receiver/drier (which appears to come from the condenser). Everything after the reciever/drier is the TXV and then the Evaporator. Does this seem like that would either indicate TXV or Receiver Drier or both?
If it is the TXV, can I pull it apart and immediately cap the system, replace the TXV, reconnect everything and just draw a deep vac and then service with R134a? Or am I missing some steps?
If its the drier, it may be a little more work. It's easily accessable but the drier has a fixed rigid outlet line to TXV and another rigid inlet line with a flex hose connected to the outlet of the Condenser (all one piece). I assume that would require me to attempt to retrieve ALL oil from it to figure out how much came out of the system to replace with the appropriate amount?
I'm not sure any sealants were ever used but I see your concern with that though. Toss me a recommendation and I'm willing to start somewhere. Thank you.
Edited: Mon May 30, 2011 at 9:38 PM by scusack71
You had plenty of pressure after the condenser, so it does not appear that it is blocked. If receiver is blocked it will usually get cold on the outlet pipe, which is not normal (blockage is acting like an expansion device).
Edited: Mon May 30, 2011 at 9:41 PM by mk378
Ambient Temp: 76-DegF
Ok, I changed out the expansion valve with high hopes... but my luck has prevailed again....still 85-degF vent temps... but probably since my low and high pressures are both equal after I was only able to service 19 of the required 27oz (couldn't get any more refrigerant in the system). I performed two great 30-minute vacuums with no degradation of vacuum (29"Hg). Also, serviced through the low side only and high side cranked shut... in case anyone asks
The funny thing was that it started to service very nicely when the low pressure was about 40psi and the high was about 100psi, which was positive compared to my original pressures before changing the TXV. The clutch was engaged the whole time. It was weird since the clutch was already running, I heard that clutch cycling sound when it makes that click noise. At that point it seems like the low pressure just popped up to 87psi and the 100psi high pressure dropped to 85psi as well. Did something open up? Did my new TXV take a dump?
I have a feeling I'm going to have to evac the system again (bummer) and take another step. Any tips ya'll. I really appreciate your help.
By the way... just FYI: The high pressure port is located between the drier and the TXV. The low pressure port is located between the TXV and compressor.
Edited: Wed June 01, 2011 at 8:22 PM by scusack71
It appears that the compressor stopped. Find out why. (Is it because the air inside got cold enough?) Start it up again and if it comes on get the rest of the charge in.
Edited: Wed June 01, 2011 at 8:44 PM by mk378
I verified while the charging process was running that the clutch was engaged and only shuts off when A/C is shut off... or am I looking at it wrong? Can the clutch be engaged and compressor not be running?
Back to your question... the temp coming out the of vents never got cold (86-degF).
So, do you think if I'm able to complete the last 8oz of charge... all may be peachy? Thanks for responding mk378!
The compressor may have let go inside. If the clutch plate is spinning it should be pumping. You're not going to be able to charge like that, and it wouldn't help anyway.
I tried to service it again but only was able to get 1.5oz in... plus the 30lb bottle could have been warmer... the temp had dropped to 71-degF by this time.
Edited: Thu June 02, 2011 at 7:57 AM by scusack71
So you believe that the compressor may still be running, even though my low/high pressure are equal (apx 85psi for both)? Based on mk378's comment, the compressor may have "let go"? Not exactly sure what 'let go' means... I was waiting for a reply to my question after that comment to see whether it seems as if my compressor failed or not.
I'll have to get the bottle warm (I have a 30lb) and try to get more in. Also, I have been purging air out of the yellow service hose at the manifold.
Also, you recommend me using my recovered refrigerant.... can I use it in another vehicle since I have already filled this vehicle with my 30lb bottle? Just wanted to make sure that the refrigerant pulled from one vehicle wont hurt another if i don't put it back in the original car. I know... sounds like a silly question... but just want to make sure.
Edited: Thu June 02, 2011 at 12:59 PM by scusack71
I tried to service it HVACNY but as I mentioned in my previous post, I had 85/85 and my bottle couldn't push it in. I even put the bottle in my utility sink with warm water hoping it would help build some pressure to service, but no luck.
I guess I'm still trying to get my question answered whether the compressor seems toasted? I can rotate the clutch plate clockwise and it appears to have some resistance (like pressure) when I try to turn it quicker. If I turn it real slow, it turns with less resistance. I know I'm underservice, but if I can't get it in what would be the cause? Would the extra 30% refrigerant I need make the low pressure drop? Could I have put in a defective TXV? Or failed pump?
As I said before, when I started servicing pressures were rising nicely when I got a little over 1lb in there then the clutch made a cycling rotation noise for about a second (even though the clutch plate had been rotating throughout the filling previously) and when I looked at the guages, the low pressure had caught up to the high pressure and equalized.
Also, tonight when I tried to service it up, the low pressure exceeded the high pressure at 100/75. I know I've heard some say it's impossible.... but that's what the guages said... unless my guages just took a crap. I don't know. Any tips to troubleshoot would be great. Thanks again for the help guys.
Edited: Fri June 03, 2011 at 9:41 AM by scusack71
Highly doubtfull a new TXV is bad,it does happen occasionally,but not likely.So you have eliminated that.In your first post you said the compressor was working,so im a little confused.You also still havent gotten in the correct charge.If you took out 25oz you should certainly be able to get that back in.Try recovering the gas and starting over.See if the compressor starts cycling and taking in refrigerant as your filling it.You also may not be recovering correctly,or doing something wrong on that end,im not their so were going by what you say.When you recover the gas refill your system from your 30# drum instead of your recovery tank and see if it makes a difference. Also as a shot try jumping the low pressure switch to see if the compressor runs,could be a bad switch,it happens.
Edited: Fri June 03, 2011 at 10:03 AM by HVACNY
Yes, it was cooling originally, but when I was charging it the first time at some point the pressure looked good as it was filling 40/110 or so. Then I heard what sounded like the 'click/rotation' noise as if the clutch had just cycled one time.... however, the clutch plate has been rotating the whole time. You see... my point is that the clutch had always been running but hearing this clutch rotation noise for about 1-second confused me since the clutch never stopped rotating. The highlight of this is that this is at the point when I looked at the pressures, there was now no differential between high and low (equal) at about 85/85. How can that happen? That's why I was questioning the compressor and also mk378 made a comment about "The compressor may have let go inside." That is why I believe the pressure switch should be ok since the clutch always turns on when the A/C switch is activated.
Unless my story sheds any more light than before, I'll do what you recommend with me starting over, I'll give it a shot with the recover and refill again with my 30lb R134a.
Also, I had always used the new refrigerant from my 30lb bottle since I wasn't sure if it was safe or advisable to reuse it or not. Thank you for getting back. I'll post back unless you have any additional info you can feed me. Thanks
I'm going to try and evacuate the system again and recharge and watch everything closely. I'll post back with results. Thanks
Edited: Sat June 04, 2011 at 4:32 PM by scusack71
Well, I recovered all refrigerant to attempt another recharge. A little disappointed, I was only able to recover 7 of 19oz I put in the other day. I'm not sure if there's much of a loss from line connections/disconnections but 12oz went somewhere. It may have been my TXV replacement or maybe there all along???
This time I connected my RobinAir to draw a deep vac again and ended up leaving it on for about 1-hour since I was occupied with another project. It drew a good deep vac and I let it sit for about 45min to an hour still tinkering with my other project. Last time I serviced it I only waited 10min with pump off to see if there was any degradation, but this time after leaving it isolated for 45min it dropped from 29.5 to 10"Hg. I thought either leak or boil off... but more of a leak. So I turned on the pump again and left it on for about 15min and shut if off and let it sit for about 10min since it was getting dark outside and my father-in-law needed to go. It may have dropped 1"Hg but not 100% sure... probably should have hooked up a micron gauge?
I'm going to charge it with a litte and check it with my sniffer. I see no oil leaks and I've now since learned with my 96 Grand Am (another post) didn't leak with a vacuum but did with a positive charge of refrigerant since I was able to find a belly leak on its V5 compressor. I love the challenge of trying to find the problem but dont like all the time consumption in trying to find the culprit (vac, charge, recover, etc) Oh well
Edited: Sun June 05, 2011 at 8:27 PM by scusack71
It appears from the posted pressures and operational conditions that the compressor is no longer pumping. Try rotating the compressor drive (the plate on the front of the clutch) with the engine off....determine if there is any resistance in the rotation. Your should feel a slight resistance and then a fall off of pressures. This of course is not a true valid test for compressor operation, however, if there is no resistance a this point, it is quite possible that the compressor is not longer producing pressures...hence the equalization of pressures.
If this is the case, along with a replacement compressor a strong suggestion would be to replace the condenser as part of the repair. The TXV should be removed and inspected for possible debris contamination. The evaporator should be flushed utilizing an acceptable flush chemical. Considering the low ambient temps a good air purge of the evap would possibly benefit in removal of residual flush chems. the Rec/Drier/Filter should be changed also.
The system should be lubricated with the correct lubricant. Now comes the tricky part.....the compressor was never designed to be a 'suction' pump for refrigerant. This is something that techs derived over years of learning short cuts. Yes, it is known that this is done hundreds of times each day, however, the compressor is operating without sufficient lubricant migration during this 'charge' procedure. This may result in premature compressor failures, esp on Denso compressors. These units do not utilize the standard teflon type piston sealing ring but the pistons are actually coated with the teflon type material. This material can be damaged during a recharge procedure such as is being utilized. This type damage may result in reduction of compression pressures.
If it is your desire to complete the repairs...then by all means do so...but have the system professionally charged by someone who is able to utilize the correct recharge equipment. If you are considering the completion of other AC repairs....invest in a set of scales and a heater blanket for the refrigerant cylinder. This will allow for a complete system recharge without ever starting the vehicle and using the compressor to 'suck' refrigerant into the system. Several benefits....a major one is that now the amount of refrigerant in the vehicle is a known factor.
As a personal note...what type recover procedure is being utilized that will only recover a small percentage of refrigerant from the system?
Another issue a restricted condenser may not indicate a 'cold' outlet as stated earlier. The discharge pressure/temperatures are a true indication of a possible condenser restriction. A test for inlet and outlet condenser temperatures is a valid determination for a possible restriction. The temperature drop due to a restriction may actually indicate a 'high' side (liquid) pressure that could be well within a perceived acceptable pressure range....or may ever be lower than expected. Measure the inlet temp of the condenser...then convert to pressures utilizing a pressure/temp chart to determine actual 'high' side pressures. This test is only valid when the system is completely recharged....once more back to the correct equipment.
The reason the system will not accept additional refrigerant....the internal system pressures are equal to the pressures in the refrigerant cylinder. Due to possible internal compressor problems,the compressor no longer is able to lower the suction pressures to allow refrigerant into the system.
Check site sponsor for a good measurement scale and heater blanket to enable a more 'professional' service procedure. They make the job so much easier to accomplish and will reduce initial damage to the compressor due to lack of case lubricant.
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