Subject: xj-digest V1 #2110 From: john meister Date: Sun, 12 Jun 2005 20:09:36 -0700 To: dieseljohn-at-comcast.net xj-digest Wednesday, June 8 2005 Volume 01 : Number 2110 Forum for Discussion of XJ cherokees and wagoneers Brian Colucci Digest Coordinator Contents: Re: xj: function of an AC clutch xj: The Big XJ Chill xj: The Big XJ Chill Re: xj: The Big XJ Chill Re: xj: function of an AC clutch XJ Digest Home Page: http://www.digest.net/jeep/xj/ Send submissions to xj-digest-at-digest.net Send administrative requests to xj-digest-request-at-digest.net To unsubscribe, include the word unsubscribe by itself in the body of the message, unless you are sending the request from a different address than the one that appears on the list. Include the word help in a message to xj-digest-request to get a list of other majordomo commands. ---------------------------------------------------------------------- Date: Tue, 7 Jun 2005 23:06:37 -0500 From: "Mike Petersen" Subject: Re: xj: function of an AC clutch Your AC cycling problem sounds like low suction pressure. Are you sure that you were reading the low side?? Low side pressures on a 134 system should be about 60 to 65 psi and the high side should read about 250. There usually is a suction pressure switch that shuts the compressor off to avoid damage when the charge is low. I did three of these yesterday. Mike - ----- Original Message ----- From: "Marc" To: Sent: Tuesday, June 07, 2005 9:05 PM Subject: Re: xj: function of an AC clutch Ed, I'm sorry I cannot answer you're question. But, I'm curious about the older XJ fix, I have an '89. I have a problem where mine cools for a while and then doesn't. Marc Z. Ed Kummel wrote: > OK. Yesterday was a scorcher out here on the east > coast. My latest acquisition is a 1996 Grand Cherokee > Limited. Nice Jeep (almost not a Jeep though, if you > know what I mean) > We wanted to drive in style with the AC going but > found that it doesn't seem to work quite right. > I remember some discussion about AC stuff on here a > few months ago and perhaps someone may have some > answers for me. > Here is what's happening. > Turn the AC on and set the temperature to a low > setting. The AC clutch will cycle on for about 2 > seconds, then cycle off for about 5 seconds, then on > for 2 seconds, then off for 5 seconds. It will do this > over and over...The low pressure line will get *cool* > but not COLD. I put a pressure gauge on the low > pressure side and when the compressor cycles on, it > reads about 125psi, when the compressor cycles off, > the pressure reads about 130psi. There's refridgerant > (r134a) in the system (I couldn't find the watch glass > to verify, but the pressure's good). I pulled the > relay to check if there's a bad contact, but that's > good too... > So, here's my question. The normal function for a > compressor in a '96 Jeep running r134a coolant. Should > it cycle on and off like that? And if so, why am I not > getting any COLD air? It get's cooler than a 150 > degree car interior, but not COLD. > I remember on the older Jeeps (XJs, I have a 90 and 89 > xj) there was a relay fix that kept the compressor on > continuously...I performed this mod on both Jeeps and > they run colder with this mod. Is there something > similar I need to do with this one too? > > Thanks for the info (in advance) > > Ed > web/gadget guru > > "I'm not an expert, but I *did* stay at a Holiday Inn Express once..." > --Holiday Inn Commercial > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com ------------------------------ Date: Wed, 08 Jun 2005 06:39:17 -0400 From: Colucci B Subject: xj: The Big XJ Chill Greetings To he XJ World! OK I am going to kill to birds with one big stone here and answer the A/C Questions, since I have chased the illusive XJ "ice box" on two different XJ's. First off Ed, your 96 needs a shot of R134a refrigerant. I question the accuracy of your gauge at this point. I would be interested to know what the high pressure reading looks like. Rapid cycling is a sign of low refrigerant level in the system. However if your gauge is right you may have one of two problems. The system may have to much refrigerant in it, and you might need to bleed some off, or you might have a blockage in the system. Which that could get expensive to fix. Have you attempted to jumper the connector going to the clutch directly to the positive terminal on your battery, and then after say 3 - 5 minutes taking a vent temperature reading at your center vent. Of course when doing this you would naturally make sure all of the windows are up, the blower is set to high, and the system is set to max A/C or recirculate. With these answers we can move forward with your troubleshooting process. Now onto Mr. Marc. Electrical systems in a car or truck are designed in a certain way for a reason. I am never a big fan of a short cut alteration to bypass something crucial like a relay. Just do not do it! Now lets get you some cold air. Your system probably is still running R 12 unless it has been converted. I hope for your coolness sake it is still on R 12. R 12 is such a superior refrigerant to the R 134a. For your first test you will need to perform the same test I suggested to Ed. Set your selector to Max A/C, set the blower to high, jumper your clutch line to the positive terminal on the battery, and get a temp reading at the center vent. I'm betting you will get a reading between 35 - 45 degrees. If not then it is time for a charge of refrigerant. I still think you will get the correct temp reading. Here is the thing at this point. You have one of three failures in your system. I will list them from cheapest to most expensive. 1) you need a new A/C relay. 2) you need a new thermostat. Something sticks in my mind Jeep calls it a CTO, but I am working from memory and do not have time to pull shop manuals right now. Anyway this is a switch that is mounted under the dash, on the passenger side, in the plenum box. It actually detects when the system ices up and then shuts down the compressor. When the ice melts the compressor comes back on. 3) Finally your compressor clutch field magnet may be week. This will cause the compressor clutch to shut down after the system has been running for several minutes. After the clutch cools it will usually reenguage. The solution here is to replace the clutch. Here is my experience. I have replaced many perfectly good relays, and CTO switches in an attempt to solve this problem, when in actuality the culprit has always been a failing clutch. The thing that is interesting is that Jeep must have known about the lack of quality in these clutches, because they are actually replaceable independent of the compressor. Expect to spend $245 at your local dealer for a new one. You might find out while doing your jumper test that the clutch will disengage. If this happens your clutch is dead. It can take 15 - 20 minutes for clutch disengagement in this test, but the key is that it will not come back on until after it cools. Now if everything is functioning correctly in your system and you want just a bit more cool air. You can purchase an after market CTO switch from a local automotive A/C house that actually has a potentiometer on it to adjust its sensitivity. I put one in one XJ as a test, before I found the failing clutch, and it does allow you to lower the frost point to give you some additional cool air, while still preserving the integrity of the electrical system. Be advised if you do this you can damage your plenum box, or blower motor by building a large block of ice in the box, if you have the setting to cold. You have been warned!!! Until The Next Dimension, Admiral "Coluch." Starfleet Headquarters Ohio Post End Transmission........................ ------------------------------ Date: Wed, 08 Jun 2005 06:30:39 -0400 From: Colucci B Subject: xj: The Big XJ Chill Greetings To he XJ World! OK I am going to kill to birds with one big stone here and answer the A/C Questions, since I have chased the illusive XJ "ice box" on two different XJ's. First off Ed, your 96 needs a shot of R134a refrigerant. I question the accuracy of your gauge at this point. I would be interested to know what the high pressure reading looks like. Rapid cycling is a sign of low refrigerant level in the system. However if your gauge is right you may have one of two problems. The system may have to much refrigerant in it, and you might need to bleed some off, or you might have a blockage in the system. Which that could get expensive to fix. Have you attempted to jumper the connector going to the clutch directly to the positive terminal on your battery, and then after say 3 - 5 minutes taking a vent temperature reading at your center vent. Of course when doing this you would naturally make sure all of the windows are up, the blower is set to high, and the system is set to max A/C or recirculate. With these answers we can move forward with your troubleshooting process. Now onto Mr. Marc. Electrical systems in a car or truck are designed in a certain way for a reason. I am never a big fan of a short cut alteration to bypass something crucial like a relay. Just do not do it! Now lets get you some cold air. Your system probably is still running R 12 unless it has been converted. I hope for your coolness sake it is still on R 12. R 12 is such a superior refrigerant to the R 134a. For your first test you will need to perform the same test I suggested to Ed. Set your selector to Max A/C, set the blower to high, jumper your clutch line to the positive terminal on the battery, and get a temp reading at the center vent. I'm betting you will get a reading between 35 - 45 degrees. If not then it is time for a charge of refrigerant. I still think you will get the correct temp reading. Here is the thing at this point. You have one of three failures in your system. I will list them from cheapest to most expensive. 1) you need a new A/C relay. 2) you need a new thermostat. Something sticks in my mind Jeep calls it a CTO, but I am working from memory and do not have time to pull shop manuals right now. Anyway this is a switch that is mounted under the dash, on the passenger side, in the plenum box. It actually detects when the system ices up and then shuts down the compressor. When the ice melts the compressor comes back on. 3) Finally your compressor clutch field magnet may be week. This will cause the compressor clutch to shut down after the system has been running for several minutes. After the clutch cools it will usually reenguage. The solution here is to replace the clutch. Here is my experience. I have replaced many perfectly good relays, and CTO switches in an attempt to solve this problem, when in actuality the culprit has always been a failing clutch. The thing that is interesting is that Jeep must have known about the lack of quality in these clutches, because they are actually replaceable independent of the compressor. Expect to spend $245 at your local dealer for a new one. You might find out while doing your jumper test that the clutch will disengage. If this happens your clutch is dead. It can take 15 - 20 minutes for clutch disengagement in this test, but the key is that it will not come back on until after it cools. Now if everything is functioning correctly in your system and you want just a bit more cool air. You can purchase an after market CTO switch from a local automotive A/C house that actually has a potentiometer on it to adjust its sensitivity. I put one in one XJ as a test, before I found the failing clutch, and it does allow you to lower the frost point to give you some additional cool air, while still preserving the integrity of the electrical system. Be advised if you do this you can damage your plenum box, or blower motor by building a large block of ice in the box, if you have the setting to cold. You have been warned!!! Until The Next Dimension, Admiral "Coluch." Starfleet Headquarters Ohio Post End Transmission........................ ------------------------------ Date: Wed, 08 Jun 2005 07:21:36 -0400 From: Marc Subject: Re: xj: The Big XJ Chill Thanks for the information. Based on your evaluation of my AC issue in my '89 XJ, and yes it's running R12, I think that it is the clutch. On cooler days the system runs great. On hot days, it runs for a while and then stops. This matches with your description that it needs to cool. How easy is it to replace the clutch? I'm an average weekend tinkerer. Marc Z. Colucci B wrote: > Greetings To he XJ World! > > OK I am going to kill to birds with one big stone here and answer the A/C Questions, since I have chased the illusive XJ "ice box" on two different XJ's. > > First off Ed, your 96 needs a shot of R134a refrigerant. I question the accuracy of your gauge at this point. I would be interested to know what the high pressure reading looks like. Rapid cycling is a sign of low refrigerant level in the system. However if your gauge is right you may have one of two problems. The system may have to much refrigerant in it, and you might need to bleed some off, or you might have a blockage in the system. Which that could get expensive to fix. Have you attempted to jumper the connector going to the clutch directly to the positive terminal on your battery, and then after say 3 - 5 minutes taking a vent temperature reading at your center vent. Of course when doing this you would naturally make sure all of the windows are up, the blower is set to high, and the system is set to max A/C or recirculate. With these answers we can move forward with your troubleshooting process. > > Now onto Mr. Marc. Electrical systems in a car or truck are designed in a certain way for a reason. I am never a big fan of a short cut alteration to bypass something crucial like a relay. Just do not do it! Now lets get you some cold air. Your system probably is still running R 12 unless it has been converted. I hope for your coolness sake it is still on R 12. R 12 is such a superior refrigerant to the R 134a. For your first test you will need to perform the same test I suggested to Ed. Set your selector to Max A/C, set the blower to high, jumper your clutch line to the positive terminal on the battery, and get a temp reading at the center vent. I'm betting you will get a reading between 35 - 45 degrees. If not then it is time for a charge of refrigerant. I still think you will get the correct temp reading. Here is the thing at this point. You have one of three failures in your system. I will list them from cheapest to most expensive. 1) you need a new A/C relay. 2) you need a new thermostat. Something sticks in my mind Jeep calls it a CTO, but I am working from memory and do not have time to pull shop manuals right now. Anyway this is a switch that is mounted under the dash, on the passenger side, in the plenum box. It actually detects when the system ices up and then shuts down the compressor. When the ice melts the compressor comes back on. 3) Finally your compressor clutch field magnet may be week. This will cause the compressor clutch to shut down after the system has been running for several minutes. After the clutch cools it will usually reenguage. The solution here is to replace the clutch. Here is my experience. I have replaced many perfectly good relays, and CTO switches in an attempt to solve this problem, when in actuality the culprit has always been a failing clutch. The thing that is interesting is that Jeep must have known about the lack of quality in these clutches, because they are actually replaceable independent of the compressor. Expect to spend $245 at your local dealer for a new one. You might find out while doing your jumper test that the clutch will disengage. If this happens your clutch is dead. It can take 15 - 20 minutes for clutch disengagement in this test, but the key is that it will not come back on until after it cools. Now if everything is functioning correctly in your system and you want just a bit more cool air. You can purchase an after market CTO switch from a local automotive A/C house that actually has a potentiometer on it to adjust its sensitivity. I put one in one XJ as a test, before I found the failing clutch, and it does allow you to lower the frost point to give you some additional cool air, while still preserving the integrity of the electrical system. Be advised if you do this you can damage your plenum box, or blower motor by building a large block of ice in the box, if you have the setting to cold. You have been warned!!! > > > Until The Next Dimension, > Admiral "Coluch." > Starfleet Headquarters > Ohio Post > End Transmission........................ ------------------------------ Date: Wed, 8 Jun 2005 07:53:00 -0400 From: "Don Hansen" Subject: Re: xj: function of an AC clutch 30 psi=about 32 degrees. Why 60-65??? - ----- Original Message ----- From: "Mike Petersen" To: Sent: Wednesday, June 08, 2005 12:06 AM Subject: Re: xj: function of an AC clutch > Your AC cycling problem sounds like low suction pressure. Are you sure that > you were reading the low side?? Low side pressures on a 134 system should be > about 60 to 65 psi and the high side should read about 250. > > There usually is a suction pressure switch that shuts the compressor off to > avoid damage when the charge is low. I did three of these yesterday. > > Mike > ----- Original Message ----- From: "Marc" > To: > Sent: Tuesday, June 07, 2005 9:05 PM > Subject: Re: xj: function of an AC clutch > > > Ed, I'm sorry I cannot answer you're question. But, I'm > curious about the older XJ fix, I have an '89. I have a > problem where mine cools for a while and then doesn't. > > Marc Z. > > Ed Kummel wrote: > >> OK. Yesterday was a scorcher out here on the east >> coast. My latest acquisition is a 1996 Grand Cherokee >> Limited. Nice Jeep (almost not a Jeep though, if you >> know what I mean) >> We wanted to drive in style with the AC going but >> found that it doesn't seem to work quite right. >> I remember some discussion about AC stuff on here a >> few months ago and perhaps someone may have some >> answers for me. >> Here is what's happening. >> Turn the AC on and set the temperature to a low >> setting. The AC clutch will cycle on for about 2 >> seconds, then cycle off for about 5 seconds, then on >> for 2 seconds, then off for 5 seconds. It will do this >> over and over...The low pressure line will get *cool* >> but not COLD. I put a pressure gauge on the low >> pressure side and when the compressor cycles on, it >> reads about 125psi, when the compressor cycles off, >> the pressure reads about 130psi. There's refridgerant >> (r134a) in the system (I couldn't find the watch glass >> to verify, but the pressure's good). I pulled the >> relay to check if there's a bad contact, but that's >> good too... >> So, here's my question. The normal function for a >> compressor in a '96 Jeep running r134a coolant. Should >> it cycle on and off like that? And if so, why am I not >> getting any COLD air? It get's cooler than a 150 >> degree car interior, but not COLD. >> I remember on the older Jeeps (XJs, I have a 90 and 89 >> xj) there was a relay fix that kept the compressor on >> continuously...I performed this mod on both Jeeps and >> they run colder with this mod. Is there something >> similar I need to do with this one too? >> >> Thanks for the info (in advance) >> >> Ed >> web/gadget guru >> >> "I'm not an expert, but I *did* stay at a Holiday Inn Express once..." >> --Holiday Inn Commercial >> Tired of spam? Yahoo! Mail has the best spam protection around >> http://mail.yahoo.com ------------------------------ End of xj-digest V1 #2110 *************************