Chris Posted August 3, 2005 Report Share Posted August 3, 2005 Hey everyone, I just had my AC converted to R-134a yesterday. The AC had never worked since I bought the car. Blows nice cold air and the rad fans run, everything seemed good until I hit the highway. Every 30 seconds or so, there is a small surge while cruising. I think it must be the compressor kicking on/off, as it doesnt surge in ECON mode. That being said, if I set the climate control to 16º and have the windows open (ambient 24º) the surging still happens. Shouldn't the compressor be running solid? My right rad fan burned itself out last week so I am running with only the left rad fan. The AC rad is on the front right and gets red hot (but it should be cooled at highway speeds, no??). I will be replacing the fan motor over the next few days, but I dont really think it will solve the surging. Do you guys have any other suggestions? The car ran fine until the AC was changed over. Thanks -Chris Link to comment Share on other sites More sharing options...
bigjayzway Posted August 3, 2005 Report Share Posted August 3, 2005 Change the fan as soon as you can! The AC rad is on the front right and gets red hot (but it should be cooled at highway speeds, no??). NO!!!! Absolutely not! In fact I would not run the car till I did change the fan if this is the case! Big Jay Life is too short to grow up! Link to comment Share on other sites More sharing options...
Chris Posted August 4, 2005 Author Report Share Posted August 4, 2005 Just to clarify, it is the AC rad that is hot, and even if the right fan (located on the other side of the 'normal' rad) was working, it would have little cooling effect on the AC rad (??) I'm not worried about running the car with no right fan as they only come on a few times per year (engine rarely gets past 210º F). -Chris Link to comment Share on other sites More sharing options...
brmurph Posted August 5, 2005 Report Share Posted August 5, 2005 Can't help you with an answer but can only say that I recently had my compressor replaced by the dealer and I also feal the surging when it cycles on/off. I only notice it when on the interstate usually with the cruse on. It seems it might be a little better now (after about 3000 miles of heavy AC use) but it still bothers me. So hope you find an answer. Link to comment Share on other sites More sharing options...
raz Posted August 5, 2005 Report Share Posted August 5, 2005 Hi all I am a a/c guy and it sounds like you are low on freon. The faster you drive the more rpm's on the compressor which in turn lowers the suction pressure, now their is a low pressure cut out that will cut the compressor off if the pressure gets to low (low charge).When the compressor shuts off the pressure rises or equalizes (high and low side pressures) then the comp. comes back on and it will keep repeating this cycle. Some call this hunting ( low freon). If you are idling or or at low speeds the comp. will run normal. Link to comment Share on other sites More sharing options...
Julio Posted August 5, 2005 Report Share Posted August 5, 2005 Raz is right it will get bad enough that you'll need to reset the computer to turn it back on. Once the pressure diff is critical to the sensors it shuts down. If there is dirt in the system clogging the orifice it will stay off untill it is changed. Both fans should run when I put min toghter I had a cable disconnect off of the pass side fan. Mine ran hot until I recoginized only one fan was running. You need to fix that. Julio Link to comment Share on other sites More sharing options...
STS Posted August 5, 2005 Report Share Posted August 5, 2005 My 97 STS has done this always also, and I think it sucks that a car that originally sold for 45K plus has a noticeable feel when the compressor kicks in and out on the highway. If you can't feel it in your STS then you are not in tune with your car. It is slight but none the less noticable. It should not do it at all, but I think Caddy mis-sized something and figures most people will not notice. I still am happy to put up with it for the luxury of having air conditioning on hot days. If you run in Drive instead of overdrive the rpm's are a little higher and it is less noticeable. I normally turn the AC off so the compressor is not running all the time. Link to comment Share on other sites More sharing options...
Scotty Posted August 5, 2005 Report Share Posted August 5, 2005 My 97 STS has done this always also, and I think it sucks that a car that originally sold for 45K plus has a noticeable feel when the compressor kicks in and out on the highway. If you can't feel it in your STS then you are not in tune with your car. It is slight but none the less noticable. It should not do it at all, but I think Caddy mis-sized something and figures most people will not notice. I still am happy to put up with it for the luxury of having air conditioning on hot days. If you run in Drive instead of overdrive the rpm's are a little higher and it is less noticeable. I normally turn the AC off so the compressor is not running all the time. I have not noticed this engagement since I replaced my compressor last month. I used to feel it on my 91 4.9 Seville more Link to comment Share on other sites More sharing options...
Bob D Posted August 5, 2005 Report Share Posted August 5, 2005 My 97 STS has done this always also, and I think it sucks that a car that originally sold for 45K plus has a noticeable feel when the compressor kicks in and out on the highway. If you can't feel it in your STS then you are not in tune with your car. It is slight but none the less noticable. I've owned over 70 cars by now, and driven many more. Most of them high performance types with lots of options. Given that, and almost 40 years of driving experience, I'd like to think I'm "in tune" with my rides... My. '93, and 2000 STS's give no indication when the A/C kicks in. I was actually quite impressed at the low drag coefficient in the compressor design, compared to many others. Something else is going on... '93 STS.. opened, dropped, wide...fast. Link to comment Share on other sites More sharing options...
STS Posted August 5, 2005 Report Share Posted August 5, 2005 My 97 STS has done this always also, and I think it sucks that a car that originally sold for 45K plus has a noticeable feel when the compressor kicks in and out on the highway. If you can't feel it in your STS then you are not in tune with your car. It is slight but none the less noticable. I've owned over 70 cars by now, and driven many more. Most of them high performance types with lots of options. Given that, and almost 40 years of driving experience, I'd like to think I'm "in tune" with my rides... My. '93, and 2000 STS's give no indication when the A/C kicks in. I was actually quite impressed at the low drag coefficient in the compressor design, compared to many others. Something else is going on... Well, I have not owned 70 cars, but probably 20 or so, and If they had air conditioning I could tell you when any one of them turns on or off. Maybe I am just more in touch with my vehicles than you are. All I am saying is that for a cadillac it should be much less noticeable than it is. Oh, by the way, my wife can't really tell when the compressor kicks on and off either so don't feel bad. Link to comment Share on other sites More sharing options...
davedog Posted August 5, 2005 Report Share Posted August 5, 2005 92 eldo w/78k...AC blows COLD, but has never been officially converted. I can't feel it kick on or off at all. Hope this helps. -dave Crystal Red Tintcoat Exterior | Shale/Brownstone Interior | 32k Link to comment Share on other sites More sharing options...
Bob D Posted August 5, 2005 Report Share Posted August 5, 2005 Maybe I am just more in touch with my vehicles than you are. '93 STS.. opened, dropped, wide...fast. Link to comment Share on other sites More sharing options...
KHE Posted August 5, 2005 Report Share Posted August 5, 2005 All I am saying is that for a cadillac it should be much less noticeable than it is. Oh, by the way, my wife can't really tell when the compressor kicks on and off either so don't feel bad. When the A/C compressor clutch engages, there is an instantaneous load on the engine. It is very slight and most people do not even notice it. If it is as bad as you say, perhaps the bearings in your compressor are on the way out... GM and most other automakers have used cycling clutch orifice tube A/C systems for years. The reason is they are simple and they use less fuel compared to an expansion valve system. The old expansion valve systems would run the compressor constantly and vary the orifice opening at the evaporator to provide a constant pressure. You wouldn't notice anything with the old expansion valve systems except a loss of 2-3 MPG... Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Scotty Posted August 5, 2005 Report Share Posted August 5, 2005 Maybe I am just more in touch with my vehicles than you are. Bob get that gut tuned will you! You are not feeling the force Jedi! Personally I think its an indication that the Hub Bearing is going! Link to comment Share on other sites More sharing options...
Bob D Posted August 5, 2005 Report Share Posted August 5, 2005 Maybe I am just more in touch with my vehicles than you are. Bob get that gut tuned will you! You are not feeling the force Jedi! Personally I think its an indication that the Hub Bearing is going! Like I said... '93 STS.. opened, dropped, wide...fast. Link to comment Share on other sites More sharing options...
STS Posted August 5, 2005 Report Share Posted August 5, 2005 All I am saying is that for a cadillac it should be much less noticeable than it is. Oh, by the way, my wife can't really tell when the compressor kicks on and off either so don't feel bad. When the A/C compressor clutch engages, there is an instantaneous load on the engine. It is very slight and most people do not even notice it. If it is as bad as you say, perhaps the bearings in your compressor are on the way out... GM and most other automakers have used cycling clutch orifice tube A/C systems for years. The reason is they are simple and they use less fuel compared to an expansion valve system. The old expansion valve systems would run the compressor constantly and vary the orifice opening at the evaporator to provide a constant pressure. You wouldn't notice anything with the old expansion valve systems except a loss of 2-3 MPG... That is interesting, I did not realize that years ago they ran the compressor all the time. As far back as I can remember they always cycled the clutch on the compressor. I am not saying that my vehicle is that bad, I am just saying it is noticeable and in the original post the guy said that he can notice it and I am agreeing 100%. It is very noticeable and annoying to me. I am picky that way though, I don't like rotors that are even slightly warped or an alignment that is off, or tires that are not perfectly balanced etc, etc. I like running straight down the highway with my AC on and not feel the compressor, and if I have to get hard on the brakes I don't want any high speed shimmy either. Link to comment Share on other sites More sharing options...
Scotty Posted August 5, 2005 Report Share Posted August 5, 2005 All I am saying is that for a cadillac it should be much less noticeable than it is. Oh, by the way, my wife can't really tell when the compressor kicks on and off either so don't feel bad. When the A/C compressor clutch engages, there is an instantaneous load on the engine. It is very slight and most people do not even notice it. If it is as bad as you say, perhaps the bearings in your compressor are on the way out... GM and most other automakers have used cycling clutch orifice tube A/C systems for years. The reason is they are simple and they use less fuel compared to an expansion valve system. The old expansion valve systems would run the compressor constantly and vary the orifice opening at the evaporator to provide a constant pressure. You wouldn't notice anything with the old expansion valve systems except a loss of 2-3 MPG... That is interesting, I did not realize that years ago they ran the compressor all the time. As far back as I can remember they always cycled the clutch on the compressor. I am not saying that my vehicle is that bad, I am just saying it is noticeable and in the original post the guy said that he can notice it and I am agreeing 100%. It is very noticeable and annoying to me. I am picky that way though, I don't like rotors that are even slightly warped or an alignment that is off, or tires that are not perfectly balanced etc, etc. I like running straight down the highway with my AC on and not feel the compressor, and if I have to get hard on the brakes I don't want any high speed shimmy either. No one is pickier than me, you can be sure. I just drove a 400 mile trip up to the Catskill Mountains in OVERDRIVE at times with the engine seriously laboring (I did not want to gun it up heavy inclines with it packed to the gills with weight) and never once felt the engagement. BUT as I said, I just replaced my compressor hub bearing. I can tell you this, and if you do a search you will find my complain about it, BEFORE I did my hub bearing I DID feel the compressor kick in. I have a 96 YOU have a 97. It took my hub bearing about 18 months to self destruct but looking back on it, I had hints, the engagement was one of them! And yes compressors ran 100% of the time on my old Caddys. Link to comment Share on other sites More sharing options...
STS Posted August 5, 2005 Report Share Posted August 5, 2005 All I am saying is that for a cadillac it should be much less noticeable than it is. Oh, by the way, my wife can't really tell when the compressor kicks on and off either so don't feel bad. When the A/C compressor clutch engages, there is an instantaneous load on the engine. It is very slight and most people do not even notice it. If it is as bad as you say, perhaps the bearings in your compressor are on the way out... GM and most other automakers have used cycling clutch orifice tube A/C systems for years. The reason is they are simple and they use less fuel compared to an expansion valve system. The old expansion valve systems would run the compressor constantly and vary the orifice opening at the evaporator to provide a constant pressure. You wouldn't notice anything with the old expansion valve systems except a loss of 2-3 MPG... That is interesting, I did not realize that years ago they ran the compressor all the time. As far back as I can remember they always cycled the clutch on the compressor. I am not saying that my vehicle is that bad, I am just saying it is noticeable and in the original post the guy said that he can notice it and I am agreeing 100%. It is very noticeable and annoying to me. I am picky that way though, I don't like rotors that are even slightly warped or an alignment that is off, or tires that are not perfectly balanced etc, etc. I like running straight down the highway with my AC on and not feel the compressor, and if I have to get hard on the brakes I don't want any high speed shimmy either. No one is pickier than me, you can be sure. I just drove a 400 mile trip up to the Catskill Mountains in OVERDRIVE at times with the engine seriously laboring (I did not want to gun it up heavy inclines with it packed to the gills with weight) and never once felt the engagement. BUT as I said, I just replaced my compressor hub bearing. I can tell you this, and if you do a search you will find my complain about it, BEFORE I did my hub bearing I DID feel the compressor kick in. I have a 96 YOU have a 97. It took my hub bearing about 18 months to self destruct but looking back on it, I had hints, the engagement was one of them! And yes compressors ran 100% of the time on my old Caddys. What did that cost you to have that bearing replaced? I did have a 93 STS years ago and the air conditioning compressor crapped out around 70k and it cost me something like $700 to replace. I guess it is possible this bearing is going out. Link to comment Share on other sites More sharing options...
Scotty Posted August 5, 2005 Report Share Posted August 5, 2005 The engagement you are feeling should be very subtle at the most very subtle. Sorry, I just noticed above that I said I replaced my hub bearing assembly, I replaced the entire compressor! Sorry! I let mine go too long and burned out my bearing and compressor clutch and had to replace the compressor. The car was NEW to me and I did not know that the AC compressor was NOT suppose to sound that BAD! It sounded like an EGG BEATER Take off the inspection covers and drive the car (not in the rain) and when you return from a ride carefully look over the hub for overheating. Do you have an egg beater sound coming from it? Take off the serp belt and grab the hub and see if it rocks at all. If you have any noise from your compressor at all its a hint something is not right, mine is now quiet. I did the work myself, and it was still expensive to do, but I replaced the compressor, condenser, accumulator, orifice tube, idler wheel, tensioner, serp belt and a few sensors. If you can determine that your hub bearing is starting to go, you can replace JUST the hub before it ruins 1) your seal and 2) your clutch windings from overheating them and melting them, at that point you blow a fuse that controls the cooling fans and AC clutch because the windings short out. Mike Link to comment Share on other sites More sharing options...
dpsq Posted August 5, 2005 Report Share Posted August 5, 2005 I have a 99 STS when I got it, I noticed the freeway surging, which was accompanied by a slight but audible chirp. Since my car was under the extended warranty at the time, I complained to the dealer and they replaced the compressor. since the replacement, I cannot detect the compressor engagement at all. Link to comment Share on other sites More sharing options...
Scotty Posted August 5, 2005 Report Share Posted August 5, 2005 I have a 99 STS when I got it, I noticed the freeway surging, which was accompanied by a slight but audible chirp. Since my car was under the extended warranty at the time, I complained to the dealer and they replaced the compressor. since the replacement, I cannot detect the compressor engagement at all. Thanks for sharing your experience, dpsq Link to comment Share on other sites More sharing options...
Regis Posted August 6, 2005 Report Share Posted August 6, 2005 Ahhh yes, being in tune with one's car......Become one with the car Grasshopper. Not a topic I'd personally want to engage BobD in. I've seen the rough list of cars he's owned plus the description of the terrain he tends to favor. But I'm sure many caddy owners have a keen "Jedi Force". I just had a nice conversation yesterday with an older (late 60s- early 70s) woman that was driving an 04 STS. With kid like excitement in her eyes, she remarked how much power it had, how tight it was in the turns, and very responsive...."I can really feel the road.....I love this STS!" All the while gripping an imaginary steering wheel, leaning side to side, and working that imaginary gas peddle. Such an unlikely person but I'm betting she knows how to use "The Force" LOL When driving around town or just generally driving slow I can barely notice the ac compressor kicking on and off. Of course I can tell because I hear it and feel it through the steering wheel and the peddles......I'm just in tune.... right? Now at highway speeds it is more noticeable, especially if the cruise control is engaged. Seems normal to me once again. Most cars I've driven or rented (many) have done this. I'm really not qualified to get into the specifics as to why this is so I won't. I think Kevin explained why this happens already. I tend to think of it like an outboard motor. If the engine surges while at low speeds one can hardly feel it. There are many factors and variables that absorb the feel of the surge. Now if you're at full throttle and you get that same surge you will definitely feel it. Same surge but different variables at play. "Burns" rubber " I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. " Link to comment Share on other sites More sharing options...
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