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2G AC Pulsing

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
HI all, when I turn my AC on It pulses about once a second. I feel the pull on the engine with every pulse. Coldish air comes out but it's not cold enough to keep me cool in the southern heat.

I'm sorry if this has been answered before, I've been looking through threads and searching now for 30 minutes but haven't found the answer. I am Gen X so forums and tech comes a little harder for me.

Here is what I have done so far:
1. Checked the connections for anything obvious like exposed wires etc and found nothing.
2. Checked the pressure and added until it was good. Air got cooler but still not cold enough.

I've been blessed in the past with cars that have not had issues with AC any more than slight leaks.

I would appreciate any help or a link to a thread that could help me.
 
Last edited by a moderator:

waltah

Proven Member
319
133
Mar 2, 2011
fairfield, Virginia
Do you have a gauge set or was your 'checked the pressure' with the gauge on a 'DIY add some R-134a to your system' bottle?

Idling with the hood up and the A/C on full and recirc. can you hear the compressor clutch engaging, disengaging in time with those pulses? Engine speed going up and down a little? Fans coming on and going off?

There is a 'sight glass' -- a small round window on the top of the filter/dryer cartridge that's set in the left front fender, visible from above right behind the headlamp and forward of the power steering reservoir. Clean that window and see what you can see when your A/C is on. Does what you see change with the pulses?

You are probably going to need a professional to fix whatever's wrong but maybe we can get an idea from a few simple checks.
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Hey Waltah, thank you very much for answering this post.
I used a guage that is probably in the DIY category that you mentioned. It's a gauge that I bought separate from the bottle that uses the self sealing bottles that thread into it and it was like $50. I've used it on all my other vehicles and it's been working to get me cold AC on most of what I've used it on except the Eclipse but I suspect other issues with this thing.
I'm going to take the rest of the steps you've mentioned and I'll let you know how it goes.
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Hey Waltah, here is an update, sorry it took me so long I've had a lot going on. So first thing I did since it was the last part of my maintenance since buying the car was the accessory belts. The AC belt was absolutely shot so I thought this might have something to do with it. I replaced it and the others. As I was removing the alternator belt I discovered the nut that tightens the lower mount of the alternator was missing. I put a nut on there when I put everything back together. I drove around to see if that took care of anything and I found out that I now have ice cold air but I am still getting the pulsing when I am driving but now it's not all the time. It seems to be when the compressor clutch kicks in that I am getting the pulsing. It pulses about every 2 seconds but you can only notice it while driving, you can't tell while it's idling as the pusling is not a sound, it's a hesitation while driving that you feel almost like a misfire. When the compressor clutch kicks in it seems to be a heavy draw on the system and it drops the idle rpms about 200 - 250 rpm.

I looked through the small sight glass and when the compressor kicks in the and fans are running it looks like white fluid is running through it. When it kicks back off it goes black again. Any ideas?
 

Clipsoe

Proven Member
100
23
Apr 22, 2015
Fort Lauderdale, Florida
The way it sounds is like it has freon, but might might be low, or too much. There is a high pressure switch and low pressure switch that stops the compressor if the pressure is too high/ low. While it is pulsing does it stay blowing cold? Listen to the compressor and see if it engaging/ disengaging continuously.
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
The pressure is showing in the green. I get the pulsing only when I'm in gear and I don't hear any clicks during the pulses. This is how a drive goes. I start off and everything is normal for about 1-2 minutes. Then I get another 1 - 2 minutes of driving where every two seconds I get the pulsing, then it stops and I get another 1-2 minutes of driving that's perfectly fine. While it's pulsing I get cold air, I think it's a little colder during the pulsing then it is while it's not pulsing. I've not heard the compressor engaging and disengaging very frequently, only every couple minutes.
 

Sirius1995

Proven Member
118
19
Jun 15, 2021
Hattiesburg, Mississippi
Sirius, you mentioned the AC switch and magnet clutch, how did you come up with that?
According what you told, there's not that many components for a either, not so long time ago I had same problem
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Cool, so I've got a parts car with a switch in it so I'll throw that in and see what happens. As for the clutch, is there a decent one to buy out there or should I just buy the whole compressor. From what I'm reading here on the forums most people recommend replacing the whole compressor.
 

Clipsoe

Proven Member
100
23
Apr 22, 2015
Fort Lauderdale, Florida
Yea, buying the compressor would probably be best bet, but will require some extra work. If you have just the DIY gauge, and you're gonna change the compressor then you're either gonna have to take it to a shop to remove the freon (should be cheaper to have them remove it into their tank to put it back in instead of wasting into the air), and once the new compressor is in take it back to vacuum and recharge the ac, or buy/rent a pro ac gauge set with vacuum pump and proper amount of freon.

 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
So my brain has been thinking it's the compressor this whole time but I hate to throw parts at a problem so I'm just trying to narrow down by eliminating anything else it could be. So in various forums and online etc. the IACV comes up as a possible culprit. I have had some intermittent idle issues which I was thinking was actually the FIAV. After the car warms up, sometimes I get crazy idle speeds like 2000 to 3000 but sometimes it's fine. Lately it's been fine and I can't identify any correlation between AC pulsing and fast idle. I was also wondering if doing some data logging on Torque would help me to figure anything out but I can't really identify what parameters I would log to tell me anything. Does anyone else think I should do any more tests before buying a compressor?
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
The throttle body is sparkling clean because I did the shaft seals and the gaskets and o ring recently but I never did clean off the IACV. I just pulled it and cleaned it out and put it back in. When I started it up afterward I did notice that when I turned on the AC it clicked on and off several times before staying on and then cycling normally. Once it was cycling normally I noticed that I was getting a loud mechanical noise from the compressor area. I could also hear it from the wheel well on the side of the compressor so I think it's safe to say that it's time to replace it. If anyone else has recommendations on a good one I would appreciate it. Also, should I replace anything else along with it while I'm doing the work?
 

CKOPOCT

Proven Member
61
36
May 27, 2017
North East, Maryland
Yes. Replace the receiver dryer. Also, in case you are not aware, evacuate the system after you put everything back together. Why? Drawing the system down to a vacuum boils off any moisture in the lines, moisture that entered when you took the lines off to replace the compressor. If you don't evacuate the system you risk that moisture both corroding the system and crystalline in the evap case lines causing blockage and failure.
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Thanks man. I'm ordering the vacuum pump and manifold gauges now. What do you think about the expansion valve? Do I need to change it as well? I'd rather not get into the evap box.
 

waltah

Proven Member
319
133
Mar 2, 2011
fairfield, Virginia
I would now take this car to an A/C shop and get them to diagnose it. You are setting out to do 'Auto Air Conditioning 101 Self-Taught' and while there's nothing wrong with that, it's going to be time consuming, about as expensive as having a shop do the job, and with an uncertain result.

It sounds like something is causing the clutch to engage/disengage too frequently or perhaps slip sometimes. There are probably not many ways for that to happen and an experienced A/C tech is likely to finger what's wrong pretty quickly.

The combination of mechanical noise you heard and the feeling of a heavy load pulsing makes me wonder about way too much oil in the system. All these cars have now been worked on by everyone and his uncle with ??? skill level and there's just no telling what's in there.
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Hey Waltah, thanks for the info. You are certainly correct that I would be engaging in self taught AC as would be the case in just about everything I've done mechanically since I started working on cars. Sometimes I've made some bonehead mistakes (like the time I didn't fully close my BMW's hood before I took a drive, you can guess how that ended). Most of my mistakes have led me to learn that proper diagnosis will save me time and money and I think that's where you are going with this. Where I differ in your opinion is only that I want to be the one to do the proper diagnosis instead of leaving it to a shop because even though in the last 10 years this is the first time I've had to do anything with ac other than recharging I know it's bound to happen again. I'm ordering the manifold gauges now, I would love to use them to do some more diagnosis before pulling the compressor and am certainly open to ideas as to what tests to do.
 

dwb

Proven Member
170
65
Sep 9, 2021
Broomfield, Colorado
If your compressor is cycling off and on (compressor clutch engaging and disengaging) it's likely due to an over filled system or something restricting the flow of refrigerant, like too much oil like @waltah mentioned. In my experience, it blows cold for a few minutes, then the compressor starts to cycle off and on as pressures climb and drop. Alternatively it may be a faulty high pressure switch. I'm not sure where that's at on a 2g, but on a 1g it's right next to the sight glass. You can short this 2-prong connector and see if that's what's causing it to cycle, but be careful as you don't want to build too much pressure. This is a safety switch. Best to try with a gauge set attached.

Not sure if you have already purchased a vacuum pump and gauge set, but I was able to borrow those from my local O'reilly's.
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Thanks for the info man. After having driven it so many times I can confirm that the pulsing is not the clutch engaging and disengaging because thankfully this makes a pretty loud sound. The pulsing is happening while the clutch is engaged. When the clutch disengages, the car drives normally. Before I changed the AC belt, I still had the pulsing but I had warmish air coming out. After I changed the belt I have good cold air coming out but I still have the pulsing. So the only thing I know for sure is that it has something to do with the compressor as the compressor is directly connected by a belt to the crank pulley and the only thing that could cause the car to jerk every time it pulses would be some kind of binding which makes it harder for the engine to move the crank pulley. I suspect the mechanical noise to be the bearings in the compressor pulley as I hear the noise whether the clutch is engaged or not unless it's the bearings in the tensioner pulley. I would assume that the pulsing in the AC however may have caused damage to the bearings in either one or both pulleys as that kind of forced jerking can't be good for them. You just gave a great idea about loaning the tools from Oreillys, I need to take them back their steering wheel puller anyway. I'll hook up the gauges and see if they tell us anything.
 

waltah

Proven Member
319
133
Mar 2, 2011
fairfield, Virginia
You are certainly correct that I would be engaging in self taught AC as would be the case in just about everything I've done mechanically since I started working on cars. Sometimes I've made some bonehead mistakes (like the time I didn't fully close my BMW's hood before I took a drive, you can guess how that ended). Most of my mistakes have led me to learn that proper diagnosis will save me time and money and I think that's where you are going with this. Where I differ in your opinion is only that I want to be the one to do the proper diagnosis instead of leaving it to a shop because even though in the last 10 years this is the first time I've had to do anything with ac other than recharging I know it's bound to happen again.
That's pretty much where I come from too --- I'll do it just for the learning or because the question is interesting. It's also true that where I live it's pretty much an auto mech desert: You can get brake shoes replaced, or ball joints but much more than that you're risking your car. So -- if you want to DIY, go for it!

As to mistakes: Have you ever put on a cam sprocket finger tight and taken your car for a test drive? Yeah, I thought not. The answers to your first two questions are "About a mile" and "a whole bunch of bent valves."

After having driven it so many times I can confirm that the pulsing is not the clutch engaging and disengaging because thankfully this makes a pretty loud sound. The pulsing is happening while the clutch is engaged. When the clutch disengages, the car drives normally. Before I changed the AC belt, I still had the pulsing but I had warmish air coming out. After I changed the belt I have good cold air coming out but I still have the pulsing. So the only thing I know for sure is that it has something to do with the compressor as the compressor is directly connected by a belt to the crank pulley and the only thing that could cause the car to jerk every time it pulses would be some kind of binding which makes it harder for the engine to move the crank pulley. I suspect the mechanical noise to be the bearings in the compressor pulley as I hear the noise whether the clutch is engaged or not unless it's the bearings in the tensioner pulley. I would assume that the pulsing in the AC however may have caused damage to the bearings in either one or both pulleys as that kind of forced jerking can't be good for them.
Our cars have scroll-type compressors. Unless the compressor is internally damaged so it binds about the only thing I can think of that would cause this pulsing is slugs of oil passing through because there is way too much oil -- the amount is fairly critical -- or possibly some or all of the oil is the wrong kind and doesn't disperse in the refrigerant and get carried along like a fog.

If you take this to the right A/C mechanic he should recognize the symptom. I've done maybe 10 complete A/C overhauls and I've never seen it but someone who has done 20 jobs a week for a few years -- he prob'ly has. Can you find that guy? I have no clue.

If this were my car and I were determined to DIY just as a learning experience I would probably rent the tools for the first such job (gauges and vacuum pump), give myself a week, and tear out the whole system. Flush all the lines and the condenser -- you can get an A/C flush solvent at auto parts stores though you may have to ask for it, get a couple of cans. You will need shop air (75 PSI or more and lots of CFM) to blow out the solvent and the oil.

The evaporator on these cars is a real pig to take out; for a start I'd leave it alone. Take out the compressor though -- that's not easy but the symptoms fit compressor issues so you can't skip it.

The compressor does not get solvent flushed. Instead once you have it out turn it so the connections are down and rotate it clockwise (forward) enough turns that you get no more oil out. Put paper towels under so you can look at the oil you get. If what comes out is completely free of particles and the compressor turns freely by hand (clutch plate at the center -- not just the pulley) then keep it. If there are particles or any binding, it's trash: Buy a new one.

If particles come out then you should buy a new condenser too: From about '95 on the passages are so small that it's very hard to get all the trash out and not worth risking contaminating everything else and not having good cooling 'cause it's partly plugged.

Also if you get particles out you must pull the evaporator and disassemble and replace its insides.

Regardless of everything else buy a new dryer cartridge. That's a nuisance to change on these cars but not actually hard. Leave this sealed until you actually have in hand the lines to connect to it and the rest of the system is hooked up -- it's job is to absorb leftover moisture in the system and if it's exposed to air it'll suck that moisture instead.

With everything either washed out or known to be clean, reassemble, new O-rings everywhere. Note that all the joints are doweled so you have to align the parts correctly and be sure they completely engage: You cannot use the bolts to pull a joint closed --- if you can't push it by hand, 'sum ting wong' and you have to fix it. (Otherwise you will at best have a leak there.) Bolts should be tight enough to not vibrate loose and not more -- the O-rings do the sealing and overtightening a bolt can easily lead to a cracked fitting (leak) or a stripped thread. Hook up the pump and pull a vacuum. It should get near 30" in five minutes but keep the vacuum on for an hour or so. Then turn off the pump: It should hold almost without change for 5-10 minutes.

At that point you're ready to charge; We'll talk about that when you get there.

There are lots of details for the above work: I outlined the whole thing so you can see the size of the learning experience. The rational answer is to find a Pro but since I'm often irrational about these things I'm not going to give you a hard time if you are the same.

Step 1. Get the gauges, hook 'em up, and report pressures. GET SAFETY GLASSES AND GLOVES and wear them anytime you will be working on a live system. If you haven't used A/C gauges before get instructions for that -- it's not quite as simple as 'hook 'em on.'
 

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Hey Waltah, thanks for the info. Here is what I have done so far. I got the manifold gauges and hooked them up and the reading is way off. I have High pressure on the low pressure side and low pressure on the high side. I am uploading a video. So Something is definitely not right. Today I was getting warm air from the vents and the compressor kicked on and never kicked back off.
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kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Actually, I think it was the opposite, the compressor tried to turn on but turned back off and never came back on which is at least partly why my reading is so off. I tried for a few minutes several times to get it to kick on but got nothing. Is this the final nail in the coffin of my compressor or something else I should check on?
 

waltah

Proven Member
319
133
Mar 2, 2011
fairfield, Virginia
The first question is why the pressures are backward. The blue (low side) hose should go down to the compressor. The red (high side) hose and coupler should be on the fitting on the left fender well. The valves at the gauges should be all the way off. Most gauge sets have knobs on the couplers: Those are turned all the way left when connecting and disconnecting; After connecting you turn the knobs on the couplers all the way to the right to depress (open) the Schraeder valves in the service ports.

That's the setup to check pressures.

There can be several reasons for the compressor not to start. The compressor itself isn't too likely to be one of them unless it's frozen; that would likely give you a broken or at least smoking belt.
 
Last edited:

kingje1

Proven Member
60
14
Feb 27, 2022
Nashville, Tennessee
Here's an update. I started driving around and got the compressor to come on finally and the car was pulsing but this time was different. The pulsing was stronger, like it was binding up more and this time there was a noise. I stopped in the middle of my street and took a recording.
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