A/C Behavior

[suprunner]

Hi all, 

'98 OBW, 2.5L high compression build, 5MT

After moving to Las Vegas, Nevada about two years ago, I've finally begun wanting to use my air conditioning system. Before moving down here, I had a mechanic pull vacuum on the system and charge it. I think he put in less than 2 lbs? It was a very minimal amount. Here are the symptoms that I'm experiencing. Blows cold while driving, and cool while idling. While driving, when the A/C compressor kicks on, there is a VERY noticeable decrease in performance... almost like I've instantaneously been loaded with a 700 lb 4x8 U-Haul trailer...It'll buck/shake the car slightly. I know I've read multiple times on the forum that the A/C can rob power, but this seems exceptional. The motor has good compression (in the 200s) and has lots of power when not using A/C. I am in the habit of turning the A/C off when accelerating from stops. With this amount of strain placed on the motor though, why doesn't it just stall out when idling? The motor doesn't stumble or strain when cycling the A/C on/off while idling. What's the deal? I've checked the gap on the clutch, and it seems to be within specifications. It also appears that this clutch isn't replaceable? I've looked at the different write-ups on this forum, and the videos available, but NONE of them show the type of compressor that mine has... The Triangle with the 3 circular pieces and the single bolt in the center... I've attached the pressure gauge from one of those auto-store recharge kits, and supposedly the system is topped-off. Does this have anything to do with my neutral switch? I've checked my Short Term/Long term fuel trims while idling and I think I don't have a vacuum leak, as they're in the negatives. I'm just worried that I'm going to jump timing because of the instantaneous loading that is presenting, or the A/C is going to catabolize itself while driving and having to replace EVERY part of the system. 

 

Thanks for your time,

 

Greg

[el_freddo]

When driving at speed and the AC compressor is engaged you shouldn’t really feel it too much if at all in a modern vehicle.

With that said, the compressor is going from a standstill to pretty much instantaneously spinning at the speed of the fan belt. That could be enough to feel but it should subside quickly rather than feeling underpowered from there on until the compressor turns off again.

Do you have a lightened flywheel?

Cheers

Bennie

Edited June 21, 2021 by el_freddo

[suprunner]

1 hour ago, el_freddo said:

When driving at speed and the AC compressor is engaged you shouldn’t really feel it too much if at all in a modern vehicle.

With that said, the compressor is going from a standstill to pretty much instantaneously spinning at the speed of the fan belt. That could be enough to feel but it should subside quickly rather than feeling underpowered from there on until the compressor turns off again.

Do you have a lightened flywheel?

Cheers

Bennie

I do have a light-weight flywheel installed. I do have a brand new stock flywheel. Will that take care of this? 

 

Thank you,

Greg

[nvu]

I have a 98 OBS, it's the impreza version 2.5l sohc slightly higher compression frankenmotor,  but likely same ac system.  The initial kick in sometimes makes a squeak noise, but engine doesn't even flinch in power.  Doubt it's the flywheel.  If you're in gear already all the weight of the drivetrain plus pulling the vehicle is a bit bigger than just a 10lb lighter flywheel.

It's probably more electrical and sensors than physical.  If you want to make sure, just loosen the ac belt so it lightly grips the pulley.  Next time the ac kicks in if it really is the pump seizing up, the belt would make slipping noises and you'd lose less power.  Doubt it though, compressor pumps either work or make horrible noises before seizing up.

I'm just guessing at this point, I don't know either, but could an overcharged system do this?  Also if the clutch is somehow shorted out, would the coils pull so much amps it makes the electrics go haywire?

[suprunner]

32 minutes ago, nvu said:

I have a 98 OBS, it's the impreza version 2.5l sohc slightly higher compression frankenmotor,  but likely same ac system.  The initial kick in sometimes makes a squeak noise, but engine doesn't even flinch in power.  Doubt it's the flywheel.  If you're in gear already all the weight of the drivetrain plus pulling the vehicle is a bit bigger than just a 10lb lighter flywheel.

It's probably more electrical and sensors than physical.  If you want to make sure, just loosen the ac belt so it lightly grips the pulley.  Next time the ac kicks in if it really is the pump seizing up, the belt would make slipping noises and you'd lose less power.  Doubt it though, compressor pumps either work or make horrible noises before seizing up.

I'm just guessing at this point, I don't know either, but could an overcharged system do this?  Also if the clutch is somehow shorted out, would the coils pull so much amps it makes the electrics go haywire?

okay, thank you. I'll try that tomorrow. 

[1 Lucky Texan]

I have read several times that the H tube or orifice w'ever can make a 'hooting' noise in an overcharged system.

[suprunner]

1 hour ago, 1 Lucky Texan said:

I have read several times that the H tube or orifice w'ever can make a 'hooting' noise in an overcharged system.

The only thing that I hear is in the cab. When driving I hear the relay under the dash operating (kinda often, maybe every minute or two sometimes more) and the sound of compressing gasses under the dash on the passenger side. With the hood up standing in front of the car while idling, the AC doesn't make any unusual noises. I'll search the forum for threads with the hooting to see if there is a commonality to my situation. 

Thanks!

 

Greg

[idosubaru]

I doubt it’s flywheel as well. I’ve repaired and charged dozens of no working unknown Subaru AC systems. They seem simple and robust with few issues and very forgiving.  I don’t pull vacuums and haven’t dusted off my professional grade gauges or remember where my vacuum puller is in over a decade because Subarus are so simple and easy and don’t need them.

Compressor may need replaced?  If it’s turning on but not cooling it seems like it almost has to be wrong charge or bad ac unit.  What else could it be?

Compressor is only failure I’ve seen...though I’m sure there are others. Ive always just installed used Subaru compressors and never had an issue doing that. And they’re usually like $30-$50, cheap and easy to replace. 

Subaru only take roughly a little over 20 ounces. Like 21 or 22.  I don’t even pull a vacuum and it works fine in our miserable 90 degree 90% humidity summers  

 

Edited June 22, 2021 by idosubaru

[1 Lucky Texan]

yep, 22oz for the outback, I think my WRX is less, maybe around 18???

[idosubaru]

How sure are you the charge volume is correct?  A little low or high will cause poor output at specific conditions.

When it’s running at idle how much is the ac compressor cycling on and off?

[1 Lucky Texan]

is there a lot of red stain/debris on the hood above and parts near the compressor? that could indicate the clutch slipping.

[suprunner]

On 6/22/2021 at 6:20 PM, idosubaru said:

How sure are you the charge volume is correct?  A little low or high will cause poor output at specific conditions.

When it’s running at idle how much is the ac compressor cycling on and off?

Running at idle, it seems to come on about once every 10 seconds. The dragging is certainly worse when we are above 100 degrees down here. This morning it was barely noticeable when driving, but it was probably only upper 80s; we just got some much needed moisture. It went back to "normal" as the day got hotter. 

[suprunner]

On 6/23/2021 at 11:49 AM, 1 Lucky Texan said:

is there a lot of red stain/debris on the hood above and parts near the compressor? that could indicate the clutch slipping.

None that I can see. 

[suprunner]

On 6/21/2021 at 8:26 PM, nvu said:

I have a 98 OBS, it's the impreza version 2.5l sohc slightly higher compression frankenmotor,  but likely same ac system.  The initial kick in sometimes makes a squeak noise, but engine doesn't even flinch in power.  Doubt it's the flywheel.  If you're in gear already all the weight of the drivetrain plus pulling the vehicle is a bit bigger than just a 10lb lighter flywheel.

It's probably more electrical and sensors than physical.  If you want to make sure, just loosen the ac belt so it lightly grips the pulley.  Next time the ac kicks in if it really is the pump seizing up, the belt would make slipping noises and you'd lose less power.  Doubt it though, compressor pumps either work or make horrible noises before seizing up.

I'm just guessing at this point, I don't know either, but could an overcharged system do this?  Also if the clutch is somehow shorted out, would the coils pull so much amps it makes the electrics go haywire?

Hi, I loosened the belt, and it definitely was chirping/squealing at me, but the A/C was still blowing cold air with less drag. I tightened it just a touch to stop the squealing, and the dragging feeling is back. 

[idosubaru]

Strange. If you take the belt off does the pulley spin freely?

Can you turn the compressor itself over and see if it feels suspicious?  Manually engage the clutch or grab the inner part of the compressor   If you have a other Subaru available compare it to that. They all feel the same in terms of order of magnitude.  If it’s impacting your engine that bad then it doesn’t seem like you’re chasing a minor issue .

There’s internal compressor components, a bearing, and clutch.  And the refrigerant pressures.  

Hate to guess but what else besides the compressor could it even be? 

[1 Lucky Texan]

maybe I haven't kept up very well but, could this be the crank pulley? Symptoms aren't a great match - could make the steering feel heavy while slipping.....?

Edited June 25, 2021 by 1 Lucky Texan

[suprunner]

3 hours ago, idosubaru said:

Strange. If you take the belt off does the pulley spin freely?

Can you turn the compressor itself over and see if it feels suspicious?  Manually engage the clutch or grab the inner part of the compressor   If you have a other Subaru available compare it to that. They all feel the same in terms of order of magnitude.  If it’s impacting your engine that bad then it doesn’t seem like you’re chasing a minor issue .

There’s internal compressor components, a bearing, and clutch.  And the refrigerant pressures.  

Hate to guess but what else besides the compressor could it even be? 

So if it's the compressor, I could grab a used one from car-part, or a local yard? What about replacing oil? I'm guessing the compressors will be empty when I get them from the yard or from car-part. isn't there an intricate measuring protocol necessary? 

Edited June 25, 2021 by suprunner

[suprunner]

Video of the clutch. The part that the belt rotates on spins freely. 

[suprunner]

1 hour ago, 1 Lucky Texan said:

maybe I haven't kept up very well but, could this be the crank pulley? Symptoms aren't a great match - could make the steering feel heavy while slipping.....?

Crank pulley is on tight. This only happens when i've turned the A/C on. 

[idosubaru]

17 hours ago, suprunner said:

So if it's the compressor, I could grab a used one from car-part, or a local yard? What about replacing oil? I'm guessing the compressors will be empty when I get them from the yard or from car-part. isn't there an intricate measuring protocol necessary? 

Yes.  It's easy.  I've done it tons of times.

Oil - doesn't matter. Let me explain...

If you unbolted A/C lines on a brand new Subaru, removed the compressor, then reinstalled it again 4 minutes later - would you be worried about "oil" in the compressor?   

Of course not - it's got whatever oil in it that is distributed throughout the system and will retain that when removed from the vehicle.  Just like a part at a local yard.  A reasonable mechanic or yard knows not to dump the oil out or expose the orifices to debris...they're often stuffed with plastic caps or something to prevent debris/humidity/oil escape when I get one if it's not removed directly from the car. 

I'm somewhat overstating the illustration...but not by much - maybe time and conditions warrant adding some oil, and it is a good idea.   Sure go ahead and do that - no it's not precise.  You'd have to try really hard to get it wrong, you don't sound like that type. 

Imagine adding up all the internal surface area of the compressor guts, air lines, evaporator, drier, etc.....there's gobs of square inches of surface area.  Get it close.  If you think you should add 1 unit of oil....and you add 2....it won't matter - it'll be distributed over such a large surface area that the small amounts we are talking about are inconsequential.    If you didn't add any then all of the cumulative oil in the system will over time just redistribute itself into a slightly thinner layer covering the innards of your compressor (which has it's own residual oil already in it - they didn't dump cleaner down the thing!).  

You can never known how much oil to add so it's always somewhat of guess.  How many times has your A/C been worked on from brand new, how much oil has been lost due to depressing the valve for charging or testing over the years, has any of the oil "degraded", how many parts have been replaced...same goes with the "new" compressor -you can't cut it open and see how much residual oil and film is extant in the compressor.  so it's one big huge guess.  

Also there's no need to pull a vaccuum.  Remove your compressor, bolt the new one in place.  Very little air got into the system and what little humidity was in the "new" compressor will get absorbed by the drier.  There's basically zero chance of all the cataclysmic nonsense people like to rave about online...it's crazy talk and practically speaking never happens to subarus unless you're a hack.  Add 18-22 ounces - whatever yours calls for and you're done.  If you live around exceptional humidity/heat or are transporting frozen goods in the cabin then pull that vacuum and get it perfect. 

Yes - lots of shops//mechanics/DIY/HVAC people would not say anything close to what I just said....but practically and physically thats' what's happening.  Sure - don't be dumb.  Don't buy an unknown cheap compressor from some guy who had to unburry from the back yard garden pile and clean the bugs out of the holes -  and dont' randomly guess on how much oil to add.  Looks it up and make a very rough educated guess - you'll be right.   By your sense of talking about this and detail and interest in diagnosing this - you sound like you know what you're doing and not about to just guess/hack/and roll dice here. 

So yeah - it's easy.  I've done it a ton of times.  I've bolted on ancient Subaru compressors older than yours, some I've added oil, some I haven't....same result every time.  They work and never need replaced again.   But compressors here are cheap and easy to come by and I often have them on hand...so I get you that you might want to diagnose it more first and make sure it's the compressor if they're harder to come by there. 

Edited June 25, 2021 by idosubaru

[heartless]

thanks for the clarification on the oil side of things, @idosubaru - the thought had crossed my mind as well... especially considering that my AC compressor kicking in is pretty much unnoticeable when driving - at idle, yes, you can tell when it kicks in or out, but driving down the road, cant tell at all. Granted, mine could use a little bit of a charge boost - it is struggling a bit on those really hot, sticky days, but does ok for the most part.

[idosubaru]

4 hours ago, heartless said:

thanks for the clarification on the oil side of things, @idosubaru - the thought had crossed my mind as well... especially considering that my AC compressor kicking in is pretty much unnoticeable when driving - at idle, yes, you can tell when it kicks in or out, but driving down the road, cant tell at all. Granted, mine could use a little bit of a charge boost - it is struggling a bit on those really hot, sticky days, but does ok for the most part.

me too! I was concerned before too  

Good grief sorry if you read all that. My goodness that’s long. But that’s sort of a condensed version of what happened for me to get over my own uncertainty and what I was hearing from many others including professionals. 

20 years ago most of what I heard locally or online was dire warnings about high pressures and death and AC systems getting filled with debris from failures caused by AC DIY attempts like I was trying to do.....

I was concerned too the first time or three replacing AC stuff. So I think I know what you mean. eventually I did a bunch of them, let my engineering mind wander into what was actually going on inside: amounts, surface area, recommendations, etc, and it simplified things. 

Edited June 26, 2021 by idosubaru

[nvu]

23 hours ago, suprunner said:

Hi, I loosened the belt, and it definitely was chirping/squealing at me, but the A/C was still blowing cold air with less drag. I tightened it just a touch to stop the squealing, and the dragging feeling is back. 

Likely compressor, but also other things to check. Let's assume the system is somehow overcharging and causing enough back pressure to seize the compressor.  It could also be blockage or a kink in the lines.  Let off some gas a bit at a time and see if things improve.  Since the worst case is replacing the compressor anyways.

And if you do end up taking it apart, consider taking time to remove the expansion valve and look at the oil that comes out of the evap core.  Dark and black is not the best, but normal wear and tear.  Poke something in the lines like a pipe cleaner or qtip, if there's clumpy stuff or sludge, that's what's causing the clogs. Usually replacing the entire evap core is less hassle than flushing.

Get a box of those assorted green hbnr orings beforehand.

 

[suprunner]

15 hours ago, nvu said:

Likely compressor, but also other things to check. Let's assume the system is somehow overcharging and causing enough back pressure to seize the compressor.  It could also be blockage or a kink in the lines.  Let off some gas a bit at a time and see if things improve.  Since the worst case is replacing the compressor anyways.

And if you do end up taking it apart, consider taking time to remove the expansion valve and look at the oil that comes out of the evap core.  Dark and black is not the best, but normal wear and tear.  Poke something in the lines like a pipe cleaner or qtip, if there's clumpy stuff or sludge, that's what's causing the clogs. Usually replacing the entire evap core is less hassle than flushing.

Get a box of those assorted green hbnr orings beforehand.

 

Thank you. How do I capture the system gasses without venting to the atmosphere? How much would a shop charge me to just take a little bit out? 

[suprunner]

23 hours ago, idosubaru said:

Yes.  It's easy.  I've done it tons of times.

Oil - doesn't matter. Let me explain...

If you unbolted A/C lines on a brand new Subaru, removed the compressor, then reinstalled it again 4 minutes later - would you be worried about "oil" in the compressor?   

Of course not - it's got whatever oil in it that is distributed throughout the system and will retain that when removed from the vehicle.  Just like a part at a local yard.  A reasonable mechanic or yard knows not to dump the oil out or expose the orifices to debris...they're often stuffed with plastic caps or something to prevent debris/humidity/oil escape when I get one if it's not removed directly from the car. 

I'm somewhat overstating the illustration...but not by much - maybe time and conditions warrant adding some oil, and it is a good idea.   Sure go ahead and do that - no it's not precise.  You'd have to try really hard to get it wrong, you don't sound like that type. 

Imagine adding up all the internal surface area of the compressor guts, air lines, evaporator, drier, etc.....there's gobs of square inches of surface area.  Get it close.  If you think you should add 1 unit of oil....and you add 2....it won't matter - it'll be distributed over such a large surface area that the small amounts we are talking about are inconsequential.    If you didn't add any then all of the cumulative oil in the system will over time just redistribute itself into a slightly thinner layer covering the innards of your compressor (which has it's own residual oil already in it - they didn't dump cleaner down the thing!).  

You can never known how much oil to add so it's always somewhat of guess.  How many times has your A/C been worked on from brand new, how much oil has been lost due to depressing the valve for charging or testing over the years, has any of the oil "degraded", how many parts have been replaced...same goes with the "new" compressor -you can't cut it open and see how much residual oil and film is extant in the compressor.  so it's one big huge guess.  

Also there's no need to pull a vaccuum.  Remove your compressor, bolt the new one in place.  Very little air got into the system and what little humidity was in the "new" compressor will get absorbed by the drier.  There's basically zero chance of all the cataclysmic nonsense people like to rave about online...it's crazy talk and practically speaking never happens to subarus unless you're a hack.  Add 18-22 ounces - whatever yours calls for and you're done.  If you live around exceptional humidity/heat or are transporting frozen goods in the cabin then pull that vacuum and get it perfect. 

Yes - lots of shops//mechanics/DIY/HVAC people would not say anything close to what I just said....but practically and physically thats' what's happening.  Sure - don't be dumb.  Don't buy an unknown cheap compressor from some guy who had to unburry from the back yard garden pile and clean the bugs out of the holes -  and dont' randomly guess on how much oil to add.  Looks it up and make a very rough educated guess - you'll be right.   By your sense of talking about this and detail and interest in diagnosing this - you sound like you know what you're doing and not about to just guess/hack/and roll dice here. 

So yeah - it's easy.  I've done it a ton of times.  I've bolted on ancient Subaru compressors older than yours, some I've added oil, some I haven't....same result every time.  They work and never need replaced again.   But compressors here are cheap and easy to come by and I often have them on hand...so I get you that you might want to diagnose it more first and make sure it's the compressor if they're harder to come by there. 

Alright, thank you. What do you think about trying to find a used compressor over a remanufactured over brand new? I was looking to call a couple yards up in the northern latitudes, hoping even with higher mileage it might have seen less usage because of the fewer hot days... Whereas buying something used down here in the desert, and I'd guess it's probably close to toast?