PSA: Don't Even start these cars without refrigerant

[Ifixtheinternet]

2013 Legacy 3.6R.

This post is somewhat of a PSA and question.

So the past couple of Summers I've had an obvious AC refrigerant leak - It will stop blowing cold by the next summer and I have to have it refilled. last summer it didn't even last through the season.

Took it to a local shop and they detected refrigerant coming out of the vents, so the evaporator needs to be replaced (or possibly an o-ring).

The lead tech mentioned this type of compressor shouldn't be run with low refrigerant, otherwise it can get damaged, and that while the vehicle should stop it from running in this scenario, it appears mine wasn't. so when it started getting low again, I unplugged the electrical connectors to the compressor.

I've done a lot of car maintenance and repairs myself, have a lot of tools, figured I could tackle this job. so I took it to the shop and had them evacuate the system completely before attempting to replace the evaporator. It appears this was a big mistake.

I picked up the car from the shop. Did not engage the A/C. As soon as I started driving away, I heard a strange Whirring / mechanical noise from the engine compartment that lasted a few seconds and then went away. I was concerned about this but not sure what it was at first.

Couple days later, After following an instructional video for 2014 Outback, which shows that you can access the evaporator from the lower dash without removing the whole assembly, I found that was not correct. I acquired a full service manual, and it turns out the whole dash has to come out, coolant drained, an entire HVAC box removed from the vehicle to get this done. Boo.

Then I saw it, a big warning right at the beginning of the instructions:

"Do not start engine before refilling the system."
"If engine is started before system is filled, replace compressor".

Fuuuu . . .

So the noise I heard was likely the compressor being destroyed.

I haven't talked to the shop yet about it but I'm guessing they're unaware of this caveat, and they just did what I asked.

I was surprised to learn of this, that if the leak is so bad that everything leaks out, the compressor will get destroyed? Surprised I hadn't heard about this before.

Sooo, I'm trying to figure out how screwed I am.
I know when some compressors go bad, they can send debris through the entire AC system, which then all has to be either replaced or flushed. Anyone know if this is the case with these compressors? or is there any way to check that?

So PSA: Don't even drive these cars if there's no refrigerant in the system!

[Scubaboo]

That's weird, most all automotive AC systems use a low pressure sensor to prevent the compressor clutch from engaging when there is no/too little refrigerant.

I havent heard of this quirk with any of the AC techs I know.

If the compressor did eat itself hopefully since there was no refrigerant debris did not circulate into the system.

But I wouldnt conclude its the compressor just yet IMO

[Ifixtheinternet]

Well I spoke to the shop about this, and they are confident that it is not damaged. The lead tech's opinion is that the warning in the service manual is overly cautious, like "don't run the engine if oil is 1/2qt low."

To be clear, these compressors are variable output type and do not have "clutches" like the older style compressors. They are always spinning with the belt regardless. Hence the concern. So it would seem that at minimum, the compressor is defeated some other way in a low charge state, instead of with a clutch. 

Apparently most newer cars have this type of compressor.

It doesn't make sense to me that most manufacturers would remove the Fail-Safe of defeating the compressor in a low charge state.

However, seeing that warning combined with a mysterious strange noise right after I drove the car from the shop had me convinced that the compressor was damaged.

Currently the plan is to take the car back on Wednesday, have them fill the system and see what happens. I've decided to put off the evaporator job. since I've discovered how difficult and time consuming it's going to be, I'm planning on getting a heater core and replace that while I'm in there, along with possibly a blend door motor and anything else that might be a good idea while I have everything apart. So on Wednesday, either I or the shop is going to learn something.

[Scubaboo]

The variable displacement types I have experience with actually still had clutches.

I dont know if the GT has the same compressor as the 3.6 but my GT has a clutch.

Either way it has to have a failsafe on it or any refrigerant loss would then automatically trash the compressor.

I would guess that low/no refrigerant would cause the system to move the variable swash plate flat which would give zero compression.

 

 

[cww516]

I would ask them to at least flush the compressor out with compressor oil before they recharge the system, and make sure there's no glitter in there.  Zero displacement on a piston pump means that (nominally) the pistons don't move, but it doesn't mean the pump stops rotating- if the internal bearings are counting on the oil that's normally in with the refrigerant for lubrication, they might be pretty unhappy right now.  It's also worth noting that having the HVAC set to "auto" can still run the A/C unless you specifically hit the button and turn it off.  There's a chance everything is fine, but I'd probably take the more cautious route just in case it's not, so you don't end up having to replace everything else downstream if it turns out the compressor did fail.

[Plastixx]

On 3/26/2024 at 9:30 AM, Scubaboo said:

The variable displacement types I have experience with actually still had clutches.

I dont know if the GT has the same compressor as the 3.6 but my GT has a clutch.

Either way it has to have a failsafe on it or any refrigerant loss would then automatically trash the compressor.

I would guess that low/no refrigerant would cause the system to move the variable swash plate flat which would give zero compression.

 

 

There is no clutch or fail safe. This excerpt from the FSM isn't there just for shits and giggles...

Quote

• After installing the compressor, do not start the engine until the A/C system is charged with refrigerant.

• If the engine is started with no refrigerant charge, replace the compressor.

The dealer I bought my car from pulled the engine to put in a new clutch but never refilled the AC. Since I bought the car at the tail end of winter, I didn't even notice that it wasn't working for a couple of months. I discovered the system was completely empty and knew the compressor was probably toast, but tried to refill the system anyway.

I purchased a new evap valve and desiccant bag kit, since they should always be replaced if the system is opened and they don't cost that much. When I removed the old desiccant bag, it was completely grey and there were metal flakes in the plastic filter. The internals of the evap valve was also covered in grey metallic oily goo.

After replacing the parts and refilling the system the AC worked, but not very well. It's been about 28k miles since then and it's still technically working, but if I watch the OBD live data for the system, it can barely build 100psi on a warm day.

Edited March 27 by Plastixx

[Ifixtheinternet]

1 hour ago, Plastixx said:

There is no clutch or fail safe. This excerpt from the FSM isn't there just for shits and giggles...

The dealer I bought my car from pulled the engine to put in a new clutch but never refilled the AC. Since I bought the car at the tail end of winter, I didn't even notice that it wasn't working for a couple of months. I discovered the system was completely empty and knew the compressor was probably toast, but tried to refill the system anyway.

I purchased a new evap valve and desiccant bag kit, since they should always be replaced if the system is opened and they don't cost that much. When I removed the old desiccant bag, it was completely grey and there were metal flakes in the plastic filter. The internals of the evap valve was also covered in grey metallic oily goo.

After replacing the parts and refilling the system the AC worked, but not very well. It's been about 28k miles since then and it's still technically working, but if I watch the OBD live data for the system, it can barely build 100psi on a warm day.

That is really concerning, sorry to hear.

The car is at the shop now, and I told them to verify if there is any debris in the system before attempting to fill it. They expressed that they had already planned to do that.

It will be really unfortunate if there's damage.

Not only the financial implications, but this shop has been otherwise really good to me and seem very experienced. I would be baffled about how they would not know about this being a thing for at least the past 10 years.

[Ifixtheinternet]

Got a call back from the shop.

They tried to fill the system but The compressor is having "issues". It's building pressure, then losing it, then building it, rinse repeat.

He stated that he wants to refill it with oil in the morning, that maybe too much oil was lost with the evaporator leak. I'm not optimistic.

they also stated that since there was only quarter pound of refrigerant in the system, I was already practically empty. 

Sounds like they're building their case of washing their hands of the problem.

He said he didn't see any debris in the system but It will show up in the morning in the oil if there is some. 

looks like I'm in for some expensive repairs.

 

[Scubaboo]

Well that well and truly sucks, a failed o-ring or hose crimp turns into an entire system replacement with that design.

I just looked and my 2010 GT's compressor is clutched.  Probably different from the 3.6's.

[Plastixx]

2 hours ago, Scubaboo said:

I just looked and my 2010 GT's compressor is clutched.  Probably different from the 3.6's.

I don't think it is. Do you see a control wire for the coil? The pulley on a clutch-less, variable displacement compressor can look more like a clutch than a regular pulley because it's designed to sheer the outer part from the inner in case of a compressor failure that causes lockup.

Early variable displacement compressors were all clutch-less. Eventually they realized how retarted that is, for obvious reasons, and started putting clutches on them.

Edited March 28 by Plastixx

[Scubaboo]

Yup, there is a control wire for the magnetic coil.

i have a 2004 BMW X5, the year BMW switched the AC compressor from a standard Denso to a variable displacement Calsonic.  Those variable displacement Calsonics had pulley clutches as early as back then.  

I didnt know it back then, and it got me scratching my head losing AC intermitently but seeing the compressor clutch engaged, till I learned it was a variable displacement compressor lol! 

[Plastixx]

That doesn't look like a variable displacement comp. I don't see a control solonoid on the bottom rear corner.

[Scubaboo]

Havent really looked into it if the one on my GT is variable.  

Valve placement on the variables are, well, variable...on my X5's Calsonic CSV717 the valve was on the backplate.

[Plastixx]

I would guess that they chose not to use the ECVDC on the GT because of the performance aspect of the car. 

Another easy way to tell is if you have a bi-directional scantool. A system with a standard compressor is "dumb", so there's no control module with live data available for it.

 

[Scubaboo]

I just googled the 3.6 compressor and see what you mean now...totally different hub and big honking valve on the side.

[Plastixx]

Interesting. Just looked at the compressors being used on late model Subarus and they're still clutch-less. Most other makes use clutched ECVDCs. It has to be a desperate cost cutting measure by Subaru. Can't think of any other reason for it.

[silverton]

There's even a scantool break-in procedure. The manual is the same for the H4 and H6.  These variable compressors are for fuel savings, not cost, for their overall EPA rating. Much like FB's can and should be using 5w30 but to meet their rated MPG you must use water.

 

Edited March 28 by silverton

[Plastixx]

49 minutes ago, silverton said:

These variable compressors are for fuel savings, not cost, for their overall EPA rating.

I know the point of a variable displacement compressor is efficiency. I was refering to the fact that Subaru still uses the clutch-less variety.

[silverton]

They're also still using the same general suspension setup from 1993.  Subaru is incredibly slow at adopting new things.

[Ifixtheinternet]

Well it's official, the compressor is toast.

It will temporarily get all the way up to correct pressure but then drop again. It's not making any strange noises while running, so they're convinced it's not damaged to the extent that It has sent debris through the system. I'm still not sure.

Shop said they would cut me a break on the labor of installing a new compressor if I got one and recharging the system, but that's about it.

[Scubaboo]

That sucks, sorry to hear.  I do appreciate you and the others posting their experience, I had no idea Subaru had this poor design on some of their AC systems.

I wonder if it is the variable displacement valve that is toast and the compressor repairable?

Since it can build up pressure but cant hold it, it could be the variable portion malfunctioning, which I've seen repaired in other model compressors by replacing the variable displacement valve.

I doubt it is available as a separate part from the dealer though, but for some compressors you can find them online.

However with the clutchless design another failure could take out more of the system so you may be better off getting new.

 

[Ifixtheinternet]

Yeah I'm going to get a new compressor.

Rockauto has the OE Denso new for 400, or the shop can source One for a little over $500 and warranty it, which I might do.

After talking more with the shop, they're going to work with me. They're going to pressure test my new evaporator and heater core I plan to swap while I'm in there, to make sure they're good before I tear apart the dash. I'm going to get a new accumulator / dryer and expansion valve just to have confidence nothing was damaged from debris.

The shop is going to flush out the lines and the condenser for free at my request, just to be sure we're starting fresh, install the new compressor for me, with the break in procedure which they verified, and refill the system.

It's safe to say that they were dumbfounded that this system can be damaged just by being driven without a refrigerant charge.

I would blame them 100% if I asked them to do a procedure and they didn't look it up or follow it correctly. But I took the car to them and asked them to do something that common knowledge dictates should be safe to do on any vehicle.

This is just a really poor design decision by Subaru that few people seem to be aware of.

Now I have a service manual and will look up any procedure that I'm about to do or bring to a shop to have done. That's my lesson.

[Plastixx]

3 hours ago, Scubaboo said:

Since it can build up pressure but cant hold it, it could be the variable portion malfunctioning, which I've seen repaired in other model compressors by replacing the variable displacement valve.

I doubt it is available as a separate part from the dealer though, but for some compressors you can find them online.

I don't think it's the problem here, but the solonoid/control valve can be found aftermarket (not a dealer part). It can be difficult tracking down the exact one you need though. Sometimes they just get stuck and a whack on the case with a screwdriver handle can free them up.

I wonder how much experience OP's mechanic has with these systems. They don't act like a traditional system. They will cycle the pressure hi/low if there isn't a heat load even if you have the criteria set per the FSM. Temps are still fairly cool in most parts of the country.