AC relay and Test Mode question

[ji126652]

My AC isn't working on my 2012 Subaru Legacy 2.5i, so I want to run test (delivery) mode to see that the electronics in the compressor is working. I know how to do this, but when turning test mode off, is it as simple as turn the key off and then disconnect the green cables? Is there any reprogramming needed?

 

Also, I'm confused as to where the AC relay is, or if there even is one. In the fuse box, it says there should be an AC relay, but looking, there's nothing there, nor is there even metal connectors for a relay... (I tried uploading pictures but it won't let me).

 

Looking at the repair manual, it looks like there is only an AC compressor fuse? Is this correct?

[Scubaboo]

Sorry I have no idea, but any particular reason you are going into that? I think a refrigerant pressure gauge will give you a lot of info on where the problem is.

 

What electronics does the compressor have besides the clutch? Is it a variable displacement unit?

[ji126652]

Sorry I have no idea, but any particular reason you are going into that? I think a refrigerant pressure gauge will give you a lot of info on where the problem is.

 

What electronics does the compressor have besides the clutch? Is it a variable displacement unit?

 

I think just the clutch, so yea that's all I'd want to check by doing this.

 

Dumb question here, but if I do a manifold gauge pressure check (following the service manuals instructions), then I don't need the system purged right? In other words, no air/contaminants are introduced?

[FLlegacy]

I believe it is variable displacement, so it isn't just a clutch, well I guess technically it is a wobble plate clutch I believe. The factory service manual has a whole troubleshooting section for the hvac unit. You can find all your questions answered there.

[Scubaboo]

I think just the clutch, so yea that's all I'd want to check by doing this.

 

Dumb question here, but if I do a manifold gauge pressure check (following the service manuals instructions), then I don't need the system purged right? In other words, no air/contaminants are introduced?

 

I have not had to check clutch operation yet on the Legacy but on most cars it's just give it 12v and it should engage or not.

 

Yes attaching an AC manifold gauge does not require a purge and they are designed to quick connect to a car's refrigerant ports to minimize refrigerant loss. No appreciable air/contaminants are introduced.

 

The mechanical variable displacement valve is easy too, if there is refrigerant and the clutch is engaged but cooling randomly disappears or is gone, its usually the valve. Gauge will show it too.

[ji126652]

I believe it is variable displacement, so it isn't just a clutch, well I guess technically it is a wobble plate clutch I believe. The factory service manual has a whole troubleshooting section for the hvac unit. You can find all your questions answered there.

 

 

I looked and it says there's a self diagnostic HVAC mode, but I don't even have all the buttons to do it, so I guess it's not for my 2012 Legacy model?

 

Every other diagnostic seems to require the Subaru Select Monitor... Would something like BTSSM be able to replace that for getting all the diagnostic codes (DTC)?

 

Actually it does explicitly say to check the refrigerant pressure if cold air stops blowing (which is what happens in my car), and the instructions for that seem easy enough. I've also read that the O-rings suck and they commonly go bad, causing a leak.

 

Anyone know of a decent, relatively inexpensive set of manifold gauges to check this? I'm NOT looking to possibly fix this as a DIY job (i'll go to a mechanic for that), but it'd give me a piece of mind to know whether the pressure is so low that the compressor isn't kicking in...

Edited May 4, 2022 by ji126652

[Scubaboo]

If your HVAC controls have a diagnostic mode, that will help immensely.

 

Most HVAC self diagnostics I've dealt with in other cars will have refrigerant pressure sensor access which will tell you if you have refrigeramt in the system.

 

Usually it will give you actual values for other AC system sensors too, which can help you deduce faulty sensors. Those can cause a compressor to stop working too. Sometimes they have fault codes too, like for a faulty clutch as you are exploring.

 

If you cant access diagnostics and dont have a gauge yet, a quick and dirty test is to simply open the charging port by the compressor and poke the shrader valve. If it's empty, add refrigerant first then check for AC function and leaks. It's mentioned to check for refrigerant in the manual as this is the usual cause for no AC.

[FLlegacy]

An AC diagostic at many places is pretty cheap usually. It literally is the tech hooking up gauges and looking at the pressures.

 

You have manual controls so I don't think the diagnostic mode is going to do anything. Even on the auto hvac the diagnostic mode is to make sure the controlls are working correctly it isn't for the mechanical side of things.

 

I think you are in the wrong section there, there should be a troubleshooting section for the HVAC system not just the control panel.