A/C Issues...Possible Culprits?

About a month ago I was heading to my friend's house with the family on a 55. Came up on a slower driver, dropped to fourth and got up to roughly 70 while passing them. During acceleration, my A/C decided to start blowing hot air. For the rest of the trip it stayed that way.

 

Fast forward to now: I'm trying to get it fixed. Once in a blue moon it will blow relatively cool for about 5 to 10 minutes before starting to blow hot again. I took it to a local cheap shop today to have them attempt a diagnosis (closest Subaru dealership is an hour away). First thing they noticed was that my system was way overcharged. After further diagnosis they have determined it is one of two issues.

 

 

1. The expansion valve needs to be replaced. "No freon flow to high side from low side".
   
2. The ambient temp sensor needs to be replaced as "outside temp stayed at 82 the entire time, even after a test drive."
   

From doing a bit of reading on the forum, it would appear that the outside temp sensor is not linked to the HVAC system and for some reason only gets its readings while driving a decent distance. I can confirm that it managed to hit about 91 degrees on the way home from the shop, albeit creeping up a degree every so often. It did fluctuate between 90 and 91. According to Google and my weather app it was around 93 at the time, so that's damn close in my mind.

 

 

What would your opinion be on it? I'd rather have some input from other owners before dropping $530 (total, roughly 338 if just doing ambient sensor & recharge or 440 if just doing valve and recharge) on something that may fix the issue.

 

Edit: From what I can find, part numbers seem to be 73730AG00A and 73531AG010 for the sensor and valve, respectively. Does that look right? I ask because the price they quoted me was $60 for the sensor and $75 for the valve. I find it odd that the sensor would be $50 cheaper online but the valve would be $40 higher. Granted I am looking at OEM as opposed to wherever they source their parts.

Edited July 28, 2016 by Tillmorn
Included Part #'s

Did the A/C work fine before? Have you had it worked on anytime recently? It seems suspect to me that the shop immediately jumped to an overcharged diagnosis since somebody would've had to add refrigerant at some point for it to be overcharged. Is the compressor clutch engaged when it is blowing warm air? I'm an amateur A/C guy with all the proper professional equipment.

 

I had a similar issue that ended up being a failing A/C clutch relay in the fusebox. If I tapped the relay the clutch would kick on, but in normal use it only worked maybe 10% of the time. Replaced the relay, and all is well.

 

Outside temperature gauge behavior seems totally normal to me.

Edited July 28, 2016 by Alphius

This is the outside air temperature sensor. MSRP is $9.77, super easy to replace.

 

http://legacygt.com/forums/showthread.php/maine-4th-gen-legacy-outside-air-temperature-sensor-connector-wires-253186.html?t=253186

Interesting. I am having almost exactly the same problem. Most of the time it works fine, but sometimes for not apparent reason, just starts blowing hot air. It feels like the compressor is kicking in, but I need to investigate that further.

 

Thanks for the A/C clutch relay tip. Will have to double check that, as well as the actual clutch on the compressor.

 

My outside air temperature display is working fine.

 

I did have the system leak checked and recharged which improved it's performance when working, but didn't solve the problem.

 

It's been intermittent for awhile, but it's starting to happen more and more often.

Completely random. Sometimes at startup, sometimes after driving for awhile.

Sometimes only for a few seconds, sometimes for a couple of days. Weird.

The outside temp sensor has nothing to do with the AC, the cabin temp sensor controls the AC unit and it's located behind the center dash (behind and under the radio/AC unit).

 

Did you verify the Compressor is engaging when you turn the AC on?

 

Does the air condenser fan come on when the AC is on?

Interesting. I am having almost exactly the same problem. Most of the time it works fine, but sometimes for not apparent reason, just starts blowing hot air. It feels like the compressor is kicking in, but I need to investigate that further.

 

Thanks for the A/C clutch relay tip. Will have to double check that, as well as the actual clutch on the compressor.

 

My outside air temperature display is working fine.

 

I did have the system leak checked and recharged which improved it's performance when working, but didn't solve the problem.

 

It's been intermittent for awhile, but it's starting to happen more and more often.

Completely random. Sometimes at startup, sometimes after driving for awhile.

Sometimes only for a few seconds, sometimes for a couple of days. Weird.

 

These symptoms are the exact symptoms I had when my relay was failing. I bet that's your problem!

I had to replace my A/C relay once as well. Wouldn't come on or would come on for a short time then when it went to cycle it wouldn't come back on.

 

Replaced the relay and all has been OK since. (If you can call Subaru A/C "OK"... It's grossly undersized for a car with the amount of glass the 3rd gen Outback has.)

A lot of you have described what happened over the long run with me before it finally going out (more or less). Most of the time, the A/C would work fine. Once every few months it'd blow hot instead of cold for a little bit before kicking back over to cold.

 

With your suggestions in mind, I'm actually going to take it to the closest Subaru dealership and have them take a look at it. Especially if it ends up being the relay since that sounds like it'll be a significantly cheaper fix than I was quoted by the local shop.

 

Edit: After I find and replace the relay. Because that is something I can comfortably do (my biggest wrenching experiences are things like changing oil, air filters, bulbs, etc.)

Edited August 1, 2016 by Tillmorn

Well...I'm pretty sure it's the relay.

 

Swapped it out tonight with Autozone Part # 221841 19997 Duralast Accessory relay

 

$8

 

They didn't have a cross reference, but this looks close enough. It's a 20A relay which should be sufficient.

 

Now only time will tell.

 

Thanks again !

A lot of you have described what happened over the long run with me before it finally going out (more or less). Most of the time, the A/C would work fine. Once every few months it'd blow hot instead of cold for a little bit before kicking back over to cold.

 

With your suggestions in mind, I'm actually going to take it to the closest Subaru dealership and have them take a look at it. Especially if it ends up being the relay since that sounds like it'll be a significantly cheaper fix than I was quoted by the local shop.

 

Edit: After I find and replace the relay. Because that is something I can comfortably do (my biggest wrenching experiences are things like changing oil, air filters, bulbs, etc.)

 

The relay is easy to find. It's in the fusebox under the hood; if you look at the underside of the lid after you take it off, there is a diagram of all the relay and fuse locations.

Replace ac relay($10ish) and cross fingers.

 

My case the original part worked intermittently.

The relay is easy to find. It's in the fusebox under the hood; if you look at the underside of the lid after you take it off, there is a diagram of all the relay and fuse locations.

 

I managed to get it done without any issues. I've got a little knowledge dealing with things in the fusebox so that wasn't a big concern.

 

Replaced both the A/C Control Relay and the Secondary? Fan Relay since they were both right there today. Yesterday I switched them around to see if it made any difference.

 

Good news is, that was definitely part of the problem. For the first time in over a month I can hear my A/C turning on (metal hissing sound is the best way I can describe it). Unfortunately, it is not getting cold. It's damn well trying to, but not quite there. I think I'm going to take it to the dealership on Thursday. I have a feeling that the shop that claimed the unit was overcharged last week may have screwed up the levels.

Well...I'm pretty sure it's the relay.

 

Swapped it out tonight with Autozone Part # 221841 19997 Duralast Accessory relay

 

$8

 

They didn't have a cross reference, but this looks close enough. It's a 20A relay which should be sufficient.

 

Now only time will tell.

 

Thanks again !

 

Please carefully examine the relay schematic (should be on the top or side) to ensure that it has a protection diode in it. It's not mentioned on the Autozone site for that part number.

 

Subaru had to replace quite a few fried ECMs under warranty because one of the cooling fan relays from the factory didn't have a protection diode built in.

Please carefully examine the relay schematic (should be on the top or side) to ensure that it has a protection diode in it. It's not mentioned on the Autozone site for that part number.

 

Subaru had to replace quite a few fried ECMs under warranty because one of the cooling fan relays from the factory didn't have a protection diode built in.

 

 

Looked at the relay schematic. You are correct. No diode.

 

Thank you !!

 

Stopped at dealer and picked up an OEM unit. 82501AG05B

 

Only $7. Go figure.

https://parts.subaruonlineparts.com/oem-parts/subaru-relay-82501ag05b/?c=Zz1lbGVjdHJpY2FsJnM9Zm9nLWxhbXBzJmk9NzUyNzE5MDUmcj1sYXllcl83JmE9c3ViYXJ1Jm89bGVnYWN5Jnk9MjAwNSZ0PWd0JmU9Mi01bC1oNC1nYXM%3D

 

That should be the part. I'll pick one up from my local dealer.

 

Got the link to this thread from here, https://legacygt.com/forums/showthread.php/ac-issues-270482.html

 

 

I noticed one of the other relay's in the fuse box has the same numbers on it. why not just swap them ?

 

Just installed both relay's, same part for both cars. 05 and 09. Have to wait till the next heat wave now. Oh with tax I paid $11.54

Edited July 7, 2018 by Max Capacity

Max I knew it, your following this thread as well, the relay that was put is the same as the fog lights using, I’m sure that relay is working well because I don’t use the fog lights often maybe once a year LOL, I’ll do the swap and see if it works, then get a new one after or leave it as is. Edited July 7, 2018 by edgemoulic

I use my fog's all the time. I like the look.

 

I guess they say later this week the next heat wave is due...

Well today after work the AC worked great all the way home on the highway. Nice flow and cold air. May be that relay is the fix.

Update, The AC was fine all last summer since I replaced the relay in July 2018.