Air conditioning, not working, no power to relay

Hi everyone. First I apologize if there is a post for this problem, but I couldn't find it. I have a 2008 Legacy 3.0R, last fall the AC stopped working and I forgot about it until now, it is getting hot. My previous Impreza had needed a recharge which I did easily and figured I would do it again to my Legacy. This time, things are not so simple.

 

First I started the car and turned on the AC. The compressor did not start up and I put the gauge from the refrigerant can on the low pressure line. It read high pressure in the red (not really expecting anything meaningful without the compressor running). Then I found the relay and pulled it. The relay tested fine. I tested the socket and found no signal power. I jumpered the relay contacts, the AC clutch engaged and I got cold air inside. Also, the refrigerant low pressure gauge started to read green at this point.

 

So it seems my system is fine, there something is stopping the car from engaging it. Any ideas? Is there a way to check the pressure sensor/switch?

 

thanks!

 

Tom

I wonder if the system is overcharged, and that's preventing it from turning on. I am an AC newbie though, and I can't remember what the low pressure value will be with the AC off. FSM also says to check "Fuse (M/B No. 8, F/B No. 22, 31)".

more ac system specs

https://legacygt.com/forums/showpost.php?p=5435476&postcount=14

 

Edit: I know "Doesn't respond promptly" doesn't fit your problem description, but.. I think the troubleshooting steps given might still be helpful. Also, this is what the lock sensor is supposed to look like, to find and check it

https://www.subaruoutback.org/threads/05-h6-a-c-compressor-cluth-relay-not-getting-12v.424202/post-4874697

Edited June 6, 2020 by apexi

I understand you pretty well... I have the same problem now and don't know what to do

Hi everyone. First I apologize if there is a post for this problem, but I couldn't find it. I have a 2008 Legacy 3.0R, last fall the AC stopped working and I forgot about it until now, it is getting hot. My previous Impreza had needed a recharge which I did easily and figured I would do it again to my Legacy. This time, things are not so simple.

 

First I started the car and turned on the AC. The compressor did not start up and I put the gauge from the refrigerant can on the low pressure line. It read high pressure in the red (not really expecting anything meaningful without the compressor running). Then I found the relay and pulled it. The relay tested fine. I tested the socket and found no signal power. I jumpered the relay contacts, the AC clutch engaged and I got cold air inside. Also, the refrigerant low pressure gauge started to read green at this point.

 

So it seems my system is fine, there something is stopping the car from engaging it. Any ideas? Is there a way to check the pressure sensor/switch?

 

thanks!

 

Tom

 

From what you are describing, wouldn't that point to either the relay actually not working correctly or the trigger signal is not reaching the relay. I would be tempted to swap the relay with a known good one to test that. If that doesn't work, then start chasing the signal wire. Recommend using the service manual to aid with troubleshooting if you don't have it already.

Have you contacted the repair service? I think they can help you.

This can be a serious problem. You have contacted the repair service. Just this behavior of the air conditioner may not lead to the most pleasant outcome. I bought an air conditioner about a year ago, which began to work poorly after three months of work. But there was nothing serious, that is, the smell of burning or some strange sounds. Four months later, when it was turned on, it began to smell weird and warm air began to come out of it. Then I decided to search the Internet for what to do if aircon not cold. I found video tutorials on how to deal with this problem myself. Still, in my opinion, the best solution was to hand it over for repair. Edited May 18, 2021 by Toji

I also think that with such a problem it is better to address in repair service. Indeed, it can be a severe problem. And if you try something, you will aggravate the situation. It is better to entrust such things to professionals because all the techniques are fragile and require special care. Honestly, I don't try to repair myself, even an ordinary air conditioner at home. The more I would not go into, I wouldn't go into a machine. Moreover, now many services are specializing in repair and aircon chemical wash prices. They tackle problems of any complexity any and do their job quickly and efficiently. Edited August 4, 2021 by ZosCols

i have a question about my ac took it to the shop today had it flushed and they told me the cycling switch wasn’t putting power to the compressor he jumped the compressor just to show me it worked and it came right on blowing good cool air he gave me a part number of 1618 off some site. but can anyone tell me the actual name of that switch its the one on the drivers side behind the wheel well

i have a question about my ac took it to the shop today had it flushed and they told me the cycling switch wasn’t putting power to the compressor he jumped the compressor just to show me it worked and it came right on blowing good cool air he gave me a part number of 1618 off some site. but can anyone tell me the actual name of that switch its the one on the drivers side behind the wheel well

 

I believe that is the high pressure switch.

 

I have also run into this problem this past month and diagnosed all easily accessible switches and fuses and everything checkout ok. I still bought an relay just in case as it seems that after i tested the relays, the system started working properly. either way i am glad it is working properly for now. it is hot here in Houston.

The factory service manual just calls it a pressure switch, or triple pressure switch. I tried to find it at parts.subaru.com, but I think subaru makes you buy the whole pipe to get that sensor.

 

I believe your mechanic knows of a place where he can just get the switch, without having to buy the whole pipe like subaru makes you do. I wish I knew what brand or something, I tried googling various words with 1618 and didn't get anything.

 

Edit: Maybe it's this switch, Santech MT1618

https://www.autozone.com/cooling-heating-and-climate-control/a-c-switch/p/santech-a-c-switch-mt1618/121102_481672_8905

http://www.santech.com/downloads/flyers/LIT-0242_Santech_2012_New_MT_Products.pdf

Other options when you cross reference the oem honda part number in the third image

https://www.rockauto.com/en/partsearch/?partnum=80450-SFE-003

Edited August 3, 2021 by apexi

I would check the control head first. A scanner should be able to tell you if the computer is recognizing the a/c switch as being on, which energizes the relay.