A/C warning light: Service A/C

[Steve2150]

Have a 1990, had a/c compressor changed about 8 months ago, was working fine after that. Yesterday while still blowing cold air the Service A/c soon light came on. Today the light is on but no cold air, as soon as I press the auto button the econo button light comes on. I noticed that when pressing the outside temp button it was the same temp as what the A/C was set at. Any ideas what it could be???

[drtidmore]

Once the BCM sets a low pressure fault in the AC system, you have to pull the battery to reset the BCM otherwise, the BCM will not engage the compressor clutch period.  Really sounds like a low refrigerant situation, but could be the power steering pressure switch as 89RedDarkGrey mentioned.  You did not mention if the system was returned to R-12 or updated with R-134a when the compressor was replaced.  If updated to R-134a the O-rings in the ends of the various hoses associated with the system must be swapped out as well otherwise there will be slow leaks.  R-134a is a smaller molecule that R-12 so requires a different O-ring.  Also, it never hurts to use R-134a with a leak stop agent just to seal up the system overall.  I did a compressor, accumulator, o-ring swap with system flush and update to R-134a over 3 years ago and have had zero issues since.  

[Fox W.]

I overhauled my A/C system in 2011, DYI job and it has been flawless since.  If you need any help I'll do my best.  

 

If your system is already R134, then just go get yourself some UV dye and a R134 recharge kit.  Total cost will be around $40 to $60.  

Also get a UV light, such as https://www.amazon.com/TaoTronics-TT-FL001-Flashlight-Blacklight-Ultraviolet/dp/B00RV8PREI/ref=zg_bs_6476726011_1?_encoding=UTF8&psc=1&refRID=3EKJTRDF9CJ8DG5RKVD8

 

Follow the instructions on the recharge kit, bring your system up to nominal pressure.  

 

Then add the UV dye (usually just a 3-second injection) while the compressor is engaged..   All of this is done via the low-pressure fitting.    

 

Use/drive it around for awhile.   Then check with the UV 'black-light' flashlight

 

This will tell you where the leak is coming from.   If you don't see anything (except the bits around the port you used to inject it)  then check the evaporator by removing the control module  (check this forum) and look inside the box with the UV light.   

 

If you are using R12, then take it to a pro I guess.   Good luck.

 

Edited March 15, 2017 by Fox W. (see edit history)