Modern Automotive A/C System Advice

[keithb7]

Hi folks this topic is in regards to my daily driver, a 2006 Mazda 3:

 

Last spring my A/C was not working.  I found a rock had punctured a hole in my condenser. I purchased a new condenser. It came with a new receiver dryer as well.

I installed both. New seals were used. I tested the system for leaks. None. Pulled a vacuum on the system for about an hour. I added 2 oz of PAG oil. The system calls for 6 oz of PAG oil, but 4 oz sits in the compressor they say. I added the proper amount of R132a and the system blew cold air. It worked for a little while then no more cold air. I left it alone over the winter. I just did some more trouble shooting today.

 

The system still has a charge. No leak down. I have a gage set.  When the A/C is turned on I am getting no increased pressure reading on the hi-low gauges. I measure 12V at the compressor, at the clutch wire connection.  The compressor is not working.  See some excessive wear on the compressor belt. Signs of a possible compressor seizure.  I suspect I may have not added enough PAG oil when I installed the new condenser,  then the compressor locked up. This is an original 2006 compressor. 18 years old. Vane style that are known to be problematic. Just the compressor clutch coil could be bad, yet for its age I figure it's lived a good life. I'll replace it.

 

I was thinking I'd order a new compressor and belt. Install it with new seals.  Then take the car to a proper A/C mechanic to flush the system out, pull a vacuum, add the correct amount of PAG oil, then add the proper R134a. I'll explain to the tech that I changed the compressor, belt, reciever dryer and condenser. 

 

Does this sound like a reasonable plan? I won't charge or run the system after the new compressor is installed. I'll drive it straight to the garage.

 

Why am installing my own compressor? The cost savings are considerable. $300 for me to buy one and install it. $1000 at the garage, plus install labor. Or maybe I can do all this myself at home. I'm just unsure if I can flush out the A/C system properly and add the correct amount of PAG oil. How do I ensure I get all the old PAG oil out of the system? I've not done A/C work before and have limited knowledge. 

 

Thx. Keith

Edited April 6 by keithb7

[Ulu]

These systems run with very little oil. Over-oiling is actually a worse issue.

 

If any of the the old desiccant had leaked into the system, you will likely have a plugged hose or orifice. If the system sucked dirt in the same could be true.

[Dave72dt]

There should have been an expansion valve or orifice tube changed as well.  One of the common problems now is the tubes in the condensers are quite small and can not be flushed well so if the old compressor trashed itself, you new condenser may also be trashed.  For warranty reasons most suppliers have a list of parts that all have to be replaced to validate it.  A clutch bearing can give the appearance of a locked up compressor also.  You can drain the oil from a compressor for measurement to determine how much is in the unit.  Some new compressors come oil in them and some without so it might not hurt to do a drain and measure on the new one if you go that route.

[JBNeal]

AC techs have told me the same thing over the years:  if the compressor puts metal shavings in the system, then everything needs to be replaced as those shavings are practically impossible to completely remove, perpetuating damage to subsequent replacement parts...that gets expensive.

 

Take that buggy to a good AC tech for diagnostic, then float the idea that you can replace components if they can evacuate the system 1st then charge the system after parts replacement.  The AC techs I have talked to have not been crazy about turning wrenches but like working on multiple vehicles doing diag and evac/charging systems...they make more $$$ and don't get as dirty that way.  And I have saved a bundle by turning my own wrenches and letting the AC techs hook it up to their machines beforehand and afterwards. 

 

On component replacement, follow the oil requirements precisely, which can involve draining the compressor to verify amount...that is tedious, but vital as over oiling can lead to problems as mentioned, such as burning up the compressor.

[Ivan_B]

On 4/7/2024 at 12:32 AM, keithb7 said:

Does this sound like a reasonable plan?

Probably not, sorry

I am +1 for the A/C shop. I've tried fixing my own A/C, years ago, the same thing happened - happy cold cruising and then the compressor seized. Not sure what happened, since I did not touch it afterwards. If the shop does the work themselves, at least they should be able to provide you with some warranty. I doubt they will install your parts or work with the DIY installed parts, though.

[Ulu]

Too much oil can cause it to migrate to the desiccant. It swells the bag, which is mainly to collect water. If the bag swells and bursts, it can clog the expansion valve immediately. Then the hose from the dryer plugs too.

 

But, where the desiccant goes depends on the design. Mopar put the dryer before the expansion valve. GMs put it after the evaporator, and called it the accumulator.

 

I believe that the theory was an accumulator could hold extra contaminants and keep them out of the compressor. My Cadillac and Chevrolet both had this and being General Motors products they probably had extra contamination too.

 

The dryer on the Mopar was on the high-pressure side of the system. It was made of steel, while the accumulator was on the low pressure side of GMs & was made of aluminum, I believe.

Edited April 8 by Ulu

[keithb7]

Following up on what I ended up doing with my A/C system as outlined in post 1.

 

Took my old compressor off and dumped the oil. It was clean and looked good. No failure in compressor. The original compressor on my car was a vane type. Prone to shorter life than a radial piston type. I ordered a brand new radial piston compressor off Rock Auto. It was prefilled with PAG oil. The proper amount they claimed.  I installed the new compressor and re-installed hoses. I got way down under the dash and replaced 2 cabin fresh air intake filters. I booked an appointment at the A/C shop. Told them that I recently installed a new compressor and last year a new condenser and receiver dryer. I asked them to remove the new compressor and drain it. Install the correct about of oil. Replace o-ring seals. Pressure up system and test for leaks. They found none. They Sucked the system down for a while and refilled it with refrdigerant. Installed a new Compressor drive belt.

 

They told me it blows ice cubes out the dash now. I agree. System works very well. I saved a ton by buying my own new condenser, dryer and compressor,then installing them myself. They had no issue with me doing that myself. Good guys to deal with. I'll be recommending them. Happy to say I'll be cool this coming summer!