Friday, December 28, 2018

SC430 - A/C issues and fix.

It was October and with the weather in the low 60's you wouldn't think I would have a problem with the A/C not working but well you kinda need the A/C to defog your windshield and windows. Also I just wanted it fixed. Matt and Taylor at Insomnia Motorsports was kind enough to check on the system. The compressor was not kicking on which could mean low refrigerant, when it was bypassed the compressor was kicking on. We filled up the system with r134a to spec and the compressor was kicking on, as it was supposed to but was not cooling. The pressures in the lines were too high on both the high and low pressure lines which sort of points to a bad expansion valve. Also with the expansion valve being the cheapest part in the system I opted to change that out first. Ordered a new denso expansion valve and swapped it in. Matt connected the A/C recovery, recycle, and recharge machine and pulled a vacuum for about 30 minutes, and verified that there were no leaks etc and filled it back up with r134a refrigerant. A/C was blowing nice cold air again and was on my way.

The expansion valve sits right about the accelerator pedal. Below is a picture of it with some foam insulation removed. The gap between the aluminum blocks is where the expansion valve sits. Below is the picture of the low pressure line that comes out of the compressor that has the muffler on it that I was going to replace. 

It was a week or two later that I drove the car again and well to my annoyance the A/C was not working again. When I checked the pressure in the lines there was pressure so since I had just replaced the expansion valve the probability of that going bad again that quick I thought was slim. The only other thing I could think about was that the compressor was going out. When the compressor goes out or starts to go out it can pump metal shavings through the system and could get caught up in various parts of the system especially the expansion valve which can prevent the expansion valve from working properly. 

So my train of thought was to automatically change every single component in the A/C system. The system consists of Compressor, Condenser, Dryer, Evaporator, Expansion Valve, O'rings and Mufflers and Lines. The only problem was I was not comfortable in taking the whole dash board out to change the evaporator. The Expansion valve even though it sits behind the dash board I could access it without taking the dash board off. So since I didn't see a drop in pressure I ruled out the possibility of a leak which meant the evaporator did not have a leak as well. On the low pressure line there is a muffler on the line connected to the compressor. I believe this muffler is there to catch any metal shavings that might come from the compressor in case it blows up. Also the dryer would catch these shavings as well. Since the evaporator did not have a leak I chose not to change it. Everything else I could access easily and change. 

The only components I wouldn't be changing would be the evaporator and the lines. To clean the evaporator and the lines of any possible shavings I was going to flush the system. Flushing air-conditioning systems is extremely important when repairs are carried out or if a compressor is damaged. The flushing process removes impurities and harmful substances from the air-conditioning circuit. You should not or cannot flush compressors, expansion valves, or filter dryers and mufflers. Use adapters to bridge these components during the flushing process. Once the flushing process is complete, the valves and filters must be replaced. In this method, the air-conditioning system is cleaned with a special flushing liquid (in combination with compressed air).

Below is a picture of the block on the firewall where the lines go into.

I wanted to flush each component separately as much as I could. Flush lines individually and the evaporator individually. The expansion valve is located write behind the firewall under the dash board so without creating a mess inside the car I thought I could remove the lines going into the firewall, leave the expansion valve in place and flush the evaporator out. This would have been great if the expansion valve was on the engine side of the fire wall. Looking at the expansion valve you can see why you cannot really flush through the expansion valve. To provide an easy flow of flush through the system I decided I could take the expansion valve apart. There is a hex screw at the bottom you can remove and you can remove a spring and valve that sits in it. Once that is out I drilled the stem out and made the passages bigger so that it matched size of the lines going in and out of the expansion valve. Put the hex screw back in place and install it back in the car after a thorough cleaning with brake cleaner and forced air. No point adding metal shavings into the system.

Once the modified expansion valve was in place I removed all the components, compressor, condenser, dryer and muffler and flushed the evaporator out. Filled up the flush machine with the cleaner and sprayed it in pulses till the cleaner started coming out from the other port on the firewall. I let the cleaner sit there for about 20 minutes and then used compressed air till all the cleaning liquid flushed out. Then I kept going for another 15 minutes of just compressed air flowing through the evaporator. I capped both the ports shut and continued to flush the lines while I let the cleaner dwell etc. I did that process 4 times and the last time around instead of 15 minutes I did 30 minutes of compressed air just flowing through the system. Make sure you air the system out with the compressed air to ensure all the flush is out of the system. The ideal way is to use nitrogen but I didn't have that. After each line etc is cleaned I capped them off.

The cleaning process I think is what takes the longest amount of time. The removal of all the components are pretty straight forward, well documented and not really time consuming. With all the old parts out I proceeded to reinstall all the new components making sure the lines were capped out so no foreign debris is introduced into the system.

All the new components:

Out with the old:

When replacing the compressor I drained all the PAG 46 oil out of the old compressor and since all the components was new and the lines were flushed out there is no oil in the system. The system calls for 4oz of PAG 46 oil. My thought process was to distribute the oil through the system, put about 3oz of PAG 46 oil in the compressor and 0.5 oz in the evaporator through the lines and 0.5 oz in the condenser. When filling the compressor with oil turn the clutch so that the oil can get distributed into the compressor. I didn't think the compressor could hold 4oz of oil but it took it. I used a syringe to measure the oil so I could be as accurate as I could. 

With everything oiled and cleaned I installed all the new components. Connected all the lines etc with new nitrile  o'rings.

With all the new components replaced and connected I wanted to make sure there are no leaks etc. You can do a vacuum test and make sure there are no leaks under vacuum, however, the AC system runs in excess of 180psi and sometimes under vacuum it might not show leaks but under pressure it can have leaks. The best way to check for leaks under pressure is to actually pressurize the system. To pressurize the system I used Nitrogen. A buddy of mine does HVAC systems for homes etc and that's what he uses to pressurize systems and check for leaks. Thanks Sam. He pressurized the system for me with Nitrogen and verified that the pressure holds even after an hour. 

After verifying that the system has no leaks under pressure I vacuumed the system as well to make sure that there are no leaks under vacuum and vacuum helps get rid of any moisture or other solvents that might still be present in the system. Might be excessive but better safe than sorry.

I let the vacuum run for over an hour and even after three hours the vacuum held with no change in the pressures. 

At this point it is ready to fill with refrigerant. The SC430 AC system calls for between 21 to 23 ounces of  R134a refrigerant. I got the system hooked up to a HVAC refill and recovery machine and had the system refilled. The AC in the car is back to being ice cold, not that I'll be using it anytime soon, but the satisfaction of knowing it is working and hopefully done right keeps my mind at ease. 

-AJ Abraham

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