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Since it is a little slow right now but summer will be here soon. I wanted to start a discussion on the replacement of auto a/c compressor. I would like to hear all opinions on how you go about doing a repair. This could be from the professorial shop to the person trying to save a few dollars.
There will be no wrong answer in this discussion. So feel free to explain your procedure and why you choose that option.
Before replacement, the cause must be determined IMO. Yes, sometimes the compressor is just worn out but many times there is a cause. Loose mounting bolts, restricted airflow across the condenser, Low charge causing loss of lubrication,liquid slugging, and overcharging are all causes of compressor failure. When a compressor fails,careful observation of the condenser is required. Some condensers can not be flushed and must be replaced.
I completely agree that the cause of failure should be determined, or at least the results of failure. The post-mortem inspection determines the appropriate corrective action. Just installing a new compressor without removing debris or verifying the quantity and quality of lubricating oil, is probably the biggest and primary cause of rapid and repeat compressor failure. I think everyone from the pro to the backyard is trying to save a few dollars. However, doing it right, and doing it once; proves to be the most cost effective approach.
When I install a new compressor, I remove the compressor, the filter/dryer (or accumulator), and the TXV (or OT). I then flush the Evap in the direction of flow and blow until completely dry (no matter how long it takes). I then flush the condenser in the opposite direction of flow (to back out debris) and dry, dry, dry. I will use and clean the hoses as I flush these two heat exchangers. I will drain the (shipping) oil that comes in the new compressor even though the paperwork says it is good and the right quantity (I just don't trust it). I will then install the compressor, new filter, and new orifice, add the full load of fresh oil, button it up, rotate compressor, vacuum, and recharge. Works every time.
If you cannot return any reused part of the system to "like new" cleanliness, it should be replaced.
For just leaky compressors such as a Gm bellyleaker... I check the tube, if its good it gets a new tube, new not rebuilt compressor and dryer.
Pretty much the same for bad clutch bearings and other non fatal problems.
Locked up, metal in the tube, scroll with a hole etc gets new compressor, dryer, expansion device condenser and a flush.
If a customer does not want to do it correctly I charge them my $65 diagnostic fee and send them away.
My Civic has 170k miles and the air conditioner no longer cools at all at idle, but cools just fine at 1500rpm and above. The dealer informed me the compressor needs to be replaced. I intend to do the replacement myself and I have a few questions. Since the compressor has not failed catastrophically, can I get by replacing only the receiver/drier and compressor? A lot of places recommend replacing the valve block and even the condenser along with the compressor. My thinking is that the system should still be relatively clean since the compressor still works off idle. Any opinions? Another question concerns the amount of oil that should be in the compressor. The Honda manual says to drain the old compressor and then subtract that drained amount from 130 milliliters and drain the resultant from the new compressor. How's that supposed to work? I would have thought that you would want the new compressor contain the same amount of oil removed with the old compressor. I would have thought that you would want to drain both the old and the new and then add back the same amount drained from the old to the new compressor. I'm confused. Can anybody explain how Honda's method works?
The Scroll compressor can wear and still function at higher RPM. You assume the system is clean, but where did the wear go? If this is the case, its now some gray crap that will be found in the oil.
The dealer "informed" you; was this with inspection and analysis? Did they verify air flow and fan operation? Poor heat rejection is also a common cause of poor cooling at idle.
The filter/dryer is definitely recommended. The expansion valve block can be cleaned, inspected and tested (or replaced). The condenser can be back flushed if you have the right equipment (or replaced). Most of how I would go about replacing this compressor in my first post in this chain above.
The Honda factory manual procedure is the "oil balancing" install. Warranty derived and based upon the assumption that it will be a fairly new virgin system. It has a high success ratio based upon the number of new cars you work on. It varies a little from brand to brand, and it can be confusing, but that's how it works. So is your 170K Civic a virgin?
Older systems just need to be properly flushed; read the compressor warranty.
Yes, I think this was the first time the system was cracked. I got the car with 90k miles and I've never touched the A/C before. The Honda dealer did a regular A/C service. He evacuated the system and then recharged it and ran it thru its paces. It was only a tenth ounce low. The mechanic said that the pressures at idle were almost equal and recommended a new compressor for $1550. The system still works great as long as the engine is above about 1500 rpm. Isn't the receiver/dryer where the system filter is? Shouldn't replacing that be enough? The oil is not cloudy and doesn't appear to contain any debris. As near as I can tell the expansion valve block is right at the evaporator and requires removing lots of stuff under the dash to get at. I'd like to avoid that. I intend to do the replacement myself, I have the tools and the know how. The only reason I took it to the dealer is, I don't have any recycle equipment plus they mailed me a coupon for only $29.99 for the system check.
The A/C system filters (accumulators and filter/dryers) are desiccant filters (to remove moisture) and while some do contain a screen (about 80 mesh), they are not fine debris filters. Proof of this is evident with the large amount of metal fines that are often flushed from a TXV system evaporator. Yes, you can do a new compressor, filter/dryer, and guess on the oil. I am just saying I would do a more; to give longevity more of a chance. Its about analyzing the risk of repeat failure. The cheapest route often just produces frustration, lost money, plus the added cost of doing it over again.
I get where you are coming from and thanks for the advice. The dealer certainly wasn't going to dig into the dash to get at the expansion valve body for his price which included over $1200 just for parts. I've got to balance the high mileage and vehicle age (it's an 02) against my investment, be it my time or money. Since getting at the receiver/dryer already requires removing the front bumper cover, the condenser will then be easy to isolate and flush. I think I will leave the lines and evaporator & valve in place, way too much trouble to isolate or remove. Will trying to flush thru the evaporator and valve in place via the lines do any good? Or does the valve restrict the flow to much to do an effective flush to the evaporator? More than 2/3rds of the oil will get replaced with the new compressor and receiver/dryer and flushed condenser.
Edited: Tue August 25, 2015 at 4:40 PM by Timelord
My 1988 Mazda B2200 truck. Compressor worked fine one day in October 2014 (Phoenix), seized the next day going to work. I bought new compressor from board sponsor, plus new drier. I bought flush and reverse flushed high pressure line backwards from the drier, line, and serpentine condenser and blew out all solvent with compressed air. Seized compressor contained zero oil, so full 6 oz of R-12 type mineral oil added (also from AMA), full vacuum pulled, vacuum leak test fine, added R-12 (24 oz. as per sticker.
2005 Yukon. I posted this, kept breaking belts, tensioner dancing. Fall 2004 GM TSB describer compressor being the cause, so even though cooling fine, I replaced compressor with new OEM Denso compressor about 3 weeks ago, plus new Gates tensioner, plus Deslugger timer accessory; since cooling was still great I kept orifice tube and accumulator as is. Still OK.
Edited: Tue August 25, 2015 at 10:40 PM by Cussboy
This is exactly the kind of advice I need. My pertinent automotive experience comes only from servicing my own vehicles over the years. I am approaching this from the viewpoint of a retired engineer who dealt with research vacuum and refrigeration systems for years. From the start I assumed I'd use a solvent that was easy to remove completely by evaporation. I have a small Welch pump with a base pressure of less than 10 microns and I have the luxury of pumping for a long time. I could probably put a turbo &/or a cryo on it and get to x10e-12 or higher but auto systems are o-ring sealed and low conductance. What I was not aware of is your implication that "traditional flush solvents" don't evaporate easily. I have only converted auto one system before and I used virgin MEK to double flush the each part of the system and then pumped it clean. To my knowledge that system is still working (I sold the car). This triggered me to look into solvents and it appears that flush solvent mfgrs don't like to list their ingredients. Do they contain high vapor pressure liquids? In that conversion, I was flushing out mineral oil, now I am flushing PAG, so some solvent research is in order. Is there a purpose made flush solvent for PAG that is completely volatile and still doesn't cost an arm and a leg?
My successful experiences flushing thru a TXV, followed with vacuum recovery; have been with HFC refrigerant solvents (perfect for PAG and/or POE). They can be troublesome to keep liquid (as they want to easily vaporize), especially if you are trying to blow them thru with air delivery. So we use a closed loop process with a pressurized solvent vessel and a vacuumed environment; to use the pressure differential to increase solvent velocity. Keep in mind all attempts thru the TXV will limit/negate any velocity you can apply. So this would be a oil flush (rinse) only, because there will be no energy remaining in the flow (thru TXV) to move substantial debris. The TXV has to be removed to basically power flush the Evap.
Many traditional A/C flush solvents on the market today will not offer any content info in their SDS sheets (claim trade secret) because (IMHO) they may/can/do contain cheap solvents, which may or may not be appropriate for A/C flushing. By doing so, they demand a premium price for a premium A/C flush. You get the wool pulled over your eyes, and they get outrageous margins. This is something I have been working on for 10 years with the SAE, and we are now finally discussing and developing a minimum A/C flush performance criteria standard. The boiling points are usually high and "if" you can get it all to vaporize, it will take a generous and long dry air blow (cannot do that thru the TXV).
As a traditional A/C flush, we manufacture the SAFE-FLUSH trademarked product available from this site sponsor. We provide chemical names and CAS numbers in our SDS (we may withhold the exact percentages). It is a blend of petroleum distillate and citrus distillate. Although Ford Climate Control Engineering and I may differ on formulation percentages, these are the exact same ingredients in the Ford approved Motorcraft A/C Flush. It is effective/miscible with all refrigerant oils (Mineral, AB, PAG, POE, POA, etc.), will not harm or react with the metals or elastomers, and has a long successful history. No wool here. But the BP is near 300 degree F and it does require a generous air blow to dry out to negligible trace levels. This just is not going to happen thru a TXV. Trying to remove this type of solvent with a vacuum pump will quickly dilute the vacuum pump oil and potentially damage it quickly.
I can easily put a cold trap in setup and stop anything from getting to the pump, but changing the pump oil a couple of times is usually easier. Thanks for all the advice. It may be a couple of weeks before I get around to swapping out the compressor (cooler weather has arrived in Albuquerque). I'll get back here then and let you all know how it went. Thanks again
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