Did my mechanic kill my AC compressor?


#1

I had an AC recharge done a couple of weeks ago and ever since the AC has been, well, loud. The sounds is sort of a grinding sound. I’ve heard it before a few years back when it died and needed to be replaced. Anyway, before I go accusing my mechanic of messing it up, I’d like to know if there is any way the recharge service could have caused this issue. I get that kind of accusation all the time in my field, so I don’t want to be that guy!


#2

Yes, it sounds like he did something wrong. When you recharge the a/c system, you have to remember to use refrigerant with oil and sealant to ensure a proper charge. You also have to ensure that you get it to the right pressure. What it sounds like is, they emptied the old refrigerant and didn’t put in the new oil… So yes, it sounds like he screwed your a/c up.


#3

Nate, if your AC needed to be recharged, the damage was already done.

Your car’s AC is, when operating correctly, a sealed system, so if it needed a recharge it means the system was leaking, and was no longer sealed.

Recharging the system does not damage it.

The damage happened as the system lost its charge, while you were driving.

There’s no one to blame.

Fix it or not, as you see fit, but stop looking for someone to blame.


#4

What should have happened is YOU the vehicle owner should have requested a diagnostic, and not a pump and go. Similarly as a mechanic, he should have refused to give you a quicky charge, and offered to do a more expensive service, but the RIGHT service, which tends to have a negative effect on the attitudes of cheap customers. AC systems don’t just need a miraculous charge every now and again as a matter of design. If the AC system needs a charge, it also needs a leak repair. Now, I’ve owned several vehicles where the rate of leak was less than one bottle of R134A per year, so I never bothered to fix it because it would just blow semi-cold by springtime.

In the absense of a vacuum system to test for system integrity, a “cheap” way (and less ethical one from an environmental standpoint) to diagnose system integrity is to charge the system to full capacity along with ultraviolet dye. Run the system, and the leak should be apparent rather quickly. I’ve had some repairs where I had to let the customer go, agreeing to run the system and come back in a week or two, or when the system stopped running cold, to allow us to find the leak and proceed with a repair. We had a US Marshall who had to sit in his vehicle for extended periods just FRYING without AC, and the leak was so slight coming out of a line joint that we couldn’t see the dye deposition until he ran the system for over a week, and it was quite small, but allowed enough refrigerant to vacate where the system wouldn’t work after a couple weeks.

Once the leak is found and repaired by component replacement, NOW you need to find a shop equipped with a vacuum system so you can bring the system down to a strong vacuum and hold it there for an extended period of time, this dries the system out and removes any water and water vapor in the system (remember high school chem: water boils at room temperature under a vacuum). Once this has been attained and the system is verified not to leak, NOW you go about the task of charging the system by an automated machine that can measure the precise amount of refrigerant, OR you can connect a set of guages to the high side and low side connections, and introduce refrigerant by cans until the pressures are within spec and the air blowing out of the vents bottoms out to about 40-43 degrees F as indicated by a thermal probe inserted in the vent.


#5

If the system was very low or out of refrigerant then the A/C system already had problems. Loss of refrigerant means loss of refrigerant oil also.

If a recharge was done then oil should have been added (and may have been) but the system was already on shaky ground.

Just curious, but let me ask this. Did the mechanic quote a proper repair price and did you refuse that followed by asking for a recharge and see where it goes?


#6

I find the entire post to be a bit nutty -one of those classic “I don’t know anything but I’m darned sure mad about it…”

You don’t even know what is making noise. I’d not be surprised if the “grinding” was from a worn out belt tensioner rather than anything to do with the AC itself. I’d also not be surprised if the appearance of the noise (or you sudden awareness of it) was completely coincidental.

There’s no point is “accusing” anyone of anything. Take the car back and explain what is happening. When you get word back about, just make sure to get a patient and clear understanding of what is going on. If you actually find out what is happening and something still seems fishy then report on the details of what the problem with the car is.


#7

Okay, I perhaps conveyed the wrong attitude in my original post… after a re-read I’m not sure how, but no matter. I am actively trying to avoid wrongly accusing anyone of anything. That’s why I asked the question here before bringing the car back in.

Anyway, it seems like the consensus is that if I needed a recharge, the damage was done. Fair enough.

When I brought the car in, I didn’t offer any diagnosis besides that the AC was only working intermittently. This was one of a few things that were wrong, and my mechanic offered up all of the diagnosis and suggested fixes. I accepted what he suggested, so didn’t try to take the cheap way out. I suppose the grinding could be something else, but I can toggle it on and off with the AC button, so I think my assessment is reasonable.


#8

The last time I needed AC service I didn’t go to my regular shop. There is a shop in my area that specializes exclusively in automotive HVAC and I went there. You might want to take it to a place like that.

You didn’t say what kind of car this is, but the AC compressor is almost certainly driven by an accessory belt that has an automatic tensioner. A weak/old tensioner and/or stretched belt can easily result in tensioner rattle when extra load is applied to the system - i.e. whenever you turn the AC on. You could probably figure that out yourself by just watching the belt/pulleys as someone cycles the AC on & off.

Since it is only related to AC on/off the other thing one would look at would be a compressor clutch problem.

It is possible to damage a compressor through refilling if one allows liquid refrigerant in through the low pressure port. But any shop that recharges the AC with proper equipment would not end up doing that. This would most likely be done by someone trying to do a DIY AC refill.


#9

What make and model is this vehicle? I have seen many GM V-6 and V-8 engines get very noisy when the AC was turned on and found the cause to be a loose or missing nut at the power steering pump rear brace. Many AC compressors have been unnecessarily replaced due to that loose bracket.