By on December 3, 2012

TTAC Commentator supaman writes:

Hey Sajeev,

Don’t have to say how much you and the B&B have helped me in the past with auto-related inquiries. Anyway, you need more material? Well here’s more. Up to perhaps a week ago, everything was fine on my STEED. I haven’t been using the A/C much because the weather has been much cooler but then it started to warm up. Got in the car to leave work and turned on the A/C to cool the car a bit and….nothing.

The air blows, but stiflingly hot air. After waiting for a few minutes to see if cool air would eventually surface i played with the auto-climate control and zoomed it down to 60 degrees….still nothing. Not having A/C is nothing new to me but quite annoying getting into a hot car. I took it to what was my usual mechanic (until the corporate GoodYear Service takeover) and their diagnosis was a compressor failure. Pardon my layman language but apparently some piece fell off the compressor (!?) that doesn’t allow it to engage once switched on. Also, because the compressor and drier (?) are usually built into one piece on my car (unlike others according to him) they have to be replaced together so I’m staring down the hole to the tune of $1300. With that amount of money at stake I’m willing to look for a second opinion (and a third). The mechanic did ask if I heard a loud *boom* while driving at any point and I can’t say I did. He also noted that several cars came into his shop for the same problem that week. Long and winded I know but could there be something else not causing the compressor to engage? A faulty fuse maybe?

Thanks as always: and on a completely separate note, you’re a car guy and so am I (otherwise I wouldn’t be writing you so often…lol) I started a car blog a few years ago and wondered if you could take a peek at it. I do it for fun mostly and share it with most anyone but since you’re more of a pro at this some pro advice would be greatly appreciated!

www.mytestdrives.blogspot.com

Sajeev answers:

Dude, I’m no pro. I do what I do: 13 years on the forums and almost 7 rant-filled years here on TTAC.

About your blog: except for the Aston Martin background (make it generic, low resolution and low contrast) your blog is good, and I’m not just saying that because I know(ish) you.  It’s good to see a personal blog with clever writing, good ledes and honest photography.  And you don’t seem to say crazy shit that’ll get your ass blacklisted out of every fleet after two months of getting free press cars…perhaps I’ve said too much.

Back to that tasty lookin’ Mazda 6: the part that fell(?) off the A/C compressor is probably the clutch.  I had one do something like that, and I simply gave up and let my mechanic install a new one, as I didn’t have the unique puller to do it in my driveway. It’s not the dryer, that’s normally a metal tube bolted to the passenger side firewall. Perhaps this infographic helps.

Your car is about 6 years old now, so depending on usage and mileage, needing a new A/C compressor isn’t totally ridiculous. But $1300 sounds a bit much, even for the real estate-challenged, labor intensive Duratec V6 model. Rockauto sells a remanufactured compressor with a new clutch for about $300.  And I wouldn’t be surprised if those vendors aren’t stereotypical aftermarket junk, rather their stuff is made (or re-packaged) for Mazda/Ford themselves.  I’ve seen it happen before on my Fox Bodies.

Odds are your mechanic diagnosed the right component, but get the breakdown on the labor hours and the cost of the part.  And always ask the shop if they will install parts YOU give THEM. That’s a good way to see if their profit center is markup on parts.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

 

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14 Comments on “Piston Slap: Test my HVAC, Read my Blog!...”


  • avatar
    DC Bruce

    If “something fell off” it’s hard to imagine that the drive pulley on the compressor is still on . . . but who knows. I have had a couple of instances where the electromagnetic clutch that engages the compressor fails. Apparently, heat is not a friendly environment for that. In one case, the compressor would work when the car was started cold, then fail once the car got warm.

    The price of the service strikes me as about 30% high, and I’ve never seen a dryer unit integrated into the compressor. I do not, however, recall being able to replace the failed clutch on the compressor, as opposed to just putting in a complete replacement unit. And it may be that having to open up the system to replace the compressor and then having to re-charge it with coolant, requires replacement of the dryer . . . or not.

    Seems like a second opinion is called for here, at least as to the cost of this work.

  • avatar
    nickeled&dimed

    “part fell off” sounds quite serious.
    When I had the AC stop working on my Subaru, I couldn’t tell what was wrong – the light on the AC button would not light up, and the electromagnetic clutch would not engage. I pulled the connector and jumped the clutch wire to the battery terminal while the car was running and *viola!* compressor turned! I thought it might be a relay or fuse too, after ruling out the clutch and compressor, but after forum searching and not finding anything wrong with said relays and fuses I finally took it to the pros (dealership). Apparently there is an interlock switch in the compressor that does not allow the clutch to engage when there is no refrigerant in your system. Leak fix and recharge cost $300. I recall the dealership saying if it wasn’t that, and was the compressor/dryer (actually I think relatively common to be paired) it’d be around a grand.

    • 0 avatar
      MBella

      The compressor is not part of the compressor but is usually replaced with one because the system has been open. Also replacing your thermal expansion valve isn’t a bad idea if the clutch failed because of compressor failure. Spin the inside of the clutch to see if you can freely spin the compressor. If it is really hard to turn the compressor has likely sent debris into your system and can get trapped in the TXV.

  • avatar
    PrincipalDan

    That picture just makes me long for that generation of Mazda 6 in either hatchback or wagon guise with the V6 5 speed manual combo. (Of course hard to find on the used market but not very expensive either…)

    • 0 avatar
      Dynasty

      With or without spoiler?

    • 0 avatar
      SupaMan

      I think I posted somewhere around here that finding this black beauty was quite the treat (and totally not what I was looking for in the first place). Loved the car ever since and I’m destined to keep her around for many rev and shift-happy years to come.

      Back to the AC though, I figured $1300 was a bit steep. I’m gonna take it to another shop to see if they can give me a second opinion and ask if the they’ll put in the part I give them, provided of course it is the clutch. I researched RockAuto (and Advanced Auto Parts) and found the parts are actually pretty affordable. Will keep you updated. Thanks for the help guys!

      • 0 avatar
        DrunkenDonuts

        A couple years ago I found an ’05 blue V6 5-door auto (don’t hate) that I absolutely love. I got it for under $10k from a private seller on Craigslist, of all places. Dealers were wanting $12-13k for same thing with double mileage. I consider myself extremely lucky for the find. Hope you get your issues sorted out. I’m at 75k miles now and the only thing I’ve had is the starter going out, thankfully.

  • avatar
    statikboy

    A question for Sajeev: do you personally answer all Piston Slap questions soon after receiving them, or do you wait until they make it onto the site to answer?

  • avatar
    claytori

    You need to get a second opinion and some more detail about what you will be spending your money on. The compressor is likely not engaging when you ask for AC. There can be simple/cheap and/or complex/expensive reasons for this. The most common cause is loss of charge (refrigerant pressure) in the system, likely from a leak or weak seal in the compressor. The next is that the clutch is not working. The coil could be burned out or some of these have a thermal fuse in them that can fail. A bad clutch can be easily replaced. A simple one I experienced is that the connector to the clutch wasn’t making good contact. Lastly, the compressor could have failed. But if this is the case it will spin, but not compress anything. This is the most expensive. As mentioned by the others, this can be rebuilt.
    These things should be easily diagnosed by your shop and they should be specific. That your shop is vague except for the high $ is a bit of a bad sign on their integrity.

  • avatar
    SupaMan

    So the second shop I went to over the weekend gave me a quote of $1400 (!). I then asked if they’d do the repair with parts supplied by me and they said no, some new policy came into effect recently regarding customer-supplied parts and insurance and liability and some other crap.

    Point is, I’m not paying that much.

    I’ve found a mechanic who’ll do the repair for me so hopefully I can get back to having some coolness in the cabin (it’s December and Miami is still hot as hell).

    Will keep you guys posted.


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