Piston Slap: Test My HVAC, Read My Blog!

Sajeev Mehta
by Sajeev Mehta
piston slap test my hvac read my blog

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!


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.

Join the conversation
3 of 14 comments
  • Claytori Claytori on Dec 03, 2012

    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.

  • SupaMan SupaMan on Dec 17, 2012

    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.

  • Vvk The expansion of Tesla Supercharger network has been astonishing. They are popping up everywhere. Still nowhere near enough at busy spots especially in densely populated areas like NJ and California.
  • Kwik_Shift Equus paved the way for Genesis luxury
  • SCE to AUX "...memories of those shoddy Excels faded."Not really, since such comments appear in nearly every article about H/K cars.As for this one, who knows... maybe the 2nd owner ran it 40k miles without an oil change and destroyed the engine, then balked at the $10k replacement cost.
  • ToolGuy Last ad: Is that The Dude doing the voiceover at the end? 😉
  • ToolGuy Nice paint!!Too young to die.