A/C "explosion"?

I have a 2000 VW Beetle. The a/c was fixed, but when I collected it, the cold air only lasted a day. I took it back, the mechanic said there had been a leak and it needed a new “O Ring” (I have about as much car knowledge as I do Irish clog dancing knowledge). Anyway, I drove the car for about 10 miles and was thinking how incredibly cold the new a/c was. When I got home and parked in my car port, a short while later there was a cartoonish sounding “explosion” (I even went outside half expecting to see the neighbors in the street). When I reversed out of the car port the next day, I noticed the debris of car parts under the car, including some black foam blocks (or now parts of) and some metal disc thing. And of course, you guessed it, the a/c does not work! What on earth is going on?

Something broke. Plain and simple. You need to have it looked at right away to make sure there is no collateral damage that will cause problems with the engine or transmission.

If you are unaware, the A/C system works my compressing the refrigerant to a very high pressure, about 275 psi, then letting it drop to a very low pressure, about 30 psi. Even at 30 psi, the sudden release of gas causes an explosion type sound. The system not on will equalizer to about 120 psi. This will cause a very energetic explosion if it finds a weak spot to break through.

Sorry To Hear About Your Explosion, Judith. You May Not Know Cars Or Irish Clog Dancing, But Your Writing Prowess More Than Makes Up For It. Other Than The Tradgedy Of It, I Enjoyed Reading The Account.
It was organized, entertaining, and very easy to comprehend.

" . . . there was a cartoonish sounding “explosion” (I even went outside half expecting to see the neighbors in the street)."
I couldn’t help but picture something involving Road Runner and Wylie Coyote. Thanks for the chuckle.

I’m just curious. are you a professional writer ?


“how incredibly cold the new a/c was”

I wonder if they overfilled it with refrigerant.

Overfilled would not be colder. It would actually be warmer. The system simply had a weak spot, and it finally gave way. I wonder if it was a rusted pipe or coupler that let go.

BustedKnuckles is right in that obviously something went completely wrong and you just have to get it back asap to have it dealt with. There’s nothing you can do about it - even if you knew all about car A/C systems you still needs special equipment to deal with anything related to the AC.

But I am curious. Did you actually pop the hood and look around? You don’t have to know what you’re looking for - you just look for something obvious. I’m also wondering whether you either took any pictures or might be able to describe the “metal disc thing” better.

I have seen AC systems “let go”. It is not at all explosive (espically when system pressures are equalized as they are when the AC is off). What it looks like is a big release of steam that lasts about 5 seconds. The Beetle being a reciever/drier car (as the Germans are fond of) does not have a large amount of refridgerant in an accumulator to release quickly. I think this is another case of a “sparkplug that shot out like a rocket” as the explosion was only in the creative mind of the writer.

Thank you all…so far. Well, I did look at the engine, which was not in the least edifying. Look like an engine. But then I took some photos of the “bits” I had found, and then went to the Internet and searched for “1HO 820 692” and found another person’s post with an image. Here is what it looks like (but my foam interior is in many pieces!)

Also, the metal button/disc is copper colored, with a green rubber ring around the edge and a small hollow post protruding. It’s about a 1" diameter. It’s Sunday and I am terrified to drive the car and cause serious damage. Help…?

quote from previous link:

Some guy started a thread titled “Mystery object”, and he found this housing resting somewhere precariously in the bottom of the bay. Anyway, quote:

“Its insulation for aircon expansion valve. Indeed part 36. Less cooling from ac if its not on exp”.

“the explosion was only in the creative mind of the writer.”

No, I just told the facts as I experienced them, and I really did step outside as I was sure everyone had heard it. I will admit, it may not have been MY CAR necessarily that made the noise, that is to be confirmed–possibly a neighbor’s meth lab, who knows?

All I do know is I have bits of a a/c expansion valve on my carport floor and I am afraid to drive my car and cause irreparable damage.

WoW, you can identify an expansion valve by looking at bits and pieces but profess ignorance in all other matters related to the automobile? I am starting to sense a bit of a troll.

She realized it was likely part of the TXV based on the part number she looked up. I would go back to the place that redid the A/C, complain, and give them a chance to make it right, at the very least with a large discount. It sounds as if they may have overcharged it with refrigerant.

Dear “oldschool” Please refer to the terms and conditions to which you agreed when creating your account for this forum. If you don’t have anything nice/useful to say, don’t say it. I am having difficulties with my car. I know very little about how engines and a/c works, and so I turned to what I hoped would be a supportive, informative, educated forum. If you would take a minute to review the thread, you would see that I photographed the bits and pieces, found a serial number, looked it up on the Internet and discovered it was called an “air con expansion valve.” I do not know what this does and I am still unsure as to the seriousness of my driving the car now that this has fallen out. If you are sensing a bit of a troll, then I am surely sensing a pot calling a kettle black. If you have no further CAR ADVICE for me, then please refrain from responding to my honest request for help.

But thank you to “oblivion” who, unlike some people, has the ability to read and deduce, and the ability to offer practical advice.

If there are pieces of an expansion valve laying on your garage floor there must be a hole in the evaporator housing. I have worked for many years on AC systems fron the primitive to the very new and never saw a expansion valve break into pieces. When you are just refering to a number you looked up just say so, otherwise you are making me think you know what you are talking about. Now since you explained how you came to this part name I can assure you that what you are looking at are not pieces of an expansion valve(I thought you actualy knew what an expansion valve was). It is important to not try and give the impression you know what you are talking about as this helps no one.

As I have said for years, automotive A/C systems are not made to the highest quality standards. Seems like they put a cover on the expansion valve because they knew it was going to explode at some point.

A telling fact is the new refrigerant that will replace R-134a. This new stuff, (R-123XY or something like that) which costs 10 times as much as R134a and does not work as good is virtually harmless when released into the environment, which is where all automotive refrigerant ends up sooner or later…

If automotive systems were made to high-quality standards, we would still be using R-12 without any problems and expansion valves would not need plastic covers to catch the parts when they explode…

Oldschool says, “It is important to not try and give the impression you know what you are talking about as this helps no one.”

It also helps no one if you do not read the posts carefully. Even I have already understood that the black pieces are probably just bits of the housing/insulation for the expansion unit. I beg you, if you are interested in posting useful suggestions/advice please go back and re-read ALL the information I have posted (and click on the link to see the image I provided). Otherwise, please drop it. I will have taken it to a mechanic by tomorrow.

Judith, I followed every word you said and I find your descriptions to be perfectly clear and you should just be congratulated on your ingenuity to use the internet to look for a part number. Oldschool has his good points. But sometimes you just have to let him say whatever it is he says and kind of let it go. (Or argue ad infinitum about nothing).

Anyway, it seems clear that a bit of your A/C system blew for some reason. You can safely drive the car though you won’t have A/C. You do want to take it back to the shop that serviced it asap since your A/C system is now open to the atmosphere. The less it gets contaminated the better.

Thank you

It sounds like the expansion valve had a catastrophic failure. This is a very rare failure. Especially since the damage appears to be mostly to the interior, I’d suspect lots of damage to the evaporator coil under the dash.

The green rubber thing is probably and o-ring seal. The copper ring is probably another part of the expansion valve or the evaporator coil. The hollow post is probably a tube from the evaporator coil.

My vote is for an expansion valve failure. These use blocks that are different as compared to a normal expansion valve. My Merkur has one like this. Here’s a pic and note the disc in the one shot.


My first inclination was that the shop overcharged the system but this may not be the case.
If the system were way overcharged the A/C would not have been that cold going home.
The car was also parked and this means the A/C system pressure had stabilized with equal pressure on both low and high sides.
I think it was just age that did it in but that’s just my personal opinion.

What is great about this is that it did not happen while you were tooling down the road at speed. When an A/C system lets go there is a huge steam cloud that will disappear quickly but the noise and possibly the interior of the car filling with a dense white fog could have caused you to lose control of the car and who knows what then.
(The steam cloud is caused by the fact that R134 refrigerant boils at something like 20 below zero so you can see what will happen when it’s exposed to 70 degree temps outside.)