Last summer I replaced the dead AC compressior in my 1978 244 and converted to 134a. Used it quite a bit, and it worked great. Cold! Started using it a few weeks ago, and fired right up cold again. Amazing nothing leaked over the winter. Probably used it a few times over the last few weeks.

It was a real scorcher here today (98F). While waiting for my wife to come out, I was idling the engine and turned on the AC. Could hear it really working hard. Not two minutes later, there was a huge explosion of refrigerant from under the hood. Sounded like a shotgun blast, and a big cloud of spray billowed out through the grille.

Shut the engine down immediately and popped the hood. Oily refrigerant all over the hoses. The A/C hose that disappears into the firewall was very loose; I didn't try yanking it out, but I'm sure if I pulled hard enough it would come through. The hose connections on the compressor itself were tight/solid.

Shut A/C down, and the car ran great.

Three questions:

(1) any idea what caused this?

(2) this ever happened to anyone else out there?

(2) How do I replace this hose/get at the component it hooks into?

Chris!

The loose hose going through the firewall is a RINGER! Pay little or

no attention to it!

If that hose had blown the mess would be inside the car, under the

dash. The broken hose is probably where the other guys said, between

the compressor and the condensor or between the condensor and the

firewall.

What caused this explosion ?

IMHO, the reason of the explosion was excessive high pressure. This can be caused by different reasons :

- Clogged expansion valve.

- Bad cooling from the condenser.

- Overload from R134a.

If your car has no forced fan behind the condenser, I expect the bad cooling was the reason. When idling, there is a very bad ventilation of the condenser, this raises the temperature in the condenser, and the pressure goes up with it. I believe there is no high pressure switch on these systems to cut out the compressor, so an explosion is well possible. Before you repare and reload the system, try to put a high pressure switch in the system to prevent this in the future.

your problem may have to do with the difference in pressures of the two systems. Most mechanics suggest a 80% fill only when converting to R134. I would suggest immediate (if not sooner) fix as the system is designed to work in a vacuum (ie. no air). You may choose to check out re-filling with freeze 12 which is a blend of refridgerants thaat move both oils around OK. THe advantage of f-12 is that is operates at more or less the same preessure as r-12. I have heard that 134 is quite toxic to the user so WATCH OUT when breathing and touching! good luck.

I would also assume that you are looking at dropping out the dash to replace the hose. Quite a bit of work I am told.

Chris -

Your Three questions:

(1) any idea what caused this?

R134a works at higher pressures and temperatures than does R-12 Freon. Hoses tend to age and get less flexible. Combine old hose made for R-12 with higher pressure, and you should be surprised that this didn't happen earlier.

(2) this ever happened to anyone else out there?

No answer here.

(3) How do I replace this hose/get at the component it hooks into?

There are two hoses that disappear into the firewall, one connected directly to the compressor, the other runs along the PS fender and connects to the receiver/drier which is just right of the rad. That's the one that probably blew, as it's in the high pressure side of the system. That other hose is low pressure.

You can get a new hose made up at a good independent a/c shop, using the old one as a template for length.

NOW - you lost all the refrigeration oil along with the refrigerant. You will need to replace the oil, the receiver/drier, the hose, the R134a and every O-ring you can get to. The O-rings must be the yellow variety for use with R134a. Before re-charging you should run a leak test to see if there is more leaks. I'm told that R134a molecules are smaller than R-12 and can therefore get out places that R-12 won't.

Good Luck :>),

Bob