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Why does my car ac system keep blowing up?

Twice now my 92 Explorer has "blown" the compressor. In both cases it blew very shortly, within minutes, of starting the truck. It blew so shortly after starting the truck I have a hard time seeing how the pressure could be high enough to "blow" but in both cases it popped the high pressure relief valve and spewed oil and refrigerant out. The first time it did it I had started the truck, pulled out onto the street and immediately hit a red light. While at the light I put it in neutral and gave it enough gas to rev up the engine to 1500 rpm to run the compressor enough to get more cooling in the 100 degree heat. After less then a minute of waiting at the light there was a grunge/screech/smoke/smell and no more cooling. Seemed like the compressor had locked, oil blew, fan belt screeched over the locked pulley and the oil burned on the exhaust manifold. Then it unlocked but no more cooling. Upon tearing it down there was the expected "black death" look to the oil, it had about 100K miles on the system, and metal bits at the orifice tube screen. When I took the compressor apart there were broken bits and obvious new wear marks on the internals. I got a new compressor, accumulator, orifice tube and condenser and flushed the evap and all lines. Put it back together and it ran fine for 4 years.

Then last month I started it up after it sat all day, about a 95 degree day. Started it and just let it idle for no more then 1 to 2 minutes while I arranged my stuff before leaving. Then grunge/screech/smoke/smell and no more cooling - same thing again but I hadn't even sped up the engine. Immediately turned it off. Got out and looked, oil blown out all over the engine again. Turned it back on and the compressor spun freely, no funny noises, but no cooling. Unlike the first time, when I tore it down I didn't find anything much in the system, no little metal chunks, just a little bit of "blackness" to the oil, a small amount of sludge on the O-tube screen. The inside of the compressor did not seem to have any broken parts. From how everything looked I might have been able to fix it by simply recharging it but I had already ripped the compressor apart. So I bought all new parts again and redid it last week. Got a compressor, accumulator, o-tube and condenser from rockauto for $220. Now it's cooling fine.

Then about 3 days after fixing it I was at the SAME park where it had blown the second time. Started it up and heard what I thought sounded like the grudge noise - like the fan belt was just starting to slip and was fighting it. After having heard this twice before I immediately turned it off. Thought maybe, just maybe I smelled a tiny bit of burning oil but there was no smoke like the first two times. Drove about 3 miles to the store with the AC off and a frown on my face. Popped the hood and disconnected the compressor. Then started the engine and turned the ac on. Then plugged the compressor back in while I watched under the hood. Compressor came on, no funny noises, and it started to cool!! In fact, it seemed to be working perfectly normally. So I presume I caught it JUST in time before it blew out the high pressure blow-off again and spewed oil everywhere.

So at this point my thinking was that maybe I was putting too much oil in the system and slugging the compressor on start up. So I pulled the one week old compressor back off and checked the oil level. It was actually on the low side, certainly not at all overfilled. So put it back together and it's working just fine.

Sorry for the long post, ...

why is this system blowing up within 1 or 2 minutes after a "cold" start???? It's always in the 1 or 2 minutes when I would think the system isn't even working hard yet.

Every time I start the engine (and AC) now I have my finger ready on the AC on-off button ready to shut it off if I hear the slightest funny noise.

I put in 80% of the amount of R12 as I'm using 134a. Running it in the driveway at 2000 rpm I've seen the low side drop to 30 and the high side go to over 325. I don't see how they could possibly go even that high, much less to the 400 psi needed to pop the high pressure valve within 2 minutes after starting with the engine at or near idle speed.

Anyone got any theories? Too much oil? Too much refrigerant? Not enough virgins being sacrificed?

Reply to
Ashton Crusher
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Clogged expansion tube. Clogged evaporator.

--scott

Reply to
Scott Dorsey

My guess is that you're getting liquid refrigerant in the low side and into the compressor.

Reply to
dsi1

I know nothing about this particular vehicle, but if it uses electric coolant fans, the it's possible that the high speed fan and/or relay are either not working, or are intermittent. If intermittent, check the high current wiring to the fan - those connectors get hot, and start to fail. The relay, too.

If the fan is belt driven, you might have a bad fan clutch, but I'd expect the engine to run hot at times.

Check for obstructions in the air flow through the condenser.

Reply to
Bill Vanek

Evap was not clogged either time. Doesn't have an expansion tube, just an orifice tube. I guess that could clog but there is a filter screen before anything gets to it. Why would it do so immediately after starting and while idling yet never do so while running down the highway for hours on end?

Reply to
Ashton Crusher

You mean it's simply got too much refrigerant in it or do you mean there is something making the normal amount pool where it's not supposed to and then hitting the compressor? Can you think of any reason there would be a bunch of liquid refrigerant in the system when it's only been running for barely two minutes? Isn't all the refrigerant in a vapor state until the compressor starts running? That's what makes me scratch my head... it's failed twice, and nearly a third time, so shortly after it's started to run. It hardly seems like it has enough time to build up a head of pressure short of something literally plugging the system or slugging the compressor.

Reply to
Ashton Crusher

Those are good ideas. It doesn't have electric fans though and doesn't run hot. The condenser was very clean both times it failed.

Reply to
Ashton Crusher

Black gunk may be contamination... or due to compressor failure. Will assume the oil was correct type. First occasion could be due to not enough cleaning and purging.

2nd and almost 3rd, not likely. Were the oem hoses changed out for 134a hoses?
Reply to
Paul in Houston TX

Is it failing to cycle at times? Also, have you put gauges on it?

Reply to
Bill Vanek

BTW, did you evacuate the system after you opened it?

Reply to
Bill Vanek

Beats the heck out of me how liquid refrigerant could get into the low side hoses but the only thing that could lock up a compressor is mechanical damage or liquid in the compressor. Well that's my story and I'm sticking to it. ;)

Reply to
dsi1

Ashton,

. Why would it do so immediately

You have very little data so concluding that it's a "starting" phenomenon may not be correct. You may be jumping to a conclusion.

Dave M.

Reply to
David L. Martel

My '94 Saturn manual says if you don't run the AC for a few minutes every month, including the winter, the seals go bad. (who's gonna actually do that?)

Maybe broken seals-bits floating around? Not like I ever fixed an AC problem though.

Reply to
synthius2002

My guess is that seals going bad means that the O-ring will start leaking. I recently bought a $25 leak detector on eBay and found a leak in my AC in the flange that goes into the firewall. A couple of O-rings later, it was good to go. Thanks eBay and cheap Chinese labor!

Reply to
dsi1

SNIP

SNIP

SNIP

When did you do the 134A swap? After the first pop or the second? What oil are you using? Were ALL of the NEW parts shipped empty of oil?

If you are seeing 325 psi on the high side you have a problem. It sounds like a restriction on the high side. Possibly a chunk of crud that didn't get flushed out of the line.

Reply to
Steve W.

There is little data but all three times it was immediately after starting while idling. To me that would seem like the easiest part of the work day for the AC yet it overpressureized and "blew". I keep trying to figure out what there would be about the "refrigeration cycle" that would somehow create such a high pressure within a couple minutes of system startup. To blow off the high pressure valve it has to get to something like 400+ psi. Even with it sitting in the driveway as I finish putting 134a in it in 95 degree temps it only got to around 325 psi at 2500 rpm. At idle it's in the 200's. The only things I can see that would make it blow are a blockage or oil or freon slugging. I can see how a blockage could happen but if there is stuff in there that's going to block something it seems like it would have happened at high speed "the day before", not "today" when the system is just loafing along at low rpm's. Is there something about startup that would create an oil or refrigerant slug in the compressor?

Reply to
Ashton Crusher

I know one of them was as it had a muffler in it when it blew up 4 years ago and I had an AC shop redo the manifold with a new hose to replace the part with the muffler. It's possible the other hose on the manifold is an 18 year old one. From what I've read there is not supposed to be any problem with old hoses that have been well soaked with oil. But those two short sections are the only hose, the rest is pipe.

Reply to
Ashton Crusher

Serpentine belt. It's as tight as the belt tensioner makes it. So presumably no tighter then it should be but potentially loser due to the spring weakening. All the compressors were new. The only parts not new were the evaporator and two short pieces of hose. The hoses and evap were easily blown thru for flushing.

Reply to
Ashton Crusher

The 134a is what I used this last time. Time before that I used a "drop-in", ES12a that I have used in two other systems with no problems. But to eliminate the ES12a as a potential cause I went with the 134a this time. Yes, everything was dry except for the compressor. It supposedly had 7 oz (the full amount for the whole system) in it. I drained it to check and only got 5 oz out. So that left me with the question, did they only really put 5 oz in or is there 2oz trapped in the compressor. I went with the idea that 2 oz were trapped for determining how much to put in the system.

The 325 reading was in 95 degree outside temperature with the vehicle not moving, no extra fans, just the engine driven radiator fan, and at

2000 rpm. At idle speed it dropped to around 225. Will a restriction in the high side also cause the low side readings to be high? They were at about 30 when the high was at 325.
Reply to
Ashton Crusher

There is little data but all three times it was immediately after starting while idling. To me that would seem like the easiest part of the work day for the AC yet it overpressureized and "blew". I keep trying to figure out what there would be about the "refrigeration cycle" that would somehow create such a high pressure within a couple minutes of system startup. To blow off the high pressure valve it has to get to something like 400+ psi. Even with it sitting in the driveway as I finish putting 134a in it in 95 degree temps it only got to around 325 psi at 2500 rpm. At idle it's in the 200's. The only things I can see that would make it blow are a blockage or oil or freon slugging. I can see how a blockage could happen but if there is stuff in there that's going to block something it seems like it would have happened at high speed "the day before", not "today" when the system is just loafing along at low rpm's. Is there something about startup that would create an oil or refrigerant slug in the compressor?

What size of Vehicle or what make dose it utilize Expansion vale. dose it use electric fan motor, is it Mechanical directly hook up to motor. when Refrigerant was lost, did you find the leak is it on high side or low side. Have you Evacuated system before you added Refrigerant.. How much of refrigerant did you use, all systems are not same size. If your Vehicle is older then 1992 which means it is design for R-12 and not R-134, Sorry but that is the way it is!

Reply to
tony944

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