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A/C help - Blew compressor discharge hose out of crimp. by Raydar
Started on: 07-05-2013 09:16 PM
Replies: 8 (666 views)
Last post by: Raydar on 07-06-2013 12:43 PM
Raydar
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Report this Post07-05-2013 09:16 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I alluded to my A/C system "explosion" in a couple of other posts.
I discovered that the high side (discharge) hose actually slipped out of the crimp, just after the "muffler" in the line. (Made a hell of a noise.)

What is likely to cause this? I'm thinking there's an obstruction somewhere. Please read on...

The last time I had the orifice tube out, the fluid was very dark, but there were no solids, and the tube wasn't blocked.

Background...
It's a 4.9 conversion. Uses the Caddy compressor. Everything else looks to be stock Fiero. There are no pressure switches on the compressor. The only compressor connections are to the clutch coil. Still have the low pressure switch on the accumulator.
When the compressor cuts off, the low side pressure seems to be extremely high. When it kicks on, the pressure drops to normal levels (well... before it blew the hose off, anyway.) Don't know if that's significant or not. IIRC, it's always been that way.

The system seems to have lost some efficiency over the years. Before I found a leak near the orifice tube, it has typically required a recharge every summer.
The compressor still dragged on the engine when it kicked in, so I have to believe it's working. Before the hose blew off, it was cooling fairly well.

Anyone?

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ltlfrari
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Report this Post07-05-2013 11:24 PM Click Here to See the Profile for ltlfrariClick Here to visit ltlfrari's HomePageClick Here to Email ltlfrariSend a Private Message to ltlfrariEdit/Delete MessageReply w/QuoteDirect Link to This Post
The switch on the accum is the cycling switch. I'm pretty sure you should have low and high pressure switches in the system somewhere if not on the back of the compressor. without them there's nothing to prevent the compressor turning on with a low charge (bad) or nothing to turn if off if the high side pressure gets to high (also bad as you found out). I don't know anything about th caddy compressor though so cannot really add anything else.

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Raydar
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Report this Post07-05-2013 11:44 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
The cycling switch also takes care of the "lack of charge". As soon as the system vented, the compressor shut off.
(I killed a compressor that was missing that switch, on an earlier 4 to V6 swap that I did. Been there. Was not pretty.)

I'll have to revisit my manuals, but I don't see any connections on that compressor, aside from the clutch.

Thanks!

[This message has been edited by Raydar (edited 07-05-2013).]

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Fierobsessed
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Report this Post07-06-2013 05:17 AM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedEdit/Delete MessageReply w/QuoteDirect Link to This Post
Compressors have an over pressure relief built into the back. It is centered on the compressor, Near where the hoses bolt to it and the switches (if equipped). It should have vented your refrigerant before hitting enough pressure that would destroy a hose, and of course your high pressure switch should have cut off your compressor long before that point. If your hose blew out, it was probably mis-crimped. Most likely, they didn't push the hose all the way in before crimping it. But the hose itself could have just failed at the crimp. Pretty rare and dangerous thing to have happen. Doesn't necessarily mean that you don't have a blockage. But since you have the A/C discharged, it won't be difficult to see if it is plugged up some how with a little testing.

Oh, and ALL GM A/C systems have some form of High cutoff switch, or 3 wire pressure transducer. They are usually on the rear of the compressor, but in later cars, they were put in the High line after the compressor, but before the condenser. So check to see if there might be an issue there.

[This message has been edited by Fierobsessed (edited 07-06-2013).]

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Joseph Upson
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Report this Post07-06-2013 06:26 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sounds like your system does not have a high pressure switch from what you've described. I'm not positive for some of the earlier compressors but my 06 model to my recollection does not have a pressure relief valve and with my swop I used a two spade hi/lo pressure cutoff switch to address the compressor not having any sensors built into it.

Two possibilities come to mind; your system is clogged from your description of the refrigerant oil color, or since you're in GA where it gets very hot, your cooling fan could be malfunctioning in terms of when it should be on relative to the A/C. If it doesn't come on soon enough your A/C high side pressure can go sky high very quickly when the vehicle is not moving. I had an intermittent bad fan relay that took me a while to catch as the motor didn't get unusually hot for a while to draw my attention to it right away from not sitting in one spot long enough.

I also turned the A/C on once while working on the car with the radiator removed (flushing the system with the water hose) and momentarily forgot until the A/C turned off (hi pressure switch activated) and I bumped the condenser and it burned me. It didn't take more than about 2 minutes or so for that to happen.

If you have a modified A/C hose it could have been poorly connected as was mentioned but I'd expect that to show up shortly after install as it happened to me and of course if the system is overcharged that can lead to it. I've seen the shark bite section on the OE Fiero hose fittings and they are not very aggressive at all, more like little ridges from what I observed and I remember reading something that suggests the relief valve may not open until pressures reach as high as 400 psi and that's if the valve isn't stuck and the compressor doesn't fail first or a hose. Gauges would tell if there is a problem when checking the system out.

[This message has been edited by Joseph Upson (edited 07-06-2013).]

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Raydar
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Report this Post07-06-2013 09:00 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Interesting.
The Caddy doesn't use a high pressure switch. According to the manual, it uses a high side temperature sensor that appears to talk to the BCM. The BCM then cuts off the compressor. (It also uses a low side temp sensor to cycle the compressor, the same way.)
Apparently, both sensors were done away with in the installs that this particular entity was doing. Only the pressure cycling switch in the accumulator is retained.
But yeah... Looks like the hose failed before the compressor vented.

FWIW, my fan comes on whenever the A/C is turned on. That was retained after the swap.
I was traveling at ~80 MPH, so the fan shouldn't have been an issue. The temperature was low-to-mid 80s, as I recall.

Also, when I disconnected the lines from the compressor, everything that leaked out was clear in color, except for a trace of green dye that I had installed a while back, looking for leaks (which I found.)

It looks like the entire line pulled out of the crimp. Well, the outside sheath, anyway.
The inside (layers) appear to still be inside the crimp. It looks like the hose just "delaminated". There is a possibility it was overcharged, but not according to the gauge on the (admittedly cheap) fill hose attachment.
At the very least, I plan to replace the accumulator (which I can't guarantee was replaced when the system was swapped and converted) and the orifice tube.
I'll flush out whatever I need to. Based upon the look of the compressor, the system may not be crapped up as badly as I first suspected.

[This message has been edited by Raydar (edited 07-06-2013).]

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Joseph Upson
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Report this Post07-06-2013 10:00 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
The orifice tube will give you a good idea of whether you have debris loose in the system, at 80 mph that condenser should have been pretty well ventilated and the A/C pressure on the low side of normal. Sounds like your hose is just worn out. Make sure there was no heat stress involved in the failure since that area should be near the exhaust manifold.


You can add a hi/lo pressure switch pretty easily now, it screws on to the high pressure valve in a "T" arrangement and you plug the dryer cycling switch plug into it.

[This message has been edited by Joseph Upson (edited 07-06-2013).]

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Marvin McInnis
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Report this Post07-06-2013 10:56 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

At the very least, I plan to replace the accumulator (which I can't guarantee was replaced when the system was swapped and converted) and the orifice tube.



That would be my recommendation, since you should do that anyway after the refrigerant system has been open to the air for any length of time. Inspection of the screen on the orifice tube assembly should tell you if you need to look further.

I would definitely advise installing a high-pressure cutoff switch, either on the compressor or somewhere else in the system. Or, being an electronics guy, you could probably figure out a way to use a temperature sensor mounted near the compressor as a surrogate for the high-pressure cutoff switch. Since you're probably going to be patronizing a professional hose shop soon, you might just have them add a fitting for a pressure switch to the high-pressure hose.

[This message has been edited by Marvin McInnis (edited 07-06-2013).]

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Raydar
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Report this Post07-06-2013 12:43 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Joseph Upson:

The orifice tube will give you a good idea of whether you have debris loose in the system, .... Make sure there was no heat stress involved in the failure since that area should be near the exhaust manifold.


The last time I pulled the orifice tube, the oil was very dark, but it was not blocked. There were no particulates, or metal, that I could tell.

Heat stress? Hmmm... My cat is in the stock position. The hose is not too far away. Not more than a few inches. It's a thought.
The hose just pulled out of the crimp. At least the outer shell did. Several of the internal layers were still in the crimp. Looked like the hose "delaminated".

 
quote
Originally posted by Marvin McInnis:
I would definitely advise installing a high-pressure cutoff switch...


Yeah. I have become painfully aware of that.

Thanks everyone.

[This message has been edited by Raydar (edited 07-06-2013).]

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