HELP Need A/C Advice... Gas Blowing off???
 

I'm having A/C problems with a 2005 F350 Crew Cab Diesel Dually. It is blowing out the freon (Or whatever it is) and this blowout sounds like a tire blowing - big air escaping noise and a cloud with a mild chemical smell. This has happened twice to me when it has been idlying for only a couple minutes at cold engine startup. I have been beside the truck when it blows off and the noise is such that in makes you want to duck - it is significant. Once when being recharged and tested the high pressure has gotten up to 400+/- before the cooling fan kicks in, then the pressure goes down to normal ranges so I am told. This blowout has happened 3 times requiring recharge and the A/C output is greatly diminished after the first blowout and after the second blow on a charge there is no cool output at all.

I have been told by a local repair shop and one Ford dealer and that there is a "pop off/over pressure valve" in the system for overheat/overpressure. The local repair guy suspects a sensor or something that is "maybe Ford warranty" so he recommended I go to a dealer. The local guy also suspected a plase where he could look inside to see if it was junked up but said it might void warranty if the cause was a warrantyable item. The Ford dealer in Florida couldn't find anything wrong with the system or fan switch or sensors - he charged it up and tested it all day.

So then 5 days later the wife drives to VA and doesn't get out of the state before it craps out. The VA dealer has found (with a dye test) two leaks (Manifold Line and Evaporator leaking) and says there is no such thing as a "pop off valve".

The pregnant question is where does the blast of escaping gas come from and then with that amount of gas escaping there must be a significant hole somewhere, how does it hold a charge for 5 days or so.

Have I blown up / over pressured the system? Is there a temp/pressure sensor that kicks on the electric fan or a sensor in the Compressor itself? Does it sound like a blockage somewhere? I am afraid that the leaks are a result of something greater and repairing them will just set myself up for a second repair. I live in FL and need the A/C.

Any and all help or advice is appreciated.

Richard

Wow, you must be talking to the elephants... for the anwers you are getting.
Just kidding..

There definitely is a 'pop off valve', but it may be called something else. It is a spring loaded valve on the manifold where the high and low pressure hoses are attached to the compressor. It will have a hex head with a hole drilled right into the center. Most times when it opens, you will get a foam oil bath splattered all over the engine compartment.
It should not build up that much pressure. There is a HPCO high pressure cut off switch that is supposed to de-energize the compressor clutch when pressure rises above a certain amount.
You get high head pressure when there is not enough condensation, or enough air flow over the condenser, or your system is overcharged. You can also get high pressure when there is an obstruction in the system, preventing the refrigerant from flowing.
Older Ford systems had self-destructing compressors that would sludge up the condenser with 'black death', a compound made up of burned oil, teflon and eroded aluminum piston material. It would cause the pop off valve to blow intermittently.
I would suggest that you have the system evacuated, and have the condenser checked for contamination causing blockage and high pressure. It is very difficult to clean a condenser successfully if it is full of crud.
You should ask them to check the pressures on the low and high side, as your compressor may be deteriorating.
tom

+1 on everything tomw said. I'd like to add a bit more.

The High Pressure Cutout Switch "should" disable the compressor before the pressure relief valve blows. If not, the spring in the valve may be weak or the HPCO is defective.

Your High Side pressure is spiking until the electric condenser fan kicks on. Does the truck also have a mechanical fan and fan clutch? If so that is likely the root of the problem, the clutch has failed.
If you don't have a mech fan, the electric fan is not coming on soon enough. The system pressure should never go to 400+ before the fan engages. If you only have the electric fan, they usually run any time the AC compressor is called for. The system can't dissipate heat with no airflow over the condenser.

Because of multiple "blowoffs", there is no way to gauge how much oil is in the system. If oil was added to compensate for loss, there could be way too much oil in the system. This will also cause excessive high side pressure.
You need to find the cause of the poor airflow, have the system flushed to remove all of the oil and start at "0" with the proper amount of oil and refrigerant

Did you ever find out what the problem was? My truck, 2006 6.0L, is doing this very same thing and the entire a/c system has been replaced twice. After the first time I took it back to the guy that did the work, local tech from ford, and When we opened up the system the office tube had been sucked all the way up into the elbow just before the evaporator. Moved 2-4" downstream. We attempted to replace the office with one from the local parts house and recharge the system with the same results. This time the office tube became lodged so bad that we could not get it out. Ultimately he said the compressor had failed and contaminated the system and plugged up the office tube. I am not so sure as the office tube looked pretty clean to me compared to what I have found online.

I was able to get the local parts house to warranty everything since we had replaced the entire system, After replacing everything the system worked ok the air coming out was cold but not as cold as I would expect. I drove the truck for 3 weeks and one day while driving it I came to a stop at a red light with the ac running, after idling for several minutes I heard the system start to release refrigerant. I quickly shutoff the ac and then turned it back on a few minutes later it ran for a few minutes before I stopped again. After idling several more minutes it began to blow off refrigerant again. I am at a loss for what to do. I was hoping I could find out something online but this seems to be a pretty isolated issue.

Any and all help is appreciated.

I doubt the orifice tube could get sucked up towards the evaporator. There is just not enough vacuum to do so. The LPCO switch should de-activate the clutch winding, turning off the compressor, when the evaporator pressure(boiling point) drops below freezing. If it did not, you would have the evaporator turned into a block of ice... Just not enough there to do it.
Either the low side line with installed FOT was defective or the high side pressure is too high, which could move the FOT.
If you have a 'blowout' type sound, it is likely the high pressure relief valve. On older systems they were attached to the outlet fittings on the compressor. A spring-loaded ball bearing was pushed tightly over an outlet, keeping the refrigerant in place. Once the design pressure was exceeded, the spring moved, allowing the ball bearing to move, releasing refrigerant.
Back when 'Black Death' was killing systems, material got into the condenser and could not be cleaned by flushing. The gunk would migrate as the refrigerant flowed past it, and end up clotting the system. The high side pressure went through the roof, and refrigerant/oil would spew from the relief valve, leaving an oily residue underhood.
If the pressure gets to 400+, there's a blockage. The condenser fan should be running way before the pressure gets that high. The HPCO switch, if equipped, should disable the clutch and relax allowing the compressor to quit, and the pressure should drop.
I would be checking the condenser fan system. Dunno what controls, but they should kick on, I think, when the vehicle is standing still and the A/C engaged. Right now, from the get-go.
Oherwise, any heat taken from the passenger compartment will be dumped into the condenser with no where to go.. pressure would rise.(as it does...) as the compressor works harder and harder.
You are losing refrigerant as the relief valve opens, which will reduce capacity, and reduce A/C effectiveness. Get low enough and the compressor will short cycle, or fail to cycle for more than a few seconds. You are also diminshing the amount of lube supplied to the compressor as the refrigerant carries the lube. No refrigerant flow or reduced flow will also reduce the lube to the parts.
Fix the fans and likely things will work ...
tom

After the first compressor failed I doubt you achieved a good flush to clean all the crap out. You say everything was replaced, how about the condensor? Some are a micro-passage style that easily holds junk when flushed. It has to be replaced. Flushing a "black death" situation or one where the compressor threw a rod takes a lot of cleaner. We're talking a gallon blown threw backwards under pressure.
Take a look here for additional education. AC repair

same dam problem. It happened about a yr ago a few times but stopped. Blew the engine on 07 f550 6.0 and I had it replaced. Having major loss of power problems but that’s whole another subject. Now just this week the same thing with AC happened again. Blowing off coolant. I checked the system and charged it to the correct levels. Question and video posted below. My ac fan clutch kicks on and off but when i have the ac off and check the pressure on the low side its always in the red around 110 or higher. When I turn the AC on and the clutch kicks it goes back into the green. It’ll shut off then the gage will back up into the red and soon as it hits 110/120 again the clutch will kick back on. What’s the pressure suppose to be with ac off and also why does it only kick on when pressure gets in the red.

see above message but here’s video

it’s
https://cimg7.ibsrv.net/gimg/www.for...baa297444b.jpg
https://cimg1.ibsrv.net/gimg/www.for...8c24ed242c.jpg
blowing from somewhere here

without proper AC manifold gauge set, you have no idea what your system is doing. the "gauge on a can" is as useless as teets on a bull.
my bet is your system is undercharged.
but again, without knowing both low and high pressures and ambient temperature when running, that is gust a guess.

you don't have enough air flow thru your condenser check your fan clutch. And it does have a pop off valve it is on the manifold . Driving it should be good but idle stopped it will build to much pressure. There's a pressure switch on the pressure line just above the Compressor you will want to check that also

That post was from 13 years ago...

same thing keeps happening to me and nobody has an answer. Please help. Did you find out the problem.