A/C problem: 2011 GT 6spd

[Too40gawlf]

My car's bumper to bumper 3/36 ran out in May. The car only has 10.4K miles on it - about 4K of which I've put on in the last 90 days or so.

My A/C has started acting up. On normal, short drives, it works fine and blows cold just like it should. However, on longer trips, out on the highway for example, the A/C starts off just fine, but after about 20 minutes or so, it peters out till its not blowing any cold air. If I turn it off or run the heater for a few minutes, it will be fine and revert to blowing cold air again until the process repeats itself. The biggest clue as to what may be wrong was on a recent road trip, once the A/C petered out, I pulled off the road for gas, I popped the hood and observed a chunk of ice had formed on the two lines coming out of the fire wall from the heater core. By the time, I finished at the gas station, the ice melted and the A/C worked again for a short time before it petered out once again.

My question is this: based on the above symptoms, what is the likely cause of this? Is it a freon leak in the system? Is it just low on freon from normal operation and just needs a charge? Or is the fact that the lines froze indicative of a bigger concern in the A/C lines/system - perhaps a bad A/C condensor?

My concern is that I dont want to take this into the dealer and pay $1500 dollars for them to diagnose and fix a condition which Im certain existed before the warranty ran out (its just I never drove the car in an extended manner to find out there was an issue).

My car has a long history or warranty work, far in excess of what a 3 year old car with 10K miles should have to endure and I wont be surprised if this turns out to be another example of shoddy quality - except this time, Im worried about footing the bill.

Any thoughts?

 

[Too40gawlf]

I mean, I will definitely be taking it in to the dealer. But at most, Im only going to pay for them to diagnose it. If need be, I will have the system discharged and I'll do the labor myself. Im not about to pay through the nose for A/C.

Since I dont know much about A/C systems, I would like SVTP's input on possible issues before I take it in for the dealer to look at it.

 

[svt04cobra1]

Anyone can speculate on whats wrong but what you need to do is hook a set of gauges up to it and see what its doing. Might be a clog in the system. Depending on what the gauges say, evacuate the system and pull the shrader valve and look to see if there is any metal or debris clogging the valve. If there is then your looking at a new compressor and all the supporting AC parts IE evaporator, condenser, etc. Good luck!!!

 

[manolith]

I think that I have an idea as to what's going on. If its icing up like that you might have a bad low presure switch. It should be a sensor on the suction line. The cold line that comes out of the evap. I have not looked for it on this cars but there needs to be one so once the presure drops below 30psi or so it should open and the compressor clutch will disengage. If that switch is bad the compressor won't ever stop pumping and will eventually ice up after a short period of time.

 

[13BremboGT]

^^THIS

But it's not the compressor that freezes up, it's the evaporator in the dash. Especially when it is humid outside, it will turn into a block of ice and air can't flow through it anymore.

 

[Too40gawlf]

I think that I have an idea as to what's going on. If its icing up like that you might have a bad low presure switch. It should be a sensor on the suction line. The cold line that comes out of the evap. I have not looked for it on this cars but there needs to be one so once the presure drops below 30psi or so it should open and the compressor clutch will disengage. If that switch is bad the compressor won't ever stop pumping and will eventually ice up after a short period of time.

Hmmm, at least that sounds better than what svt04 was saying.

 

[Blazer707@TBR]

I think that I have an idea as to what's going on. If its icing up like that you might have a bad low presure switch. It should be a sensor on the suction line. The cold line that comes out of the evap. I have not looked for it on this cars but there needs to be one so once the presure drops below 30psi or so it should open and the compressor clutch will disengage. If that switch is bad the compressor won't ever stop pumping and will eventually ice up after a short period of time.

What???

If your low pressure switch goes out your compressor will not engage at all. Thats when the old paper clip trick comes into play to jump the connector to make sure its just a switch thats faulty.

Lines that are freezing up indicate a restriction.

You need to put a set of gauges on it and see what your pressures are. These cars do not have a orifice tube. They use a txv, and depening on where its iceing it could be the txv not working or plugged up.

 

[manolith]

Blazer you never seen a lps stuck?

 

[Blazer707@TBR]

Blazer you never seen a lps stuck?

Never.

Im going to have to stick with restriction since there is a block of ice around the txv going into the firewall.

The 6.0L trucks have had a tsb out for a long time with the same concern. At idle cooling will be ok. Drive and it will slowly get more ambient in temp. You will see ice forming where the orfice tube is. Pull it out and you will have dessicant from the reciever dryer on it causeing a blockage.

 

[manolith]

I have seen stuck lps not on cars but on hvac equipment. Its rare but it happens. But yea there could be a restriction but usually when there is a restriction the evap won't get enough liquid to boil thru the entire coil and it won't cool. But shit happens. I agree that gauges will make the issue more obvious and easy to catch. OP if you don't have refrigerant manifolds get a set on amazone or eBay with the 134 quick connects for cars. It will save you money in the long run.

Also cars have a screen before the metering orifice that you could have shit in it but you need to dump the charge. You should recover it but you might not have a recovery machine that you could use.