Frustrated with GM & Dealers' Service

[duder4thgen]

Originally Posted by Stingr69

The A/C system appears to be indicating low pressure. The evaporator temp will go down so low that the heat exchanger will actually collect condensate and it will freeze on the coil. The coil can get so full of ice that it gets blocked and no air goes through it. The air flow will get real cold and then start spitting out water drops before it totaly gets blocked by ice. If you shut it off and wait a bit, the ice will melt and you will be back in business until the ice starts to collect again. This is hard on the system if you keep running it while the coil is iced up so have the refrigerant pressures checked. You may have a leak in the system.

-Mark.

Originally Posted by jputer

On the A/C issue. R134A works at much higher pressures than the old R12. Sometimes hot, high humidity conditions will cause it to ice up the evaperator when you least expect it to. More of an ambient temp and humidity issue than a "low charge".

I'd say the answer for the A/C lies in-between these two posts. R134a actually operates at a slightly lower pressure than R12. Generally the pressure a refrigerant operates at is only relative to the saturation temperature of the specific refrigerant, they generally all exhibit the same behavior in different situations relative to saturation temperature (temperature liquid refrigerant begins to boil, with A/C this is always relative to pressure).

The causes for an iced evaporator would be either a low heat load or an undercharged system. Going to generalize a lot here to get the point across, usually for medium temperature applications you're shooting for the temperature of the refrigerant in the evaporator to be around 40*f, more specifically you're looking at the temperature of the refrigerant in the evaporator to be 40*f lower than the temperature of the air coming into it.

When a system is undercharged it will have a lower pressure than it is designed for, and that lower pressure will translate into lower temperature, which can cause the evaporator to ice up (to a point, too low of a charge will not be capable of exchanging heat). If a system designed to have an evaporator temperature of 40*f loses some refrigerant, the lower pressure can reduce the evaporator temperature to below 32*f/freezing, and cause the moisture in the air to freeze on the evaporator. If this were the case you would notice two things- for one due to the reduced amount of refrigerant in the system, there would be a reduced amount of heat that could be transferred, and the A/C would consistently take notably longer to cool the air in the car. Second, once cooled, the evaporator would freeze over on a regular basis. Seeing as how this happened once last summer on a road trip, I doubt it would be the case.

That leaves a low heat load. High temperatures will only prevent an evaporator from freezing over. Humidity can have an effect, in a specific situation. The air passing through the evaporator has a large effect on the condition of the refrigerant inside the A/C system. Warmer air will transfer more heat, causing higher refrigerant temperatures in the evaporator, and vice-versa for colder air. Like stated before, generally the temperature of the refrigerant in the evaporator will be 40* below the temperature of the air passing through it. So if you have 80*f air entering the evaporator, the temperature of refrigerant in the evaporator will be 40*f (once again this is a somewhat reliable generalization). This also means that if you have 70*f air entering the evaporator, the temperature of refrigerant in the evaporator will be 30*f, below freezing.

Now add into the fact that you're driving a 2010 Camaro- the interior is extremely well insulated, and the evaporator is equally as insulated, if not more. You were on a road trip in the summer from Atlanta to Dallas, don't think I'd be too far off to guess if I said you probably had the A/C blasting, with the air on recirculation (that's what I'd do). I'd be willing to bet the temperature of the air in the car was 70*f, if not as low as 65*f, to compensate for radiant heat from the sun. That means the temperature of refrigerant in the evaporator was from 25*f-30*f for at least a couple hours between stops. Add in the extremely high humidity you'll find between Atlanta and Dallas and that transfers into a huge amount of ice freezing on your evaporator.

What happened was most likely the nature of how your A/C system works, and if it only happened on a long road trip means that your car is very well insulated and your A/C is working correctly. The only way to prevent this is to bring warmer air in over the evaporator so the temperature does not go below freezing- turn off recirculation/max A/C to bring in some warmer outside air, or turn the temperature control slightly up to warm up the recirculated air. Another thing to consider is radiant heat from the sun. Radiant heat does not heat air, but it does heat up surfaces inside the car, including your clothes and skin, so sunlight will make you feel like it's warmer than the actual temperature of the air in the car. If you don't have window tint already, putting some on will reduce this effect and allow you to not adjust your A/C as cold and prevent it from icing up.

[eckerj]

Wow! That's a well thought-out reply! Thank you for taking the time to
generate such a great explanation..

I generally don't use the A/C unless it's absolutely necessary. Do you think
I would have experienced this icing if I had the temp control on Max but
the fan on one of the lowest settings? I seem to remember that I had
forgot that it was on the Max setting (the one that has an additional
click when you turn the temp dial counter-clockwise). I remember also that
the outside temp was hovering around 90 degrees.

If I read your post correctly, in high-humidity, high-temp conditions, the
evaporator can ice over quicker if I have the "recirc" on for extended
periods of time? In that case, it would be an easy fix. :-) Since as you say
the car is extremely well insulated, I can put it on recirc until it cools
off, then turn the recirc off. And keep it off "Max" :-)

Thanks again for your thoughtful reply!

[brtaus]

Originally Posted by eckerj

Of course, this is coming from the same region that makes people get out of their car for an oil change at a quick-lube.

Having lived in Indiana, Wisconsin, Kansas and Arizona, I have never been to a quick lube where I get to stay in my car while they do the oil change.

[duder4thgen]

Originally Posted by eckerj

Wow! That's a well thought-out reply! Thank you for taking the time to
generate such a great explanation..

If I read your post correctly, in high-humidity, high-temp conditions, the
evaporator can ice over quicker if I have the "recirc" on for extended
periods of time? In that case, it would be an easy fix. :-) Since as you say
the car is extremely well insulated, I can put it on recirc until it cools
off, then turn the recirc off. And keep it off "Max" :-)

Thanks again for your thoughtful reply!

The evaporator icing over is a result of not having enough heat load to keep the temperature of the refridgerant above freezing. So having the fan on low would deffinatly contibute to this- the less air flowing the less heat to transfer. A high temperature outside the car would keep the temperature of the refridgerant higher, the reason it freezes over is because the temperature inside the car is too low, so your evaporator would be even more prone to freezing if the temperature is lower outside. The more humidity the more moisture in the air to freeze on the evaporator, whether the ambient temp is high or low.

My advice is exactly what you said, turn the recirculation off on longer trips, try and find a happy medium to where you are comfortable, but not cycling the exact same cold air over the evaporator the whole time. And if you aren't going to be in the car for anytime longer than a couple hours I wouldn't even worry about it.

[eckerj]

Originally Posted by brtaus

Having lived in Indiana, Wisconsin, Kansas and Arizona, I have never been to a quick lube where I get to stay in my car while they do the oil change.

It must be a Michigan thing.... I grew up in Flint, lived in Detroit suburbs
for a while and was never asked to step out of the car and wait in a room
while someone changed my oil. I really miss the way they did things
up there. While still in the car, they'd change the oil, ask you to start it
back up, and show you the oil level before you paid.

[67 Convertible]

Originally Posted by eckerj

Hello,

Thought I would vent a bit here on the forums.

I own a 2LT that has a number of problems. I just got back from a
dealer's service department this morning. The end result is that
they will not service anything that they cannot verify.

Allow me to explain some of the problems:

1) After work last Friday, I begin my commute home and hop onto
the expressway. I'm cruising down the road and glance down at my
analog speedo to find it reading 140mph. Holy Smoke! I quickly check
the digital readout and find I'm at 70mph. I get off the expressway and
find a secluded spot, stop, turn off the engine and find the needle stuck
at 60mph. I turn it off and on again a few more times and it finally
settled in, stuck at 20mph. I drove home, let the car sit in the shade
a few hours, started the car and it's functioning normally.

I did read a few posts here about how the needles can be put on a bit
too firmly and with sufficient heat, they begin to stick.

Frustrated,

-Joe

There's a TSB that came out in June of 2009 for problem #1

#09-08-49-011: Instrument Panel Cluster (IPC) Needle(s) Stick Intermittently (Replace Instrument Panel Cluster) - (Jun 15, 2009)

I would ask why would it need to be "verified" if it's already a known problem? The TSB says it's "intermittent".

[Stl_chevy_guy]

I am now a Chevy salesperson but used to be a Service Manager for a motorcycle dealership and the theory is the exact same as cars. I know it is frustrating to be told that a dealer can't fix something that they can't see wrong, but you have to see it from the dealer's side also. If you went to work every single day and were asked to go on a wild goose chase for free because the customer and the manufacturer both would not be willing to pay for your work, then you would have a problem with that, right? Let's say that what you experienced one time a week before, and never re-occured, happened to be a fluke mishap. Then how do you think that tech that took your entire dash apart to get to your gauges to ensure your needle wasn't over-tightened, will get paid when GM says there wasn't anything wrong with your gauge.

Trust me, I know how you feel. I took my Charger to Florida on vacation and the car decided it just wasn't going to start for over two and a half hours at the hotel when I was trying to leave. Dodge sent a truck out to pick up the car that still would not crank or do anything. Once it made it to the dealer it started right up. They kept it overnight to ensure it would start the next morning again, while I paid for another night at the hotel, and it did so they made me come pick it up. They couldn't duplicate the problem and they weren't willing to run a bunch of time consuming tests on a car that ran just fine. I didn't like it, but the car never ever acted up again in the entire 33000 miles that I owned it. That happened at 8200 miles. Like I said, it may have been a freak mishap and it won't happen again. Unfortunately these cars are mechanical and that happens sometimes. But a dealer won't rip into a car to fix a problem they can't prove it has. I'm pretty sure you wouldn't have been willing to pay for the hours of work when they found out that there wasn't anything wrong would you?