Has ANYONE had an evaporator coil fail? I hear it's extremely rare, but my AC tech has said it's the evaporator because his 'sniffer' registers refrigerant out of the cabin vent. Replacing it requires a complete removal of the dash components (nice design, GM). I am loathe to do that, more because removing a dashboard and center console is something that I've never wanted to have happen, than the $3,000 cost (did I just write that??? lol) I'm getting a second opinion, but thought to would ask y'all. Thanks.

 

I had one a/c part failure on my C6 - low side pressure switch. No a/c issues on my 2016 C7. The a/c gets a workout in the metroplex.

 

On a previous car, yes. Dash has to come apart. Royal PITA that I didn't want to deal with.

 

If the sniffer detects freon at the vents or drain tube the evaporator core is leaking and would need to be replaced.

Dash needs to be dissembled to get to the evaporator.

Sorry, there is no quick fix for this problem.

 

I'm not sure how much of the dash needs to be removed beyond what I had to take out to get to a faulty Infotainment screen/unit but there's probably more than one YouTube out there on what has to be done. Getting the screen out involved removing just about everything to the left of the console and the console too. It might be possible to remove what ever else is necessary to get to the evaporator and drive the Vette to the dealer/AC specialty shop and get the replacement/recharge done and reassemble the dash yourself saving tons of $$. Sounds scary, but I studied the videos over and over and took my time and went easy on all that plastic trim but I "got 'er done" with minimal tools (7mm socket and plastic trim removal tools from HF). I was able to move/drive with the dash trim off but I'm guessing you'll need to pull the start/on/off switch and the HVAC switch from the trim panels but it's not that hard!

 

Well that saved me from getting a second opinion from my local shop!
Thanks.

 

Be wary of that diagnosis. There are a lot of things that can cause the detector to trigger. Many different gases, vocs, plastics, solvents, even high humidity. I would make sure that they do a bubble test at the evaporator to verify there is indeed a leak.

a more detailed explanation from google AI.
Halogen leak detectors, particularly heated diode types, often trigger false alarms from
non-refrigerant compounds containing chlorine, fluorine, or hydrocarbons. Common culprits include VOCs from cleaners, solvents, paint, adhesives, cigarette smoke, hair spray, and engine exhaust. High humidity, moisture, or oil on the sensor tip can also cause false positives

 

False positive?

Depends on the quality of your detector / sniffer.

HF yes.

High end no.

 

My brother had an HVAC business, for which I joined him for a few years after I got burnt out on the travel from my career. I was able to add some expertise with leak detection, since I was involved with a many projects involving gas leak detection even those that use helium gas. We got the industries best detectors and still there were many false positives. The best IMHO were the infrared detectors, but you had to be pretty close to the leak. The heated diode style always gave false positives. Guys would stick them in a plenum, or around the armaflex and claim there was a leak in the evaporator. We always made them find it with an infrared, then verify with bubbles. We made very few mistakes with that method.

 

Every time I used a freon gas leak detector It never lied to me. It was a high end one. Wish I still had it but the Lab wanted it back. Never bought one for myself due to the high cost, remember this was a lab quality leak detector, not HF.

As for using the bubble technique first you have to get to the evaporator, pull the dash, and if the leak is small you'll never see any bubbles.

As for the Helium leak detector the one I use in Texas Instruments Central Research Lab cost over $15K, and I doubt that it would be practical to use on a car, you also need a tank of pure Helium. They also had a Hydrogen leak detector, even more $$$, and it would detect the smallest leak being that a Hydrogen atom is smaller than a Helium atom. But it was dangerous to use so everyone just used the Helium or Nitrogen gas detector for leaks. all this equipment was use in systems that require a very hard vacuum ie: 10 to the -6 torr and lower, depending on what you were working on.

But in practicality most HVAC pro's use just nitrogen gas to pressurize the system and use a nitrogen sniffer or if its a big leak use bubbles.and after repairing the leak then pull a medium vacuum by pumping the system down to < 500 millitorr and watch the gauges for a rise in pressure over time.

Bottom line is to buy the best leak detector you can afford and use it properly.

 

I agree with most of what you said, except not finding the small leaks with bubbles. We had found leaks as slow as every 2 years with bubbles. Even some equipment manufacturers submerge the coils into a liquid as a test for leaks. You still cannot put the sensor into a plenum, and claim that there is a refrigerant leak, especially on a car that has been assembled with so many solvents and plastics that for the life of the vehicle are producing VOCs.

One of the manufacturers we worked for built Ultra Low Freezers, Baths, and Cryostats. Cascade refrigerant systems that had to be pulled to <50 microns for 24hrs. In the lab it could be done, but in the field it was almost impossible.Nobody really liked working on them.

I am just saying that if it were me, I would check and double check every connection, joint, seal, etc where there is a more chance of a leak. Obviously an evaporator coil can leak. There was a coil mfg that was stretching the u-bends too thin and they had a high failure rate. I would try dye before I ripped the dash apart.

 

Seeing how ROYAL of a PITA it is, I would agree with double checking every inch of the system before going on with ripping out the dash. I'd hate to do that only to find it still leaks somewhere else instead. Dye would be great to eliminate the outside area.

 

Have a tech check around evap drain hose with a UV light for traces of a colored dye.

AI OverviewYes, C7 Corvettes use ultraviolet (UV) leak detection dye in their air conditioning systems from the factory
.
Here are the key details regarding the C7 AC system and dye:

• Factory Applied: Similar to many modern GM vehicles, the refrigerant in a C7 is typically mixed with a tracer dye to help identify leaks.
• Leak Detection: Because the AC system is sealed, low refrigerant is almost always caused by a leak. A "sniffer" tool or a UV light is used to find these leaks, and the dye will glow under UV light at the site of the leak.
• Common Leak Points: The most common locations for leaks in a Corvette AC system are the high and low service ports (Schrader valves), the condenser, or the compressor itself.

 

^^^^^
Since the info is AI generated, it could be exactly correct or total garbage.
Further checking is appropriate.

 

If it is correct, it would be a smart thing for them to do. I know it is GM, but hey, it could happen.

 

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I am assuming that you had some AC problems and they found it is low on freon. How long has it been since it was topped up? Just thinking if it needs freon once per year, heck just fill it up.

 

If you are going to sell it tomorrow that is an option. I would not want to do it for a long term solution.

 

I appreciate all the advice. And, yes, it's been recharged but the refrigerant is gone after 1-2 days. It's been sniffed, and the sniffer detects refrigerant from the air vents but not anywhere under the hood. So, as many said, it's likely the evaporator coils. BUT, could some leak somewhere near the engine-side firewall make it's way into the air intake for the air vent, and thereby be detected by the sniffer at the air vent (maybe the guy's sniffer didn't find that particular leak)?

 

When using a sniffer:

On evaporators, Freon really 134A or 1234YF, is heaver than air, thats why it first shows up on the drain tube.

Also shows up at the vents when the fan is first started which blows it out from the evap chamber.

UV light is the easiest and cheapest way for most and a good starting point. Only shows up on the drain tube and not the vents. Also shows up at all the under hood AC components.

In the 'old' days we would just add a can of R12 and watch for the bubbles to disappear from the sight glass on the receiver. Back then R12 was less than $1 a can so it made no sense to troubleshoot the system any further if the leak was small. Also manufactures made R12 with red dye that was visible to the eye, no need for a UV light, but it made a real mess at the leak point.