As I understand you don't see freon and though the last re-charge my Monte got had the dye in it, the dye is responsive to UV light and a goggle set. I really don't have a way of knowing 100%. This was done by process of eliminate (my friend that does have these resources at his work eliminated all items he is aware of, leaving this).

I just hope this solves the problem....

 

Generally if the evaporator is leaking with dye in it, you can see it with no UV light.

 

All of the dye that I have used in AC systems, you could see without the UV light and goggles. I hope that the Evap. was the problem for all of the work you did. Evaps generally don't leak in that new of a vehicle but who knows. I hope my 2004 MC doesn't get a leak there because I don't know if I would be willing to tear the entire dash out. I never have understood why they have not made an easier access point for Evaps and heater cores.

Wayne

 

My A/C went out about 2.5 years ago in my 05 S-Charged MC. I hope my issue is nothing like what yours is. If so, the A/C will stay broken. Working full time and what I do for work (Endo Texh) I really do not have the time nor $$ for a shop to do it.

 

I've never worked with a dye in any of my fluid systems, BUT, when my friend had his stuff from work at his house, he let me try the goggles and UV light, he said when injecting dye, you can usually see a hint of it at the shader valve, sure enough with goggles and light I saw it (without, no sign of it).
He is a professional mechanic as a local dealership and though I understand Evap cores don't usually go bad (it does not make sense), him and the guys he works with have done them (he said the GMC Acadia is a real pain for this job).

As for why the heater core and evap cores are inside the car, it's all about temperature (and as you had features like dual climate control it requires more pieces to make it happen). If your heater core is out side the firewall, one, you have to make room for it and two, it would be exposed to the cold climate (even with the engine heat to keep it somewhat warm) and road debris. The evap cores used to be in a case outside the firewall. I believe that was changed as the industry was preparing to switch from R12 to R134a freon. If you ever listen to people who drove a lot of R12 cars, they always say the R12 blows COLDER then the R134a. Well, by bringing the evap core INTO the car you remove/reduce heat soak from the engine and move it closer to the people who want the A/C in attempts to compensate for a A/C system that is not as chilling as the ones of days past. Plus with dual climate control, you now have to really centralize where the cold and hot air comes from.

That's at least how I have understood it as I've read about these issues. Don't take it as 100% accurate, I don't design cars and have not examined true design reasons.

 

In all of the AC systems I have repaired, I always use the dye that you don't need the glasses and light to see.

I know the reason why the heater core and evap are under or behind the dash but they could still make an easier way to access these from under the dash so you don't have to take out the entire dash to get to them.

On my 92 cavalier, you can access both the heater core and evap from under the dash.

This car also uses R12 and the AC is colder than any of my R134a vehicles including my other 92 Cavalier that I converted to R134a.

Wayne

 

There can be a lot of reasons they design these this way. Keep in mind, that Cavvy does not have dual climate control to throw into the complexity of it. I can change a heater core in a '94 Grand Am in an hour (pop out center console and a cover for the core, there it is, hardest part on a v6 is getting to the lines on the engine side of the firewall).

I'm not going to say they could make it easier, as this is an aspect of car design I don't even want to try and figure out. At least now the dash is buttoned up, next get some brakes rebuilt and assembled and I can take her out for a much needed ride (and soon a freon re-charge)!

 

Well, I finally got the Monte together and I've been driving it a couple of weeks now.

Just this past Sunday, I met up with my friend the GM Mechanic. He gave the A/C a charge and said all looked like it should. The weather has been too cool to justify turning on the A/C most of the days. Today on my ride home from work, I decided to turn it on (outside temp was warm and from sitting in the sun, the car itself was toasty).

I HAVE AIR CONDITIONING!! It blows cold, give it a couple to a few minutes and it gets ice cold.

Now, this does not mean I'm out of the woods. The A/C has had a history of holding a charge for a while and then crapping out. So, I just have to see if it works for the long haul
Hopefully it still works for the trip to the GM Nats!!

 

Remember, AC Freon has an oil in it. It's good to run it at least once a month whether you need it or not so the system doesn't dry out and crack on the rubber lines and such.

 

I have done a lot of heater cores in the past. I hope I never have to do an evap on my Monte after seeing this...

After you are done you can think of all the $$ you saved!