2017 Caravan - Air conditioner leak

I seem to have a leak in my 2017 Caravan's AC. The system got less and less cool last summer and eventually stopped working altogether. I went to look for leaks with a can of R134a + dye. I put in a can of R134a to make the system cycle and it does pump out cold air - colder in front than in back. Then I held the can on there for 3 seconds to put dye in. I cannot hold it upside down due to clearance issues, but it did spray some dye on the schrader valve.

However, I don't see any leak with the UV light at the rear evaporator (where it normally fails on these) or at any of the fittings. I even pulled off the whole side panel and pulled the tubes to be able to look right at it. I haven't gotten a look at the front evap, I don't know a good way into there. I also couldn't get a good look at the compressor.

I also got some cheapo leak detector sensor https://www.amazon.com/dp/B015FK1EH2 but it never went off, even when I was holding it up against the rear evap. I went over all the fittings I could find and all over the front condensor and no luck. I didn't get to the compressor, I just remembered. I tried all the vents, too, front and back. When I get to it again I can try the front condensate hose, but it's over a heat shield, making it a hassle.

What would you guys do next?

There's a block-off kit to block the rear if that's a form of testing I need to do. But at that point I'd probably just pay someone to diagnose and then I'll fix it myself.

FWIW the bottom of the evaporator looked wet. Is that normal?

Mine was leaking from both evaporators and the front condenser. I guess everything gave up at once. I replaced all of it, both expansion valves and the dryer included. Fortunately the compressor was ok. Parts cost wasn't too bad, I didn't spring for Mopar stuff but bought denso and gpd for the major stuff. The total was under $500 including the heater core, which I did because it has to come out anyway. It's been about a year and so far so good.

The job sucks. The dash is heavy, so get a friend to help you when you get to that point. If I were to do it again I'd probably pull the front seats too to give myself more space. Be careful with the expansion valve in the back, it's hard to get lined up and the lines are made of cheese so if it's not, you'll demolish one or both when you tighten it down. The repair for that is not pretty - fortunately I was able to reshape it sufficiently to seal again.

Do you have the orange uv goggles? They help a lot in seeing the dye. Other than that, finding the most powerful uv flashlight you can and checking it in the dark is all I can suggest. You won't be able to see the front evaporator with it in the car.

I've seen the valve cores leak, evaporator leak (the uv due colored water out of the drain is your clue here), the condenser gets a pinhole leak from road debris, and just the orings/gaskets leak.

So what I'm hearing here is I may need to get an official, professional diagnosis

Probably for the best, yeah. If you decide to do it yourself I have the service manual on cd, I'm happy to try to get it to you somehow.

Where I've landed with this is that I'm going to wait and see how much time I can get out of one of those recharge cans. So far I'm at ten days. Even if it were to fail today, extrapolating that out across the summer, that's only ten cans at worst (assuming nothing else changes), which is about $130. So that's totally doable. Better case is that one can lasts all summer. Here's hoping.

My rationale here is that I went over almost all of the system with the detector, with the UV light and goggles (and non-colorblind wife) at midnight, and even with a spray bottle filled with bubble solution. Finding absolutely nothing, my take is that the leak may just be too small to find and therefore not fast enough of a leak to warrant all of this work vs occasional refill.

Talking to a commercial HVAC friend of mine, his only other step (and his preferred, FWIW) is to fill it with nitrogen and listen/feel for leaks. But at ten days and counting with the recharge can, I think I'm good for now.

In reply to P3PPY :

I used to have a Prius where a can would last 4 weeks.  I got through that summer 4 weeks at a time.  

I kept the can and hose in the trunk.  Therefore, if it quit at any time, I could just rejuice it in any parking lot.