AC system maintenance / repair / recharge

Excellent, detailed post, Lech.

@Mendel Leisk: leaving it up to the pros would be great, but I think true professionals like @lech auto air conditionin are extremely rare. If I had a guy like Lech that was local, I'd just bring it to him and pay up. But I don't and nobody has more interest in maintaining my car than me. I think there is a greater risk leaving this job to the local "pros" than learning how to properly do it myself.

Moving on to the next step: I ended up purchasing a Testo 550i Digital Manifold Gauge kit.

The seller sent me a manifold that is "nearly new" instead of new/unused. I don't want to contaminate my hybrid system with incompatible oils (PAG etc.), so I want to clean the manifold before using it on my Prius. Am I correct that even trace amounts of incompatible oil in the manifold is a legitimate concern, or am I going overboard?

I watched @lech auto air conditionin video on how to clean a manifold gauge:

I do have 99% alcohol on hand, but I don't have nitrogen. Can I blow out the manifold with compressed air and then pull a vacuum to remove any moisture, or is the nitrogen essential for cleaning the manifold?

 

Updating this thread 2 years later!

As detailed earlier in this thread, after I put in the UV dye, which also included 1 oz of R-134A, the system started blowing "cool" (not cold) due to the addition of the tiny amount of refrigerant. The driver of the car (not me) said it was "good enough" for them to drive for the time being while I carefully tried to find the source of the leak.

I searched for a leak with a UV light, but could not locate one. I did observe a tiny amount of dye on the schrader ports when I removed the caps to inspect, so I guessed that maybe the leak was simply from the schrader valves. I attempted to fix this by putting new caps on the ports.

Unfortunately, about a year later, the AC system returned to blowing mostly ambient air. I knew that I should evacuate the system, replace at least the schrader valves, and weigh in new refrigerant.

Unfortunately, I have been too busy with day job work to to do the fix until this month.

I will post a longer write up on the entire process soon, but for now I'm just trying to finish the repair and am posting this in the hopes someone has advice for me. ***paging @lech auto air conditionin ***

The short version is that I discovered a very small leak in the condenser via the UV light. I think the reason I didn't detect this two years ago is because the leak is small and it just took a long time to become evident. Photo below.



I replaced the condenser with an OEM Denso unit. I also injected 40ml of ND-11 oil. I also replaced the schrader valves and torqued them to spec. I pressure tested to 150 PSI with dry nitrogen and did not detect any leaks.

I pulled a vacuum overnight and woke up to see the image below. As you can see, the vacuum initially went great, reaching 72 microns. However, at that point, the system suddenly began to lose vacuum, going up to about 150 microns before I stopped the process to think about the next step. Subsequent vacuum attempts all began fine, but then flatlined at about 250 microns, even after leaving the vacuum pump on for over 24 hours.



My inexpert guess is that the deep vacuum opened up a weak link in the system and I now have a new leak. I tried replacing all the o-rings (with Nylog) in front of the evaporator (I don't want to take the dashboard apart unless I have to!), but I still can't pull below about 300 microns. Also, the vacuum plot now shows a constant ping-pong / up-down micron reading instead of a smooth line (image below). I think this is also evidence of a tiny leak that constantly opens and closes in response to the vacuum pulling on it. My guess is that this is either a leaking o-ring that I didn't replace (i.e., at the evaporator), or a pinhole with refrigerant oil covering it that continuously creates a bubble that pops and reforms.



I'm tempted to order *another* new condenser in case the one I just installed has a leak. I did notice before I installed it that there was some minor damage to the fins (photo below), but this didn't look too bad to me and I figured the nitrogen pressure test would reveal a leak if it existed. The nitrogen pressure test passed, but this was before I pulled the deep overnight vacuum. I have since performed another pressure test, and it seems to pass, but maybe I am just not detecting a tiny leak. The UV dye remains in the system, but I don't think I can take advantage of it for the new condenser because the oil has not yet been distributed through the system by the compressor.





Any suggestions for next steps?