Automotive Air Conditioning Information Forum

I got this 2019 Honda Civic R last winter with a bad clutch and a transmission grind. Finally got all that fixed and started it up today only to find the a/c not working. Pretty sure it was working a few months ago. Anyway, gauges attached and show ZERO pressure. So I attach a vacuum pump and micron gauge. After 15 minutes, the gauge shows 320 microns. 15 minutes after turning the pump off, it's at 480. Vacuumed another hour and it's back down to 320 microns. Will let it sit overnight and see where it's at tomorrow. It's 95°outside today if that matters. Are those readings ok or do they indicate a leak?

As you probably know, you achieved a great vacuum on the system. The slight decline in 15 minutes might be due to outgassing of the oil and desiccant, the last vestiges of whatever contamination might have been inside the system. For the most part, since the vacuum seems to be holding (overnight will tell for sure), the refrigerant probably leaked out while the system was still under pressure.

Look for any visible signs of leakage as evidenced by oily spots, or possibly, UV dye if it has already been added to the system. Detecting the dye requires a darkened shop, a UV flashlight, and special glasses. If nothing suspicious turns up, add a few ounces of R-1234yf and then scan the system with an electronic "sniffer," paying particular attention to the dash vents, the service port caps, the plug on the bottom of the integrated R/D, and the compressor shaft seal area. If present, dye might also show up at the evaporator drain tube under the car.

Another 6 hours have passed and it's at 1400 microns. How much R1234 do I add to do a sniff test? It's almost $3 an ounce. Can I use R134 for that, since it will be removed anyway? Also have nitrogen but not sure how easy that would be for a small leak.

I am not sure about 134, I myself would prolly try that, John is in a better position to answer. Agreed it will all be removed. On a 134 system, I ‘puff’ it up to no more than 20 psi allowing 134 to enter both hi and lo sides. This uses very little Freon.

Remember that the Sniffer ( the best method in my book) will not detect nitrogen

2400 mircons this morning. Think I will try nitrogen and soapy liquid to check for leaks. If that doesn't find anything, I'll have to go to plan B.

Didn't find any leaks but nothing is really accessible. Charged it up with 15 oz r1234 and it's blowing cold. Hope I didn't just waste $45.

Good luck!
Keep us posted

I wouldn't recommend introducing any R-134a into an R-1234yf system to check for leaks. The US-EPA has mandated special fittings for R-1234yf systems to specifically prevent illicit conversions to R-134a, as well as the mixing of the two incompatible refrigerants. The EPA has done this by means of special left-hand threads on the refrigerant containers, matching threads on the end of the yellow hose, and uniquely sized service-port adapters on R-1234yf Manifold Gauge Sets and machines. Although more expensive, I would use only R-1234yf in an R-1234yf system, or nitrogen, for leak-testing purposes.

Good points, John