AC Compressor not kicking on when trying to recharge system

[JohnHere]

Thought I'd mention that Tim at AC Kits, this site's sponsor, has two styles of side can taps in stock. One can handle three types of cans: R-134a, R-12, and oil. The other one handles only R-134a cans. Each is priced the same.

I don't recall your mentioning the vehicle's make model, and year. But if it holds 24 ounces, that would equate to about two cans of pure R-134a charged into an original R-134a vehicle. A better way is to weigh-in a precise charge. Newer vehicles hold relatively little refrigerant and are very charge-sensitive. System performance can be affected if the charge amount is off by even an ounce or two. Something to keep in mind.

Regardless, it does seem as though your compressor is weak if you have a full charge in it now based on the pressures you reported. At 75 degrees ambient, engine at 1,800 RPM, doors open, and blower on high, I would expect to see the high side at around 190 PSI. Conversely, the low side seems high, so I'm not surprised that you're seeing vent temps in the uncomfortable 50-plus degree range--not acceptable for Phoenix or for the humid South, where I am.

A couple of additional questions: When you changed the TXV, did you find any type of debris or desiccant beads clogging it? Also, did you replace the receiver/dryer at the same time?

[cmilot6329]

Hey sorry, forgot to include my vehicle. It is a 1999 Nissan Maxima. Calls for 1.43 +/-.11 lbs of r134a refrigerant so figured 2 cans would be about right. I actually went to walmart looking for the $4.88 cans as I used to always get those but they had the self-sealing taps. I found some without the self-sealing at autozone for $7.99 of pure r134a.

Didn't see any debris or desiccant beads in the old TXV. I did not replace the receiver/dryer but if I end up replacing the compressor I will definitely swap that out as well.

I'll look into getting one of those side taps through the sponsor.

Going to drive to work today in a few hours so we'll see how it performs in the day time.

[JohnHere]

It might say 12 ounces on the can, but it's anyone's guess as to what a can actually contains without weighing-in each one. I've seen some of those "12-ounce" cans yield only nine or ten ounces of refrigerant according to my equipment. It's possible that the system could be undercharged by as much as six ounces or around 25 percent--a significant shortfall that will affect pressures and performance.

Before you spend the money for a new compressor, I'd recover the charge (or have it done) to determine what's actually in there now. I wouldn't be surprised if it's low. Then, recharge it to the correct amount by weight and revisit your pressures and vent temps.

My reference material for your vehicle specifies 23.0 ounces of R-134a and 6.80 ounces of PAG-46. Sounds like you're looking at the under-hood sticker, which always takes precedence. According to your figures, minimum charge would be 22.9 ounces and maximum would be 24.6.

[cmilot6329]

Thank you for the reply. I bought several extra cans so i'll weigh them and then weigh the empty can to see what amount is in these. Yes I got those numbers from the sticker on the bottom of the hood.

So an update on the drive to work today. Temp at center vent stayed at 47-48 and did not fluctuate at all like it did before between 60-80. If I remember correctly last time I replaced the compressor in this vehicle the lowest I could get it was about the same so it may be working normally again. I can live with these temps as it feels very cold to me. Will let you all know if anything changes.

Thanks again!

[Cusser]

With today's Phx temperatures, I would hope for lower, but maybe that's what a Nissan Maxima can deliver. Of course it's only about 85F here today outside, so will get 30F higher in summer. My 1998 and 2004 Nissan Frontiers have great AC, and those have their condenser/radiator cooled by a fan clutch/belt-driven fan.

Are all your electric fans in the engine compartment running when the AC is switched on?

[cmilot6329]

Yes all fans are running with A/C on.

[Tim]

With today's Phx temperatures, I would hope for lower, but maybe that's what a Nissan Maxima can deliver.

I may be crazy. I got up at 3:00 am and turned the furnace on.