I have a car AC question and hoping you guys can help
 

Hey all! My ‘06 Nissan Titan 4X4 doesn’t blow cold AC anymore so I bought a can of r134a so I can fill it up myself. I was expecting a near empty charge but when I hooked the can/gauge to the L port, it would fluctuate from 0 to the green section then back down to 0. I’d hear the AC kick on and off even though inside the cabin, I have the AC on full blast the whole time. Is it normal for the AC to fluctuate like that? What could be causing the fluctuation if that’s not normal? Thanks!

Similar issue with my 03 Avalanche.

Changed the pressure switch (no need to pull a vacuum for that at least on my car) and still showed same 0-green as you. I kept the can attached and it took in approx 1/2 can and starting cooling nicely.

Regretfully I used the can with sealant and I think that it now clogged the orifice tube. No cold air anymore.

Is it cycling the compressor in very short cycles (2-10 secs)?

To just add refrigerant is the typical first step of the throw parts at it crowd. Sometimes that is the right thing to do. But not always. There are lots of other parts, and it is a system, not just a compressor and vents.

If the compressor is cycling on an off that can be a sign the pressures are low. Or high!

As said above. Likely it's low from your description, so adding a small amount was enough to overcome the low pressure switch. But it's still low as the compressor continues to cycle. You could add more........

Get a set of gauges on it so you KNOW what is going on . I find guessing is not an accurate form of diagnostics .

As said, need to know what the high side is. If it's not on and pressure in the system is 100 +/- psi (equalized) depending on ambient, I'd be inclined to point at the expansion valve being stuck and the compressor is pulling the low into a vacuum.

Hook it up to a set of gauges and let us know.

Gauges are mandatory, then jump the low pressure switch to get the system to accept the charge.

there is a reason you need to add 134. it has a leak. period.

yes, comp will cycle when charge is low.
it will or may also cycle when charged and fan is on low/ low heat load on evap. (when engine is above idle).

all good advice. If it starts to blow colder with the can charge, then you might add more. Always charge from the low side, not high side.

The responsible advice would be to get a set of gauges. While you're there, buy a set of green viton o-rings in various sizes, and the 134 without the seal conditioner or dye. If it turns out that the compressor is done, then I would say flush, change compressor and receiver dryer. You should pull vacuum also, at least 45 mins or so.

I just picked up a set of gauges from HF and a new vacuum pump (for the AC;) )
The gauges were about $60 and work great. Worth every penny.

So after pulling vacuum, watch the needle to make sure you don't have a leak before charging the first can. It'll go quickly.

Whatever leak you have is very small if your compressor still cycles. If it took a couple of years to bleed down this low then you will not find the leak unless you are a most awesome AC geek on par with our dear banned friend, WWest.

Anyhoo, get the gauges and even buy the super cheap vacuum pump from the freight if you don't want to spring for an electric vacuum pump. But if you do want to, buy their better pump.

You need to get it vacuumed out to then put the right amount of R134 in.

You can put the refrigerant in without pulling a vacuum but its nice to know you are at a zero starting point as to refrigerant weight.

R134 with no BS additives is less than $9 per can at Walmart. Find that sticker under your hood and find how much your car's capacity is. Convert to ounces. A postage scale helps if you need to only use a partial can.

The best stop leak I have found is called Red Angel. Just an FYI.

You need an injector
https://www.amazon.com/dp/B00IPS3G96/ref=syn_sd_onsite_desktop_166?psc=1&spLa=ZW5jcnlwd GVkUXVhbGlmaWVyPUFSRUlPUk9BTlFZRzkmZW5jcnlwdGVkSWQ 9QTA3MjAxNzAxVlVCUVk5SUFGSjFDJmVuY3J5cHRlZEFkSWQ9Q TA2MzUzNzgyNURVSFZKRVBWRTU2JndpZGdldE5hbWU9c2Rfb25 zaXRlX2Rlc2t0b3AmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob 3RMb2dDbGljaz10cnVl

And then the stop leak
https://www.amazon.com/Red-Angel-Stop-Leak-Ounce/dp/B00NSRVP6A/ref=asc_df_B00NSRVP6A/?tag=hyprod-20&linkCode=df0&hvadid=312181776237&hvpos=&hvnetw= g&hvrand=10246014161489030671&hvpone=&hvptwo=&hvqm t=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9015531&hv targid=pla-569760800311&psc=1

The better part of putting it into a vacuum rather than just topping off with Freon is there is then no air in the system. That being said, many times I have gotten cold air by just topping off. Buying a set of gauges and a tap probably cheaper than paying someone to do it these days.

Thanks all!