Should I add more refrigerant to my AC system?

I recharged the AC with pure R134A (DuPont Chemours brand)

1. Ambient temp 70°F
2. After purging the air and hooking up the manifold gauges without turning on the truck, the low and hi side were at 70psi.
3. After turning on the truck and AC and letting it run for 10 minutes, the low side was 15psi and high side was 100 psi.
4. I only bought one 12oz can of R134A. The system took all of it and the low side was 28psi and hi side was 150psi. I was shooting for 35psi low side and 155psi high side based on the PT chart so should buy another can and add a little more?
5. Temperature was 42-44°F at the vents at idle, depending if the compressor cycles on or off.
6. The compressor cycles on for 12 seconds and the cycles off for 12 seconds. Is this normal or should the compressor stay running on longer?
7. Even though I bought pure R134A, it left neon green residue on the hose fittings after disconnecting everything. Is this UV leak detection dye or compressor oil?

 

You will loose a little dye when disconnecting- just make sure you valve stems are not leaking. As per temp maybe bump low to 35 PSI

 

The 4.0 V6 version holds 22oz of R-134a.

 

First of all, stay away from suicide cans!!!!!!!
Second, go get a proper evac and recharge done by a professional if you are just guessing at amounts and pressures.
Sounds like it is severely undercharged. On a 90-100 degree day you should be at 35-45 psi on the low and 275-300psi on the high side.
Make sure your fan is pulling air over the condenser and radiator. Make sure your cooling system is at peak performance. Make sure you have no ambient air in the ac system. Pull a deep vacuum after the system is properly evacuated. If the system was exposed to enough ambient air the desiccant bag will absorb moisture and will have to be replaced. This means replacing the condenser on our trucks.

 

OP this ^^^^^ is great advise. Your original post did not mention why you were recharging your system. You need to seek the help of a professional to get your A/C system repaired properly.

 

I recharged it because the AC was no longer cold anymore. I've owned it for 13 years and this was the first time I had to recharge it. My plan was to recharge it and see how long it can last before taking the next course of action.

 

Just so you know, I’ve seen those suicide cans cause way more problems than they solve. Even if they are used as temporary fixes

 

I thought using those refill cans that come with a cheap looking low pressure gauge, leak sealer and other additives were considered suicide cans?

I used a can of pure R134A and recharged it through a manifold gauge set while monitoring the low and high side pressures.

 

Does anyone with an older 2nd gen like 2005-2008 never had to recharge their AC and it still blows cold air like new?

 

Pressures can be manipulated by many outside issues. I can give you a bunch of examples I had when my pressures were good but the system was extremely undercharged.

 

After owning the truck for 13 years, i'd say its due for a real AC system maintenance. You'll definitely need a proper evac and recharge. It can then be accurately filled by lb.

 

This past summer I did some AC maintenance on my 10 year old (2009 model year but bought in Sept 2008) 2nd gen DCSB SR5 4x4. I'm a SoCal truck living in the I.E., so basically desert where I run the A/C 11 months out of the year. The truck took a full can of R134a to bring it back up to recommended pressures. I used a proper A/C manifold gauge, and had an experience mechanic friend help me out on it. It was still blowing cold, just taking longer to get to cold, and now it feels like new again. I understand microleaks happen since no system is perfectly 100% "sealed." It's good to check on your A/C and do some system maintenance.

 

Looks to me like you did it right. Is it cooling better?
Suicide cans are from the olden days of R12. Anyone could buy a kit, 12" hose and a can of R12. The service ports were all 1/4" flare. Hook thing up to the wrong (high) side, and BOOM. The can blows up in your face. After that check valves were installed in the hose.
Now days, adding cans of who knows what in your truck helps the AC commit suicide.

 

I notice that the small cans still have the cresent-shaped score in their bases to control a burst. So I will still call them suicide cans.

 

Those cans should only be used if you don’t care about your vehicle and just need a temporary fix for cooling. Like if you’re planing on selling st the end of summer and just need a/c for a few months. They really f up your a/c system.

 

Is being a little undercharged ok as long as it's cooling?

 

A proper charge is for maximum efficiency. You're not getting the most out of your A/C system as well as your compressor has to work extra hard to return your gas phase refrigerant to its liquid phase to use utilized again.

The R-134a refrigerant used in car air conditioners would normally be a gas (it boils at a frigid 15 degrees below zero). If you compress it and pressurize it enough, though, it turns into a liquid. The compressor in your vehicle’s A/C does exactly that, so you have liquid R-134a pumping through part of the A/C system. When that liquid reaches the in-dash cooling unit (called an evaporator coil), it passes through a valve that lowers the pressure. The lower pressure allows the liquid to boil and evaporate back into a gas. It absorbs heat from the air in order to boil. With the heat removed, the air becomes cold. If you don’t have enough refrigerant, it won’t be able to cool the air.

 

Yes a lot better. It hasn't been that hot here lately so I can't put it through a real test. Yesterday it was like 75°F outside and the temperature at vent was 42°F with the fan speed at the lowest setting. My concern is that the compressor still cycles on and off every 12 seconds. Sounds like it's still a little low on refrigerant?

With my 2018 4runner, the temperature at the vent is 38°F after checking it today to get a comparison to my Tacoma.

 

75f, so no load on the AC. Cycling at that temp is normal, especially if the fan speed is on low. Check vent temps on high. Don't be concerned because a different vehicle has a different vent temp. Nothing is ever exactly the same in the AC world.

 

The first thing I would do before taking the AC system apart is to verify that the system is properly sealed.

Evacuate all remaining R143a using a proper evacuator system.

Vacuum the system as low as it will go and shut the vacuum pump off.

Ensure system holds vacuum. If it does not hold vacuum, you have a leak and require further diagnosis and repair. If vacuum pressure stays consistent, recharge system accordingly.

Low/Hi pressures are a good go-by but poor unit of measurement because of so many variables, especially if you do not diagnose ac systems regularly. Typically adhering to manufacturer R134a quantity in oz is more precise.