Good evening folks! So for a good while now my air conditioner has not been blowing cold at all. Almost lukewarm. Most folks say it needs a Freon recharge which is available at my local parts house. My concern is that if it needs recharged to blow cold again does that not mean that it is leaking out somewhere? I would like a step by step guide to recharging and testing for leaks if y’all would be so kind. Thanks! 

First off I typically hook up my manifold gauge and see what the static pressure is. If there is no pressure in the system then you need to start looking for leaks. Typically I would put a shot of UV dye in the system and recharge just enough to get the compressor to run. This will push the dye around the system and hopefully push it out the leak. Now using black light look over the entire system for the green dye. 

 

If the system has some pressure in it but not enough to start the compressor (<35 PSI) then I typically recharge and give a shot of UV dye. Then let the vehicle go for a day or two and then ask the person to return. I hope in a few days the green dye pushes out and show the point of the leak. 

 

Once the leak is repaired either typically bad o-rings or bad condenser. Then I typically test one more time by placing a vacuum on the system and seeing if it can hold the vacuum. My little 1/3 HP pump can typically pull 28inHg of vacuum. Wait for extended period. An hour would be optimal. Now check and see if you still have the exact amount of vacuum. If not them you've got another leak to go find. 

 

Now that we are sure there are no leaks then I would pull the vacuum. This ensures there is no moisture in the system. Now typically the system hold 3 can (rounding up). At that point I add the 3 can as a GAS (not a liquid). Never flip the can upside down where liquid can be discharged on the suction side this can hydro-lock the compressor and cause damage if not an explosion. I always charge A/C system on the lo side as a GAS. Now for typical Dodge Ram I would charge till there was at least 35 PSI on the lo side. Typically the high side can run about 225 to 275 PSI but this depends on the outside temperature and if the fan is partially locked or not.

 

After I've got the 35 PSI and the compressor is staying locked I will up the RPM's to about 1,500 to 1,800 and see if the compressor unlocks. If so I typically add a bit more freon to prevent cycling of the clutch which is bad. The compressor should not cycle when charged properly. If you already got the 3 cans in the system I stop. Overloading will actually degrade performance and make it run warmer on the discharge temp on the vents.

Edited August 29, 20186 yr by Mopar1973Man

The only thing I can add is if it is leaking in the hvac box, that is the only one you cant see.

Might see the green dye in the draining water.

So just buy the canned Freon from Napa? What do you recommend to pressure test as far as tool brand?

12oz cans only with just Freon. Do not buy the quickie cans they have stop leak and oil.

 

 

Does this look like a good kit to use? I’ll leave a link below. Found this in a YouTube video. https://www.amazon.com/XtremepowerUS-Vacuum-Refrigeration-Manifold-Detector/dp/B016APRO6Q

I dont a thing about the tools you linked. I bought a vacuum pump and gauges from Harbor frieght. The pump works fine but gauges are a little iffy at best. My son in law got my daughters Honda to hold vacuum with them. Then I used them on the Dodge and was having trouble holding vacuum. I did have a leaky compressor but during the work I also had a hard time getting the gauges to hold vacuum on there own. 

 

 I do have a question myself for all. Are the schrader valves in the test ports anything special? Just did the wife's Saturn over the weekend and one of hers has a small leak.

The same tools at Harbor Freight cost more and their quality is barely good for a do-it yourselfer.    https://www.harborfreight.com/automotive-motorcycle/refrigeration/3-cfm-two-stage-vacuum-pump-61176.html

 

 A mechanic starting out needs to buy quality tools that will last a long time and in tools you get what you pay for.   

I bought my setup from NAPA about 8 years ago. I'm going to need to replace my manifold gauges they are just physically beat up. Taken way too many drops, falls, and abuse over the years. My vacuum pump is still going today and does an excellent job. 

You can also rent these tools if you don’t want to buy them right now. 

I’m thinking I will wait till spring to repair the AC. I haven’t been using it much lately and fall/winter is coming quickly. 

Typically I won't do A/C recharging on cool or cold days. It throws off the entire pressures and volumes.

8 minutes ago, Mopar1973Man said:

Typically I won't do A/C recharging on cool or cold days. It throws off the entire pressures and volumes.

Thanks for that! 

Iv got a ton of stuff that needs to be done including tires and steering gear before I spend the money on AC equipment that I won’t need till next spring. 

(Cough) Quadzilla Adrenaline (cough)

18 minutes ago, Mopar1973Man said:

(Cough) Quadzilla Adrenaline (cough)

It’s on the list but Iv got more important things to direct my finances towards. 

Just gotta be that voice in your head...