Automotive Air Conditioning Information Forum

Hi im in the process of topping off my ac refrigerant on my 2013 mustang gt which never had ac serviced. My ac is still cool but not cold and compressor would cycle on and off often. I decided to do this myself and watched quite a few youtube videos and got myself a yellow jacket 42006 series manifold to get it done right.

Well this is what happened, after everything was hooked up i loosen low pressure knob slightly to recharge refrigerant and low pressure gauges was climbing but then it would also drop down. After the whole refrigerant can is empty my low pressure side is still reading 27psi while my high pressure side now is at 350psi. Before i started my low was around the same 27-30psi while high pressure side was only around 180-200psi. I stopped immediately, unplugged everything thats when i noticed my low pressure cord inner rubber sleeve end at the coupler adapter was ripped and teared. Im not sure if thats the cause but my can was not leaking and can was empty after recharge so why did my low pressure side not move while my high pressure side increased up to 350psi?

You need to reclaim the refrigerant that is in there, vacuum down, and recharge to the correct charge, and we can go from there

but my problem is i emptied almost 2 can my low pressure gauge didnt change only high pressure gauge got increased from 200 to 350psi.

How were you testing the system with your Manifold Gauge Set hooked up--engine at 1,800 RPM, windows open, compressor running, blower on high? If so, the pressures measured by your MGS before you added any refrigerant look pretty good (ambient temperature not mentioned). With a high-side of 350 PSI after adding one full can of refrigerant, and not knowing how much the system contained to begin with, it sounds like the system is now overcharged.

tbirdtbird has offered some solid advice. Start off as he suggests so at least we know that it has the correct charge in it. Then we can diagnose from there. It might not have been the refrigerant charge at all.

The specs I have for your car call for 21 ounces net weight of R-134a and 4 fluid ounces of PAG-46 oil.

I forgot to mention not to charge with refrigerant containing sealers or other additives. Pure refrigerant only.

JohnHere wrote: ↑Thu Apr 14, 2022 8:16 pm How were you testing the system with your Manifold Gauge Set hooked up--engine at 1,800 RPM, windows open, compressor running, blower on high? If so, the pressures measured by your MGS before you added any refrigerant look pretty good (ambient temperature not mentioned). With a high-side of 350 PSI after adding two cans of refrigerant, and not knowing how much the system contained to begin with, it sounds like the system is now overcharged.

tbirdtbird has offered some solid advice. Start off as he suggests so at least we know that it has the correct charge in it. Then we can diagnose from there. It might not have been the refrigerant charge at all.

The specs I have for your car call for 21 ounces net weight of R-134a and 4 fluid ounces of PAG-46 oil.

The way i tested was had the yellow jacket manifold hooked up and couplers at pressure port opened, engine on ac on max, windows are closed, compressor running but no revving. Ambient temperature outside today was around 80f, my initial readings before recharge was low pressure around 25-28 psi and high pressure around 180-200psi. From charts i see online it seems with the ambient temperature i had, my low pressure should be around 40 psi. So i slowly opened the low pressure side to fill refrigerant but gauges slowly moves up but as soon as i close the manifold the psi goes back down to 27 psi, why is that?

Thanks everyone for helping, im just trying understand what is going on and why it is behaving this way. Im not sure if its the faulty manifold since i found low pressure cord end inner rubber sleeve ripped and teared, that might cause inaccurate reading? but high pressure reading seems high. I might get a new manifold to retest my readings. Also will it be okay to drive with ac off, will it damage the ac system if the system is overcharged or have issues somewhere?

edit add on
yes i only bought pure refrigerant non of that sealer additives.

You are repeating yourself.
Your original pressure readings were within the range of normal. Why did you add more freon?
Now your high side is too high, suggesting as John says overcharged, or contaminated with air.
Pressures should be read with engine at 1800 RPM for all cars. Max cool, max fan, windows open.
As John states the original problem may not have anything to do with the amount of freon. There are other components which can give trouble, such as filter driers, expansion valves, orifice tubes, cabin air filter, etc.
There is little that can be done if we do not know for a fact that the correct charge is in there, thus our advice. Once the correct charge is in, then we can diagnose from there. If one of your rubber seals in the hose is torn, you must replace if before proceeding.
You do not need the temperature charts to figure out the problem, they will only confuse you.

Has anyone ever serviced the system at all, ever? Add refrigerant? If sealer was put in at anytime by anyone, all bets are off.
Not all Youtubes are accurate, BTW.
In your first post you implied that you added 1 can of freon. Later on you now tell us that you added 2 cans. Truth be told we have no idea if the system has the correct charge, and today's systems must have as close to the correct charge as possible to work.

tbirdtbird wrote: ↑Thu Apr 14, 2022 8:51 pm You are repeating yourself.
Your original pressure readings were within the range of normal. Why did you add more freon?
Now your high side is too high, suggesting as John says overcharged, or contaminated with air.
Pressures should be read with engine at 1800 RPM for all cars. Max cool, max fan, windows open.
As John states the original problem may not have anything to do with the amount of freon.
No symptoms were given about the system before you added freon.
There is little that can be done if we do not know for a fact that the correct charge is in there, thus our advice. Once the correct charge is in, then we can diagnose from there. If one of your rubber seals in the hose is torn, you must replace if before proceeding.
You do not need the temperature charts to figure out the problem, they will only confuse you.

Im repeating myself because my weird issues are not really explained. My first post of the problem has already stated the reason why i needed to recharge my ac. As for suggestion for emptying the system and recharge to correct level, how can i do that when im already having trouble adding refrigerant. The temperature and psi chart guide gives you an estimate where your low and high should be at.

Ignore the charts. They only serve to confuse IMHO.

For instance, at 40 PSI, the evaporator would be around 45 degrees, resulting in center-vent air of more than 50 degrees--hardly enough cooling to provide a comfortable cabin. At 27 PSI, which is what you measured initially, the evaporator would be just above freezing, and it would provide conditioned air of around 40 degrees at the center vent--exactly what you want. That led me to suggest the problem might lie elsewhere and not with the amount of refrigerant in the system.

Measuring 27 PSI on the low side indicates the system is operating correctly and that the Thermostatic Expansion Valve (TXV) is doing its job.

Also note that you can't charge a system by pressures alone. The refrigerant must be weighed-in using a highly accurate refrigerant scale or an RRR machine (Recover Recycle Recharge) that the professional shops use. So a pro shop can recover what's in there now, evacuate the system of all air and moisture, and recharge it precisely to specs. Having that done first would be money well spent, I think.

It sounds like you have a bad o-ring on the low-side coupling. Replacements are readily available, so there's really no need to try another Manifold Gauge Set. What you already have is a high-quality set.

Very glad to learn that you used pure refrigerant.

Yes, you can drive the car with the A/C system turned off.