How To Recharge Ac System?

[zdanman 0]

Thanks for your replies.

 

The outside/inside air blend door is 98% shut (I can only push it 1/16" farther) so I don't believe thats the issue.

As said before I cant push the heat/cold blend door much further either.

 

Now I'm thinking the new orifice tube I got from Autozone is junk.

 

In the morning, (outside temp is 70 F) the gauges and accumulator look like this...

 

 

 

Which is great for the inside because the air passed the evap is 34 F (air out the vents is 40F) !!!  However obviously the lines have 25 F freon flowing through them (according to the gauges) and as you can see are freezing.  I thought the orifice tube was supposed to stop that from happening and/or the accumulator switch is supposed to shut the compressor off if the pressure gets below 32 psi (aka 32 F - freezing).

 

Either way when, in the afternoon when its 88 F outside the evap air temp (as stated before) goes up to 40 F - vent temp goes up to 50 F - and low side pressure goes up to 35 psi (35 F freon).  Something obviously is not doing its job - either letting to much freon go through in the morning and not enough in the afternoon... what component regulates this?

[djdevon3 828]

Sounds like you really want to read the 2001 Work Shop Manual section 07 on the HVAC system.

[snailman153624 167]

Your pressure looks low.  It should be a little over 200 PSI on the high side IIRC.  I would suggest topping up the refrigerant a little more.  The factory fill spec is for factory equipment; you probably bought an aftermarket receiver/drier, and the system capacity may be a little different.

 

The pressures will vary with temperature, this is normal.  The line freezing is a classic symptom of too low refrigerant.

[chief tool 44]

^ what he said.

 

I normally work with 220 high / 40 low. for a warmish day, but yes the pressures will vary with temp. Sweating suction lines normally indicate low refrigerant - freezing *usually* indicates alot low.

Read the below document. Its a good manual. All in metric tho so you'll need your conversion tabels.

 

http://www.ariazone.com/manuals/Automotive%20Air%20Conditioning%20Training%20Manual.pdf

[zdanman 0]

Now my mazda is doing the same thing as what my dodge is doing.... pressure is going back and forth all over the place.

 

I have both vehicles vacuumed and charged to the factory amount.

 

I didnt loose any vacuum overnight so I assume there is no leak issues.

 

I also tried adding an extra 100 grams later on and it still does the same thing.

 

 

I charged it the same way this guy does it....

 

[zdanman 0]

.... annnnnnnnddd .... nobody knows.

[gold_1999_626 0]

zdanman, the reason the pressures are doing that is because the compressor is cycling.  It's cycling because the suction side is pulling below the threshold of the low pressure cutout switch.  That system appears to be low on refrigerant.  (It doesn't use Freon, which is the DuPont trade name for R12!)  Without knowing the conditions under which the readings were taken, it's impossible to say how low it is.  There are many factors that affect what the pressures are, including the type of metering device, which in the case of the Mazda is an orifice tube, ambient temperature, amount of airflow passing over the condensor and evaporator, dew point (read humidity).

 

As an ac man, I have "fixed" so many systems by evacuating refrigerant because people just keep adding and it never gets better.  Fortunately, most systems also have a high pressure cutoff switch to keep the pressures from becoming extremely dangerous.