Specific procedures for charging/evaluation - How? Where? What?

Information on some common auto air conditioning topics.
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Specific procedures for charging/evaluation - How? Where? What?

Post by TheBTR »

I searched the forums, but didn't find what I'm looking for. Can someone reply with the following information? Thanks for your help.

When charging (using a charging chart, not by refrigerant weight) a single evaporator R-134a system that has 2 blowers (one for the front seats, one for the back seats --- e.g., 2000 Ford Explorer) and/or evaluating the system's performance (by gathering temperature and pressure readings), what is the CORRECT procedure for each of the following:

1. Vehicle should be parked in the shade - yes or no?
2. All doors and windows should be open, or closed - which one?
3. A/C should be on recirculate - yes or no?
4. Both blowers (front and rear; single evaporator system) should be on - yes or no?
5. Blowers should be on high, or medium - which one?
6. Engine should be at idle, or at 1500 RPM - which one?
7. Ambient temperature should be measured at the blower return in the passenger-side foot well, or anywhere outside of the vehicle, or directly in front of the condenser - which one?
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Re: Specific procedures for charging/evaluation - How? Where? What?

Post by philipswanson »

Did you post this yet. Many would like to see it I'm sure.
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Re: Specific procedures for charging/evaluation - How? Where? What?

Post by Tim »

In the tips forum.

vacuate and Charging Procedure.

Attach a/c manifold gauges to the vehicle. Make sure you attach the correct hose to the proper service port. This is very important to prevent personal injury! Attach center (Yellow Hose) to a UL approved a/c vacuum pump. Open both of the dials on you’re a/c manifold gauge set. This will allow the system to be evacuated through both the low and high side of the system. Turn your approved vacuum pump on starting the evacuation process. 30 minutes usually will be enough time. If the vacuum pump has ballast read the owner's manual concerning this option.

When the system has achieved a state of 29.9 hg’s of vacuum close both dials on the a/c gauge set. You may lose up to 1 hg for every 1000 feet above sea level depending on the capacity and quality of the pump. At this point wait for 5 to 10 minutes letting the vacuum boil off any moisture trapped in the refrigerant oil. This is also a good time to watch and see if the vacuum has returned to a zero state. If so you need to check for leaks in the system. Assuming the system is holding a vacuum after letting the moisture boil-off repeat the evacuation procedure again. This process may need to be done a few times before all moisture has been removed and you see no degradation in a vacuum after closing both dials for 5 to 10 minutes.

With both dials closed remove the center charging hose attached to the vacuum pump and connect it to either a can tap and refrigerant or 30lbs refrigerant cylinder. Open the valve on either the can tap or 30lbs cylinder allowing refrigerant into the charging hose. With refrigerant in the charging hose slowly crack this hose at the manifold gauge bleeding off any air that may have gotten trapped when moving from the vacuum pump to the refrigerant source. Only the slightest amount of refrigerant should be released in this process so be sure to tighten the charging line quickly!

Open only the low side dial on you’re a/c gauges allowing refrigerant to flow into the system. Again I stress the high side must be closed or you may cause personal injury to yourself or others! Start the vehicle and turn on the a/c system with the blower on the highest speed. In some cases, if the compressor clutch has not engaged you may need to bypass the low pressure cut out/cycling switch. Refrigerant should be charged as a gas but in some cases, it may be necessary to charge as a liquid. Be careful not to slug the compressor with liquid refrigerant! Charge system to OEM amounts and pressures if you are using the refrigerant the system was designed for. If the vehicle is has been or is being converted start with about 60 percent of the original charging amount. After getting 60 percent of the original charge slowly add an ounce at a time until you reach the best possible vent temperature and pressure readings. If you do not know what your systems operating pressures are you can use the 2.2 x the ambient temperature as a guide. This should only be used as a guide as many systems will need more or less refrigerant to achieve proper cooling.

Having a weak fan clutch or an inoperative electric fan will cause system pressures to be incorrect. So make sure these components are working correctly before charging a system!

In lower ambient climates, doors and or windows of the vehicle may be required to be open to achieve proper cooling when charging the a/c system.
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Re: Specific procedures for charging/evaluation - How? Where? What?

Post by swampy 6x6 »

1/ charge/repair in shade ,but remember vehicle will operate in full sun
2/ a good air con should be able to operate with at least 1xdoor open if not all !!!
3/ yes always test a/con on recirculate
4/ & 5/ both blowers on medium speed
6 / pressures and temperature performance need checking at idle and fast idle 1500rpm
7/ ambient should be measured in the shade in almost no airflow

Vehicle done 60,000miles or 100,000km = clean evaporator core
Change txv if under dashboard and evap is being removed for cleaning

Squash heater hose to block water flow ,this will test blend doors or heater tap . If heater is working it will elevate vent temps .
ensure condenser fan is working and its effect on condenser pressures
check for ducting from condenser to radiator
security of fittings /belts / hoses etc
check for oil stains
evap drain working
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