Trying to put 134 a in a/c but don't know where to charge it

Your system may have leaked off the 134 refrigerant to the point that the pressure is too low to activate the switch that energizes the magnetic clutch on the compressor.
It could be other things,but check the charge first. don-ohio

suction side of compressor is low pressure port to charge Ra134 . required quantity can be checked by returned temp. or designed suction pressure

the hose fitting that you attach to the low side port will only fit that port-it cannot fit the high side (that port is too big) so you cannot do this wrong. The low (suction) side is between the compressor and the evaporator (passenger compartment, usually in the heater core plenium.)

Check to see that the cooling system is fully charged as there is a pressure switch that doesn't allow the compressor to function with low coolant pressure. You can get a can of R-134 A for around $10 at Wal-Mart with a pressure gauge on it. Remove the cap from the low pressure line and attach the can's line (follow can directions) Don't worry, line port sizes are different, so you can't mistakenly hook up to the wrong one. Gauge is self explanatory, don't overfill or you can ruin the seals, and good luck

You want to use the R-134. But you have to locate the low pressure port in order to charge it. I am not aware of its position exactly due to variations between models and years but if you follow the lines off of the compressor you should eventually run into a low pressure service port. However you do have the correct freon for the vehicle.

LOW PRESSURE PORT HAS A BLUE CAP ON IT.MAKE SURE YOU ARE USING REFRIGERANT R-134 BLUE CHARGE HOSE.R-12 CHARGING HOSE WILL NOT FIT R-134 SYSTEMS.SEE YOUR CAR HAS R-134 REFRIGERANT SYSTEM. THE EARLY 90S CARS HAVE R-12 REFRIGERANT SYSTEM.YOU NEED R-134 CHARGE HOSE SET.

LOOK FOR A BLACK CAP OR BLUE CAP LOW PRESSURE CHARGE PORT WILL BE ON SAME LINE NEXT TO DRIER OR ACCUMULATOR.OR TO EVAPORATOR LINE.DONT CHARGE PORT WITH RED CAP.THATS THE HIGH PRESSURE PORT AND DISCHARGE PORT.WEAR SAFETY GLASSES WHEN HANDLING REFRIGERANT.VERY DEADLY IF YOU INHALE. R -134 TRY NOT TO BREATHE AROUND IT WORK WHERE THERE IS GOOD FRESH AIR FLOW.

if you truck has r-12 you need to convert to r-134
if you truck has been converted to r-134 the small port on the low pressure side is the port to use..
the truck must be in a warm aera about 80 degrees
then hook up the hose or gauges on to low side
start the truck and turn the air on (putting it on high cool and high blower open the can of freon and as the compressure in the truck starts to draw the gas in rock the can from side to side .. if the gas is going in the can will get cold

If it is a quick connect fitting, it is R-134a
The low(charge) side fitting is: 13mm
The high side fitting is: 16mm

If it is a threaded fitting with threads on the outside, then it is the older R-12 refrigerant and can only be serviced by a licensed air conditioning service.

The low(charge) side is 7/16" threads
The high side is 3/8" threads

When servicing your air conditioner it is best if you have gauges, but it can be done without, just be careful.

Assuming the air works, but just not putting out that much cool air, then 1 or 2 cans of refrigerant won't hurt.

If there is no pressure/refrigerant in the system at all then it is usually a sign of a leak and should be taken to a pro because you may need to replace the receiver/dryer and have the leak fixed. The system needs to be evacuated for maximum efficiency if there was a leak or if hte system has been opened.

Adding too much refrigerant can be catastrophic as the high side pressures can reach 200-300psi on a hot day. So if you happen to have a low side gauge, and it reads somewhere between 35-45 with the Ac operating, you are golden.(tire gauge won't work)

Don't be surprised if the compressor doesn't kick on right away. Some vehicles are equipped with a pressure switch to keep from damaging the compressor if it runs low. Usually after adding one can, it is enough to engage the compressor.

Hope this helps.

Mark

Heater Control Module