Figure 1. Show a TXV with its sensing bulb looking like a coil spring.Continued from previous discussion; the Hi side pressure reading is 250 psig. and the low side pressure read 50 psig. And the evaporator temperature is about 30 degree C. That is no cooling at all. the evaporator temperature should be at least 12 degree C.
Now with these readings, the defect could be:
1). Defective compressors
2). Defective TXV.
It definitely is not undercharge, normal operating pressure in hi side is 230 -250 psig, low side pressure 30- 40 psig. at outside temperature of about 30 degree centigrade.
The first thing to do, is to check the TXV, is it providing enough restriction or was it stuck open? Seems the best solution is to replace the TXV, evacuate the system ,replace TXV, charge up the system and check the gauge for proper operating pressure.The last thing we want to do, is to suspect the compressors is defective.
The last time I service a unit is even if I rev up the engine, the compressors low side just wont go down the 40 psi mark even with proper charge, found out that one of the swash plate crack, and the whole compressors had to be replaced. it is a ZEXEL 160cc compressors for a Nissan vannete van. Before I replaced the compressors , I make sure the TXV valve is not the culprit. A stuck open valve can also create this conditions.
Figure 2. Show the adjustment spring using a HEX tool. this is the discharge side connected to the evaporator.
Figure 3. Show the inlet side of the TXV. connected to the filter drier.
Now about recycling the TXV. first you should have the proper nut and fittings to connect the TXV to an air pump. look at figure 4.
Figure 4.
What we are after is the low side reading. Now waht I have done is, with the proper pressure applied to the inlet of the txv ie. >70 psig. Read the scale on the lo side gauge, if its the same as the hi side gauge, good, the Txv is not stuck. now apply an ice to the feeler bulb. the pressure in the low side gauge should drop to at least 20 psig. if not, try adjusting the hex nut of the txv, naturally you have to undo the firttings to reach the hex nut screw. It a trial and error situation, but eventually if you get the feel of it, it easy. by the way the 20psig is for r-134a gas.
Just make sure if the ice is remove from the feeler bulb, and warm up the bulb with your hand, the lo side pressure should immediately increase to the hi side pressure reading. if not replace the TXV.
