Aoa Fellow pakwheelers
I own a khyber 96, it had ND a/c system using r-12 originally which was later altered with a Sanden compressor (SD-505) with r-12 in 2005.
SD-505 is Sanden wobble plate piston compressor. it has 5 pistons and total displacement capacity of 5 Cubic Inches (approx 82cc) nearly same as that of ND compressor.
The OEM serpentine condenser was not compatible with SD-505 and was causing head pressure to rise above 290psig at 40C(104F) ambient temperature so had to keep the refrigerant charge below normal to accommodate the issue.
So recently I replaced the condenser with a larger one. Its a universal type serpentine condenser with dimensions measure 584x304x32mm whereas the oem was 482x304x20mm.
Still using the original ND condenser fan. It is not good but better than the after market sanden fans. I have plans to change it with a better one from bilal gunj.
As the summers arrived the cooling reduced significantly, I decided to diagnose it by myself.
The system was running low on refrigerant as evident from the manifold guage set which i bought from brandreth road in rs 1400/-. The low and high side readings were 18psig and 150psig at 32C ambient temperature.
I did some research how to recharge r12 in car's a/c system and then bought a can of R-12 (forane-12) for rs 250/- It was chinese but did a good job afterwards.
With AC temperature pressure chart for R-12 in front of me, i noted the ambient temperature which was 39C (102.2F). At this temperature the static temperature of the system should be around 121psig.
I connected the red hose of the gauge set with the high side (near drier) and the blue hose to the low side ports. With A/C off, both gauges showed the same reading (static pressure) which was 102psig (low!).
Started the engine and A/C. Kept it running for 5 minutes to stabilize the system.
Placed a pedestal fan in front of the condenser, front door/window closed, blower at max and rear windows open.
Connected the r-12 can with the middle port of the gauge set. Slightly opened the tap on top of the can and slowly loosened the pipe from the gauge set to let some r12 escape to avoid air from entering the system and tightened it immediately.
At 39C (102.2F) ambient temperature and engine at 1500rpms, I was looking for low/high side readings of 30/240psig.
It took around 10 minutes to achieve the desired values and at that moment the temperature of the air from the evaporator blower was noted at 1C (34F). thermostat was bypassed for testing.
I shared my experience with you to get to learn more from you and in some cases may be I can help some one in making a diagnosis.
I am not at all good with pictorial uploads but if someone insist I will surely do it.