A/C pressure fluctuation, semi-cool air only

[engineco16]

In January I had $1500 of work done on my 1996 3.0 ranger to pass the smog test. A few months later when it got warm I went to run the a/c and it was blowing out the defrost vent. Took it to a shop and they found a wire Ford had not connected. OK, so now it blows out the right vents, that's when I noticed it wasn't blowing very cold.

Jump to now. I figure it needs an a/c recharge since it's blowing cool and I can hear the compressor cycling. So I buy the recharge kit, hook it up and note the follolwing.

When the compressor engages the pressure drops to 18-20, when it cycles off it goes up to 48. It was probably close to 90 outsaide and it's been 11 years since the system was recharged. The compressor is cycling on and off at 5 second or intervals, so the pressure is bouncning up and down.

So I was guessing it doesn't need recharging. Well that was before I started reading some threads on this forum. So can someone confirm I just need to recharge the system?

Thanks,
Dave

 

[scucci]

when the compressor kicks on, the low charge allows the low side to drop from the static pressure to the low cut off pressure. At 25 psi the low pressure switch cuts power to the clutch. Then the low pressure starts to rise untill it hits the 40 to 45 psi turn on point, powering the clutch and causing the pressure to drop. You are low on refrigerant. On a hot day the low side should hover around 30 psi and rarely cycle.

 

[engineco16]

Thanks. After reading some more I kind of figured that out.

I went out, hooked up the can, checked the pressures again then proceeded to fill the system. Once I started charging it stopped cycling. I dumped the whole can in and it now blows ice cold and the pressure was at 27-28.

Thanks,
Dave