Doug Lassiter

2003 Civic LX, with 140K miles. AC has been working only slightly. Never refilled. Vent temps are only about 10F lower than outside ambient temp. So I figured I'd top it up with R134a. (I've done this before on other cars.)

Ambient temp is 100F (yeah, ick) and so I'm targeting 50-55 on the low side. Car on and warmed up, a/c system cranked up. Pressure on the low port is 45 at start. I open the can of refrigerant, and it quickly rises to 55 or higher and stays there. Gee, that just took a few seconds! I bleed to get back to 55. But there is little change in the performance of the system. Maybe now only 15F cooling. What gives? Other cars I've done this to, the temps drop dramatically after top up. I'm expecting a 40F cooling.

I was a little surprised that the pressure was so high to start out with. On the other cars I did this with, the starting pressure was a lot lower.

So what gives?

Doug Lassiter

I'm wondering if most of the pressure in the system is not, in fact, refrigerant. Not sure how that could happen. But I guess I could bleed it all off an refill.

ezone

Need to know both low side pressure AND high side pressure, both at idle and 2000 RPM

Maybe it did not need any freon at all. Maybe it had a different problem.

Doug Lassiter

So can I measure the high side pressure with my 100 psi gauge? Yes, it appears it didn't need any refrigerant at all. Would appreciate some specific advice about where to go from here.

ezone

No, you'd need a real AC gauge set as the high side can run up to 350 or so....and as high as 500+ if things go drastically wrong.

Doug Lassiter

What would cause the high side pressure to be low? That the pump wasn't working properly? I guess what is odd here is that the system *does* cool. Just not as much as it should. I can see the compressor turning, so it isn't a control relay issue.

ezone

Is the high side pressure low?
How did you test this?
Under what conditions?

Doug Lassiter

I never said I measured the high side. But if I did, and the high side wasn't high, then I'd have to ask why it wasn't.

Not getting too far here. I'll take it in and have it looked at.