Tried to post earlier, but don't think it worked. 2006 Accord LX sedan with 2.4l. Replaced ac compressor and condensor coil with new Denso. Replaced expansion valve and two rubber hoses with 4 seasons brand. Pulled vacuum and it held overnight. Put one 12oz can of 134a into the system. Im getting 45 degree air out of the vents. However, low side pressure is nearing a steady 100psi. High side is almost 150psi. I did not replace the evaporator coil. Any ideas why low side is so high?

2006 accord. Replaced compressor and condensor with new denso. Replaced expansion valve and 2 rubber hoses with 4 seasons. Pulled vacuum and it held overnight. Put one 12oz can of r134a and started the car. Low pressure side is nearing a constant 100psi. High pressure side is nearing a constant 150psi. I did not replace the condensor coil. Why low pressure so high?

 

Your system calls for 17.6-19.4 oz for a full charge, but I would expect low pressures on both sides if the system was undercharged. You are also getting good temperatures at the vents.

I'm wondering if you have your manifold setup correctly. Typically the gate valves on the manifold are setup to isolate between the gauge and the yellow fill/vacuum line. To say it better, if the blue gate valve is shut, the blue pressure gauge will only read from the low pressure a/c line. Also a shut red gate valve should only have the red gauge read only read the high pressure a/c line. I wonder if your pressures are equalizing through the mainfold with both gate vales open?

 

Those pressures in the picture are with both valves on the manifold closed, and engine running with ac on max. The only time I have the red valve open is when vacuuming the system. Could a bad expansion valve cause anything like this?

 

When the a/c shuts off, how quickly to the pressures take to equalize?

 

Well, I found the problem! My gauges have a blockage on the low side. I scrounged around and found a gauge to put on the low side and it reads 30psi. When I disconnected the bad gauge low side, it remained at 100psi. Something is blocked inside the manifold itself. Mystery solved. I finished charging and have 150psi high side and about 32psi on the low side. Air is cold!

 

Your pressures were strange enough with good cooling at the vents that I thought something was up with the manifold. Glad you figured it out and thanks for posting the fix.