A/C Weak need diag help

[doug13c]

So when I bought the vehicle about 6 months ago it did not have any a/c I hooked guages up to the system and figured out it was low on refrigerant so I went to Walmart and got the a/c pro since I have had a good experience using the product before and my a/c worked fine then but I didn't use it at all during the winter since it was cold out and it worked fine for the start of the summer but now that it's 100 out it's really struggling or flat out barely doing anything I've noticed as I drive or raise the rpm's of the engine it works a bit better I have also noticed that when it's around 80 out it works just fine driving down the highway with ice cold air. I do belive the compressor cycled on and off when I first charged the system. I originally charged it to around 30 or 40 psi on the low side I hooked guages up to it today and I had mabie 100 psi on the low side I safely lowered the pressure to 50psi and I had absolutely no cold air coming out of the vents raised it to 60 or 70 psi and I started getting cold air out of the vents.

Here's a list of things i have noticed over time since refilling the refrigerant.

I hear the expansion valve in the rear hiss on and off not sure if I should be hearing it at all.

The compressor runs constantly when vehicle is running or when the *** in the cab is turned from the off position

The high side line gets extremely hot and I do mean extremely hot like almost to hot to touch for more than a second

I have no idea what could be wrong or broken my ideas are that the expansion valve quit or is wore out, the filter drier needs to be replaced, or the orifice tube is clogged

 

[Hamfisted]

Get a good AC manifold gauge set and see what your high and low pressures are when the system is running. Report back.

You'll need the manifold set, the quick connects, and the freon can valve ...
Yellow Jacket AC Manifold Set & Quick Connects on Amazon

 

[doug13c]

I honestly have no idea what I'm looking at

 

[Hamfisted]

Is that a picture of the gauges with the engine at idle and AC on ? Seems the compressor is a little weak, but hard to tell without actually doing further testing. Your best bet is to take it to a reputable AC shop in your area and let them evaluate it.

 

[doug13c]

Yes that is at idle I do notice a power difference with the ac on versus when it's off

 

[Motorcity muscle]

Before you first charged system did you evacuate system with a vacuum pump. If system was very low the system can **** in air which has moisture in it and will freeze TXV and will not modulate as designed.

 

[doug13c]

Before you first charged system did you evacuate system with a vacuum pump. If system was very low the system can **** in air which has moisture in it and will freeze TXV and will not modulate as designed.

I did not vacuum the system down but I do belive it had about 10 psi of refrigerant left in it

 

[Motorcity muscle]

As long as compressor did not turn on with 10 psi in it, you should be good. But if pump turned on it would pull low side of system into a vacuum and pull in air. If you have a gauge set, check the high side pressure, if the gauge reading is fluctuating, you have air in system.

 

[riphip]

Also borrow a shop fan or equivalent to place in front of the truck grill & set on high speed while ac is on. RPM should be about 2k. Check pressures, low (blue) should drop to around 28-35 psi & high (red) should be 225-250 psi. Your fan clutch may not be working correctly if temp/pressure does not go down w/o shop fan running.

 

[doug13c]

I know it's not the fan clutch since I had to replace it this past winter old one seized up yet I did replace it with one from a junkyard yet I can swing the fan by hand with what I would think to be the proper amount of resistance