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AC Repair Diagnosis, Evaporator core Expansion Valve??

3K views 4 replies 2 participants last post by  beef tits 
#1 ·
Hello, 2003 xterra 88K 3.3l. So I've been trying to diagnose my AC problem. No cooling at all a groaning or grinding from under the dash/glove box, compressor cycles on and off continually, fittings on the compressor lines don't seem oily and the evap sensor has been replaced. Also when I got it it didn't have the cabin filters installed just tape over the hole. Also the heat doesn't seem very warm in the winter but that could be a separate issue. I've read about the evaporator core and the expansion valve issue, how can I diagnose this? Many Thanks!
 
#2 ·
Any thoughts? My evaporator core looks clean on the passenger side and I can't find any trace of oily stuff on the lines. The grumbling and groaning seems to indicate something. I'm also going to do the 100k at 88k as the water pump seems to be leaking. I'll check in soon, Thanks!
 
#3 ·
Any thoughts? My evaporator core looks clean on the passenger side and I can't find any trace of oily stuff on the lines. The grumbling and groaning seems to indicate something. I'm also going to do the 100k at 88k as the water pump seems to be leaking. I'll check in soon, Thanks!
Get a gauge set and check pressures when its cycling.
 
#4 ·
Back again, looks like 39 on the low side and 95/110 on the high. Again no obvious leaks and groaning from under dash, compressor cycles on and off quickly. Can the expansion valve get clogged etc.. My X didn't have cabin filters when I got it just tape over the hole, I've replaced the thermo sensor and the evaporator core seems to be clean but can't see all that well. Thanks!
 
#5 ·
A few things I would try to figure out;

Is your TXVs normally open or normally closed? - Regarding the gurgling noise, it sounds like liquid refrigerant may be making its way into your coil (through a failed TXV) I assume you have checked that the noise is not the fan motor? If liquid refrigerant makes its way to your compressor, your compressor will be toast. I would start diagnosing that TXV, figure out how it works. Is there a screen? Is it clogged? Is it always open and cannot close?

Was "leak sealer" ever put into the system? This can cause all kinds of problems - like a TXV to fail from all the gunk and build up the "sealer" provides in the system. Don't ever use this shit.

Your high side pressure seems low. Note this is a residential chart but should be the same for automotive. The properties of the refrigerant don't change.

It's possible you have a bad compressor too. They normally cycle to maintain head pressure (high side). If it's not meeting a normal PSI and cycling on and off, something is not right.

Here is an 134A pressure chart for reference.

http://acprocold.com/faq/r-134a-system-pressure-chart/

And a how-to for TXV diagnosis

http://www.achrnews.com/articles/114393-ice-breaker-diagnosing-a-defective-txv
 
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