AC issue has me puzzled

Finally was warm enough to turn on the AC and nothing happened on my 2011 4cyl, 4wd. Performing some diagnostics I confirmed that the compressor clutch was not engaging. Checked the fuse - fine. Swapped out the relay - no dice. Disconnected the positive wire to the magnetic clutch and measured 5 ohms. Applied 12V and the clutch engaged. I must have a wire issue? Where should I begin?

 

Is your A/C light flashing when you turn it on?

 

Have you put gauges on it to determine the low/high?

 

I second the above ... Make sure you have adequate refrigerant. If it is low the clutch will not engage.

 

The system comes from the factory with green dye in the refrigerant. If you don't have access to a gauge set, look at all connection and if you see any green dye, you may have a small leak. There is a sensor below a certain pressure and the clutch won't engage

 

Does it turn on in HI? Does air come out at all it's just not cold?

 

OP has left the building it seems...

 

Sorry everyone, I didn't know that I had responses! No flashing lights and I don't own gauges. It does turn on in HI but clutch not engaged and no cold air. I don't recall any green dye anywhere. I didn't realize that the clutch would not engage with low pressure.

 

the larger refrigerant bottles in the autostore have guages on them.

or just buy a guage for $20 that is capable of using a bottle to fill. (just in case you need to fill)

if your system is not low, then it's either the wiring or the compressor doesn't work because it's shot. you already checked the relay and fuse.

have you done something recently that would damage wiring? bumpy road?

do you often get coroded connections from salty water or air?

 

Be careful using the gauges that only hook to the low side to charge a system, without looking at high side pressure as well you don't have an accurate representation of system charge and performance. It can be used as a quick guide as to whether the system is empty or not but it is not reccomended to top off a system with one as you can easily overcharge it.

 

yes, good point. also, you can only get an accurate reading while the system is on, which could be a problem since your compressor doesn't come on.

did you try hotwiring the compressor???

just go through the back door. jump the battery right to the compressor. if it comes on, then you know you have an electrical issue somewhere

 

First thing I would do is check static pressure (psi should be about equal or slightly higher than ambient air temp) as the system will not turn on if the pressure is below about 28 psi.

 

The most likely culprit is just that it's just a little low on charge.
If you were able to check A/C failures for the last 20 years and compile them by failure mode, low charge would win. I'd damn near bet my next paycheck on it.
Don't mess with anything else until you've verified it is sufficiently charged.
And I don't think I believe that they all came from the factory with the green dye in the system. I've charged a handful over the years and have never had green dye burp back out at me when I disconnect the lines.

 

I can confirm that dye is not always added from factory. I replaced a condenser in my 2015 that had a leak on the edge of the condenser. I first check with uv light at night, nothing. Then check with gauges, low, so recharged with a little dye, and a few days later, bam! Here’s the leak. So all these post that people make that there’s dye at the factory are clueless.

 

You guys have given me great information! I found a friend who has gauges and I will check the pressure and see what I find. Thank you!

 

Also, check that the pressure switch is not AFU. Unplug and put a jumper across the connector.

 

It turned out that the pressure was low. I'm all set now, thanks everyone for all of the help!

 

Hope you fixed the leak. Or have plans to at some point.

 

Also a good way to make a problem worse. That's not a diagnostic, it's a bypass. If the sensor was ok, and you bypass it like that to force it to run. I'll bet my next 2 pay checks more will be broken. I ran a beater like that, hoping to just ram cans of refrigerant in and bypass the switch just to make it a couple weeks before I crushed it. I believe I made it roughly a day and a half.

 

Nope. Perfectly valid approach to testing that sensor. Normal part of diagnostics. If you continued to "ram cans of refrigerant" into the system thinking that was fine, that is on you. A failed pressure switch will not affect refrigerant charge.