Nothing seems to work on A/C

This gets posted a lot but couldn’t find a post close enough to what I have so I thought I’d start one

I replaced the compressor pickup sensor, compressor, A/C amplifier, A/C fuses. Vacuumed and refilled Pressures are at 31 low, 200 high. But no matter what, I get the blinking light of death. Each time I replace a part it takes slightly longer for the light to kick on but without fail after 5 minutes it kicks on. I’m pulling my hair out over this. Help!

this all started when the clutches went bad when I was off-roading in Utah. Clutches got dusty and blew apart as I was driving.

 

What year is your truck?
Is the amount of time it will run consistent or random?
When it does it does the compressor turn on for a few seconds and then turn off with a flashing A/C light when you hit the switch?

The flashing A/C light is when the A/C amplifier does not detect a speed signal from the compressor lock sensor after commanding the MG CLT relay on.
Possible causes are:
Open or shorted wire(s) in the lock sensor circuit
Bad lock sensor
Internal problem in the compressor
Open or shorted wire(s) to the MG CLT relay
Open in the wire from the MG CLT relay to the compressor
Failed compressor clutch
Belt slipping
Failed MG CLT Relay
Failed A/C amplifier

 

It’s a 2013, seems to be fairly consistent as it never stays on past 15 minutes. It does fluctuate sometimes between immediately turning off and 15 minutes. The compressor kicks on pumps out cold air and then flashes. When I hit the button it kicks on blows cold and shuts off. I’m wondering if maybe the compressor I put in is the problem as I had to cut and connect the wiring from new compressor to to the factory wiring.

I also “ cleaned” the condenser by hosing it off in case it was causing some sort of pressure issue. Lastly it seemed my high pressure liquid line was really hot which I’m not sure if that’s good or bad. Didn’t check the evap coil though.

 

Why did you need to do this?
It's possible it's either wired incorrectly or one of your connections is bad.

You can check the Lock Sensor circuit at Pin 10 (Red/White) Connector IH1 behind the glovebox (3rd wire down on the left of the connector shown)
Meter connected between a known good ground and the Red/White wire when the A/C is turned on you should see it briefly go to 12v and then drop to about 2.59v and stay there while the A/C is on. This can't be used to tell if the sensor is generating a signal or not but it will tell you whether or not the circuit is intact or shorted to ground.

High pressure will not cause the light to flash unless the belt were to start slipping but it should open the high pressure cutout around 450Psi which cuts the compressor without flashing the light.
High side pressure is largely dependent of ambient temp, on a cool day it's going to be much lower but on a hot day with a hot interior you could see over 300Psi on the high side.

 

Lock sensor circuit is good, 2.31 v while running. Redid my connector on compressor. Still nothing. I’m wondering if it is worth returning my compressor pickup (not sure if that’s the same a compressor lock sensor) and get a new one from rock auto. Original bought on Amazon with good reviews but I’m nervous that I’m chasing this problem when it’s just a factory defect.

would there be a way to bypass the sensor temporarily to see if that’s the problem?

 

You could try another one at this point, it's impossible to know if it's generating a signal without an oscilloscope and the signal is quite subtle (about 0.5v peak to peak) even on a good one.

 

My 2005 would flash from time to time. I read somewhere on here to remove the ac relay from under the hood and bang it on the floor a few times. I did that and it worked flawlessly after that.

 

Yea the relays can fail, it doesn't happen very often but you can just swap the MG CLT relay with the Horn relay to rule that out.

 

I’m Beverly’s to buy another compressor with lock sensor for 294$ if it doesn’t work because you can’t return them. Is there anything else to test maybe the compressor pig tails? Voltage? Idk. I’m about 500 into this and getting annoyed. Is taking it to a shop worth it or am I just going to keep getting shafted. I’m selling this truck so I’m trying not to spend a ton.

 

@Dm93 how about a bad thermistor? I've had them fail open, causing the evap to ice over. But if it failed such that it was too sensitive, it would close shortly after cold started blowing across it.

Of course I'm not even sure these trucks have that hardware, freeze up may be prevented in some other magical way. But I figure it's worth asking the question.

 

What about your hi/lo pressure sensors?

 

Without a scope to see what the signal is doing about all you can do is check wiring integrity between the lock sensor and the A/C Amplifier.

The evaporator temp sensor and pressure sensor tell the A/C Amplifier when to cycle the compressor of, they won't cause the light to flash.

 

Ordered a new compressor I’ll keep you guys in the loop. comes with a new lock sensor too. I’m 700 into this I hope this works.

 

Ok update guys, A/C works now. The Amazon’s compressor made of “chinesium” was the culprit. Threw in a OEM one for 300$ and worked like a champ. Anyone who’s reading this to fix the problem, if you know the compressor is bad do not cheap out!!!! I spent $800 repairing this when if I would’ve spent $300 on a good compressor it would’ve been fixed! Thanks guys!

 

This is why I went oe. 2 months now and fingers crossed it’s working like a champ

 

Glad you got it going again, yea crap parts get so many people in trouble.