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2006 Azera Limited
141k milesReasonably competent and conscientious shade-tree mechanic here. I get that AC troubleshooting and repair are best left to techs certified in such. But I don’t believe I’m quite ready for their services just yet. I’m trying to determine if the AC problem I have with this car is within the scope of my ability. That said…
A few days ago, the otherwise reliable AC in our Azera stopped working. When the AC console controls are activated the tach shows immediate engine idle-up yet NO cold air comes out the vents. Under the hood, I can see the compressor clutch does NOT activate. The AC fuse tests ok. The AC relay tests ok; however, I do NOT hear/feel the AC relay activate… which may indicate the ECU isn’t sending 12v to the relay (more on this below). I climbed under the engine and disconnected power to the clutch coil, blasted the contacts with air and WD-40, then reconnected and tested–still no clutch.
Static system pressures are dead-equal at ambient temp; no detected pressure drop after being connected for 48hrs (see image below). Since the clutch will not engage, I cannot get dynamic system pressures. From what I’ve read here and elsewhere, equal static pressure @ ~100lbs between both gauges is normal.
The ECU (“PCM” in the shop manual) controls the AC relay. (I presume the RPM bump when I turn on the AC indicates the ECU is working correctly.) The service manual lists two AC system sensors that feed into the ECU–the “evaporator temperature sensor” and the “AC pressure transducer”. Failure of either may prevent the AC relay from closing (via the ECU), so I need to test these components.
I have the service manual in front of me, but surprisingly it doesn’t provide a t’shooting flowchart for the AC system. I’m open to advice for appropriate “next” procedures.
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You need to check for continuity in the AC clutch coil. It sounds like a burnt coil.Will the clutch engage, if you supply 12v and ground to it through the 2 wires ?
Like you said, see if the clutch engages when you supply current directly to it. If not, I’d look at the coil. While you’re there, test the wires that go to the coil and make sure it’s actually getting power.
I believe I have a bad coil.
With the compressor mounted, I ran 12v directly into the connector–no click. I checked continuity–open circuit. I’ve ordered a coil (oem:97641-3K220, and a clutch (oem: 97644-3K120–I am NOT replacing the pulley and/or bearing. Space is crazy tight near the compressor; I hope I can remove the four mount bolts and drop the compressor; clearly, I want to avoid opening the system.
Still, one question continues to vex me: Why won’t the relay click when I operate the A/C control?
Unless I am missing an indication of a feedback loop in the wiring diagram, I see no reason the relay would not continue to receive an actuation voltage from the ECU/PCM, regardless of the coil state. Given this uncertainty and without benefit of a proper scan tool, I have zero confidence that the A/C on this car is gonna work after completing the onerous chore of replacing the coil and clutch.I’m sorry, but I can’t help you with the relay. I’m not knowledgeable in that area. But on most cars, once you unbolt the compressor, there’s some amount of play in the AC lines, so you can move it around to get it into a better position. For my compressor, the best way to access it is to take off the front passenger side wheel, and there’s a little access panel under there.
I agree, sounds like you have 2 different issues.
First, if you isolated the comp coil, and it’s open instead of reading 3-4 ohms, then it is bad. You need to pull the connector off to test it, as the ground wire could be open & a misdiagnosis would be made for an open coil.
Second, there still should be a signal to the AC relay to pull in, or a ‘click’ as you called it. Test your relay by swapping with another same size relay in the box, or a new one, or using jumpers with it pulled out of the fuse box. If it is good, proceed on.
There will be voltage in two of the socket pins to that AC relay, even if the AC is off. Take a 12v test light or a volmeter and make sure. The ECU input is ground side switched to energize the AC relay pilot.
If you can’t Identify the ECU pilot signal/ground wire, then don’t jumper anything to ground. If you can, then jumper the coil ground side of the relay to ground with the relay partially installed. It should ‘click’ when you ground the jumper lead.
You can even use your test light connected to battery positive, pull the relay, put the probe in the relay pilot ground socket, & cycle the AC switch to see if the ECU is trying switch the relay to ground. DO NOT USE a 12v jumper to do this or you will cook the ECU driver!!
If it’s not, then the problem is further upstream in the AC control module, the temp & pressure inputs into it, or even it’s connecting wiring.
AC diagrams were sourced from BBB industries, and there is a TSB for resistance checking on your AC compressor coil too.
The relay is ok.
Early in my diagnostics, I tested both the fuse and the relay. I swapped the working headlamp relay (same part no.) with no effect on the clutch while the headlamps worked with the A/C clutch relay. Next, I checked for 12v constant to the relay at the junction block. The “30” contactor reads constant hot, and “87” shows continuity to ground, as both should. However, with A/C on high (at the console) I get no value from either “86” or “85”, the ECU pilot signal/ground connectors; thus my concern this may indicate an upstream issue, and which I mentioned in my initial post.Compressor Coil Testing.
My DVM reads ‘no resistance‘ and ‘no continuity’ between the comp case and connector. (I tested the comp coil with the compressor mounted, so my results include that caveat). The harness feed to the compressor clutch is ok. I get continuity from the contactor under the AC clutch relay in the junction block (a.k.a, “relay box”) to the pin inside the compressor clutch connector. I also ran a 12v feed directly to the coil connector with no effect.…test the wires that go to the coil and make sure it’s actually getting power.
The harness feed to the compressor clutch is ok.
I get continuity from the contactor under the AC clutch relay in the junction block (a.k.a, “relay box”) to the pin inside the compressor clutch connector.
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