'05 TL. The A/C started acting up. It works the first 10 minutes of the drive, but then blows like it was on vent never recovering until I park it. It doesn't matter if I turn the AC on and off and all the control options inside the vehicle. I replaced the relay and nothing changed. I put some gauges on it and the pressures are a bit low (i think). It's 95F outside and I am reading 40 PSI on the Low side and 180 PSI on the High side.

I'm not sure if the evaporator is freezing up or not. Is there a good way to determine if it's freezing or not? I checked the cabin air filter and it was pretty dirty. I haven't changed that yet.

What are my next steps to troubleshoot? When the clutch is not engaging but should be - do I check the pressure sensor voltage? If it's a clutch field coil malfunctioning, would it be so consistent with working in the first 10 minutes?

 

is the underhood fan (fans) running with the A/C on? sometimes the fan relay takes a dump and causes it not to turn on causing your issue. How much water drains out the car after you park it? If it's a LOT of water then its freezing and thawing and draining. Have you ever charged up the A/C on the TL? If not it's probably low!

Also clogged cabin filter limits flow over the coils causing it to freeze! Change your filter too! Don't use Bosch hepa filter, it'll break the A/C system bc it's so restrictive.

 

My 05 TL did the same thing when the field coil failed on the A/C compressor. I could get about 10-15 mins of ice cold air and then nothing, then wouldn't come back on until the car cooled off a bit. I did all the normal easy test (swap relay, check for the evap freezing, etc...) I then used my multi-meter and checked the resistance on the field coil when the compressor quit engaging and found it was infinite (meaning it wasn't complete) and the basically told me what I needed to replace.

If you don't have a multi-meter or don't want to cram your hands down by the compressor to get to the wiring for the field coil, you can "jump" the correct pins on the compressor relay when the car is hot and the compressor isn't engaging (make sure the car is off) and listen for click. Since you are jumping power directly to the field coil from the underhood fuse box, if it clicks then you have a relay issue or another issue such as pressure. If it doesn't click, then there is a good chance the field coil is gone.

Or you can take it too an A/C specialist shop and let them figure it out, I found a good one near me when I was having other issues with my A/C after fixing my field coil and they figured it out in like thirty minutes.

 

Check the simple stuff first. Replace the cabin filter and make sure both radiator/condenser fans are coming on when you turn on the AC. Both of them should come on when you turn on the AC, regardless of the temperature of the engine coolant.

 

The high side should be closer to 240 psi.

I'd add some more R134a. Do not go above 255 psi.

 

Thats what has me curious. I was tempted and added about 1-2 ounces of refrigerant but the pressure didn’t seem to rise. However, when I took the gauges off I noticed that the low side kept leaking a small amount. It seemed to my little brain that those valves should instantly seat and there should be no leakage. I just replaced that valve about a year ago (maybe 2). I’m not sure if that’s been the problem OR did operating the valve initiate the issue. My wife reported today that the AC held up better than it has. Not sure if it’s bc I added some R134 or bc I vacuumed out the cabin filter (which was quite restricted btw). I’m planning on changing the cabin air today.

 

Let me clarify because I don't know your circumstances and I might be giving you bad numbers.

The pressure will depend on both the air temperature and humidity.

Use this to help you:

 

I wanted to provide an update: PROBLEM RESOLVED!

I replaced the Relay, but the relay was fine. I replaced the cabin air filter, but I didn't think the evaporator was freezing up... that didn't change anything. I ran the A/C until it did not work and cut off the car, jumped the relay and got no clicks on the clutch. I unclipped the red/blue wire from the compressor and had continuity back to the relay box. But of course it had continuity since the A/C ALWAYS worked when the car was first on... that's not electrical. Reading through 05ACURATL's posts and the replacement guide, I was pretty sure it was the Field Coil. Especially since the resistance has to be measured at a certain temp, meaning that temperature changes the resistance of them. I was reading infinite resistance/non-continuous from the relay box. So I bought a field coil.

The initial gap was around 0.89mm/35 thousandths (I had US feeler gauges in thousandths so I had to convert.) It needed to be between 13 and 21 thousandths.

The replacement was a bitch. The Iwin 13-1/4" Compound, long-reach bent nose pliers were a life saver for both snap rings. I had the largest pair of snap ring pliers lowes sells and they were worthless, not opening wide enough. I also recommend some sturdy picks... not sure if these are flimsy but this is what I mean. I put the pliers closed, in the opening of the snap-ring and spread the pliers, pushing the ring open. Then used the pick and a thin flat-head to get underneath the ring. Then used the pliers to grab it. At that point, you pull hard and use a pick to work the opening around the shaft.

The pulley was also very much a pain. I had a 2ft pry bar (I needed a 3-4ft) and put it behind the pulley in the center. Then I tapped back and forth and I pulled directly on the pulley with the other hand. I eventually picked up a set of 2-jaw bearing pulllers from the brother. You can't attach them straight on, but I nudged it out enough to finish the pulley off with my hands.

I replaced everything, and got to the shims. I had too wide a gap but the field coil came with about 0.90mm/35 thousandths in shims (5,10,&20 thousandth intervals). The one thick shim that was stock was about 55 thousandths, so I replaced it with the 35 thousandths worth of new shims, cutting off 20 thousandths. I added the center bolt (using a 12V 1/4" Impact Nut Driver) and had good rotation and a nice gap, around 15 thousands or so (around 0.38mm).

That washer tank was a bitch to get back on... I couldn't tell if it was b/c it was late and I was heat exhausted, but I couldn't for the life of me get it back right. I just mashed in 2 of the bolts and called it a night. . Started the car up, and A/C worked. It took me 5 hours - but I did stop for dinner and entertaining the baby a few times, and 30 minutes to pick up the bearing pullers. I'd say 3.5/4 hours of straight work.

My wife said the next say it worked like a champ! Extra lovin' for me! Cheers

 

Glad to here you got it working! I know when I changed mine the snap rings were a massive pain, I was able to get them on and off with a pick and a decent set of snap ring pliers. I guess I got lucky with the pulley/clutch assembly, it slid off with ease and went on the same. I am pretty sure I set my clutch gap at a similar spec, I tried to go towards the lower end of the range since the gap will only get bigger over time.

 

My thoughts as well. I appreciate your help - your thread from a few years back was the one that got me on the trail. I was sweating having a bad compressor or some other big A/C issue - with this car at 229k and my wife needing a new car any moment if we get pregnant again, I was thinking this might be it. whew!