SHaFT7

had our first hotter days last week, and I noticed something weird. Once the A/C has cooled the card to where it wants, it will cycle off like normal, but then it won't cycle back on for at least a few minutes. The vent temperature will climb past the temperature set on the climate control and sometimes it just won't come back on. You have to turn the A/C off and leave it off for 10sec or so, and then you can turn it back on and it will cool like normal.

I tested the pressures on the high side and low side and both seem fine.

If I set it to LO, it will cool all the way down and cycle off. sometimes it comes back, but more often it won't.

I usually have the climate control set to 69, and it was 95deg outside today. The car cooled down just fine, the vent temp (with a temp gauge) read ~49deg while it was cooling, which is great. when it cycles it immediately jumps to 60's and then starts a climb to 80deg. I had to turn the A/C off, wait 10sec, and then turn it back on to get it to come back. I had to do this 3x on the way home.

I'm thinking it's a sensor or something, as the compressor cycles on just fine, I just don't think it's getting the command correctly to do it again after it has cycled off.

ideas?

jda123

What was the readings on the low and high side for "fine"? At what RPM? What did they look like at 2500 RPM?

Take it off of "auto," put the fan all the way up, temp all the way down and it should stay on forever. If this happens, then it is likely an electrical in the cabin. Otherwise, maybe a pressure switch or something.

There is a temp sensor in the drivers lower dash about where your right knee would be when driving. Make sure it is seated correctly and did not fall out. Mine fell out once and the heat would never come back on.

SHaFT7

thanks, i'll check that. i bet it is the sensor.

SHaFT7

I found that sensor and pulled it out. It was full of grime and dirt. I cleaned it and put it back in and it seems to be a bit better.

But, then today happened: I was driving on the highway in severe rain and humidity. The A/C would shut off, even when I had it forced on, and it wouldn't come back on, even if I turned the temp down. It stayed off long enough for the windshield to fog completely up and I had to pull over. After 30sec or so I could turn it back on and it would be fine for the next 10min.

I could have put it on max cool, but then it would have froze us out of the car. I'm sure there has to be a sensor somewhere that's not telling it to come back on.

jda123

It could be the low or high pressure switch.

See if one of your local auto parts stores will rent (free) a set of manifold gauges. If so, Google how to use them... or we can tell you. They will give you the readings that you need to know.

SHaFT7

my pressure is fine. Like i said earlier, on super hot days I can put it on low and it will just go and go. today there was super high humidity. I also put gauges on it, and while I can't remember the high side number exactly, it was in the 250 area on a hot day. The low side never dipped below 35.

I put the a/c system in sensor-test mode and was able to see the evap temp sensor in realtime. it got down to 5C before the a/c cut out. once it went back up to about 20C, it allowed it back on. I think I may just have a cabin filter that is not allowing enough airflow across the evap, causing it to freeze up.

I just checked my last filter change and it was 2.5 years ago. I used an ATP charcoal filter, the HA5. I imagine that since this has charcoal in it, that it might flow a bit less than a normal filter anyway. Since it's over 2 years old, I went ahead and ordered another one. We'll see if that helps.

SHaFT7

ok, new filter installed, still having the issue. if i set the car on Lo, then it will run and run. if i set it somewhere normal, then when it cycles, it won't come back for around 5-10 minute, all the while the vent temp is climbing to 80deg F before it comes back on.

i'm thinking this has to be some sensor that's not telling it to come back on, but all the diags look good so far. no codes thrown either....

jda123

If you download the service manual, it has resistances for the temp sensors that you can test if you want. I got the manual somehow in the past, but I don't remember the details.

SHaFT7

yeah i've got the manual for it. didn't realize it had those values. will test.

SHaFT7

Long story here:

A/C this summer just doesn't work correctly. It will cool the car down to the temp that I set it too no problem. it can be 95deg outside and my vent temp will still say 40deg (on my stick thermometer in the vent) Once it cycles off, it sometimes won't cycle back on for awhile, and my vent temp will climb up to 80+ before it comes back on.

So, I started checking sensors. Everything seems to be fine. the 88:88 diagnostic showed no errors. The active diagnostics showed a problem with the passenger aix mix control motor, but cycling it all the way hot and then all the way cold seems to have fixed that and now it moves from 95% (full hot) down to B1 (on the scale this is 10% open, so i guess full cold)

I checked the evap temp while it was running and it will get down to 5C and it seems to cycle once it gets that low. My first thought is low charge, so I add some, but no dice.

Finally I figured it must be the expansion valve being stuck almost closed so that it can't let enough r134 into the evaporator to keep the temp high enough so that it doesn't freeze up.

I evac'd the entire system, replaced the expansion valve with a new one, new seals on the two sets of lines that go into the expansion valve, and evac'd again for 45 min. I made sure that it held vacuum at 26" for 20min before filling it with precisely 550g of r134. (we had a 30lb bottle with a digital scale to weigh it.) So, I know the charge was perfect.

I fire up the car, and it doesn't really act that different. At idle, it'll run about 35-50psi on the lowside. (full Lo setting). When I ramp the rpm to 2500rpm it'll drop down to 25psi and cycle off.

That seems to me that the charge isn't enough. We added just 0.1kg more and it didn't really make a difference.

All of the other sensors seems to be in range. sunlight sensor, ambient air, cabin air, all seem to be good.

If I drive around with the a/c on full lo, it'll run for quite awhile, much longer than if i set it to 75deg auto. (I'm in kansas and it's been 85+ with tons of humidity for 2 weeks now).

on 75auto, it will cool the right temp, and the fan speed slows down to maintain, and at that point the evap temp will drop to 5C and it cycles off. sometimes it comes back in 30sec, sometimes it's 4-5min. It doesn't take the car long to get real hot again.

The car always runs perfect when it's super hot and just started up. It always cools the car down to the right temp.

so, my question is, what the heck is next? I'm about to give up and take the car in.

SHaFT7

update: I was considering the possibility that the air mix doors weren't operating correctly so i removed the motors to test them and they all seem fine. of course the passenger side mode control motor is 100% impossible to reinstall and the actuating arm broke, which means i get to spend another $60 on this car that is wasted.

I hope someone has some ideas for me. I do not want to hand this over to the dealer and get a $1000 price tag to fix something small and stupid (which I know it is)

Kobeone

I'm not that great with ac's but first when u add freon I always go by the gauge not lbs. another thing is when you go by lbs the outside temp has to do with how you gauge it. When I would evacuate a system I always go -29. It kinda sounds like your compressor wont kick on when it's supposed to so if you have the right amount of freon temp switch maybe? Sounds like something is reading the int temp wrong and telling the compressor your at desired temp.

Sorry second sentence I meant gauge not lbs

SHaFT7

no, you never fill by the gauge from empty. this car takes a specific amount of freon from empty. 500-550g is the official amount that this car takes.

my internal air temp sensor is reading correctly from looking at the diagnostic.

Kobeone

I understand it may require a specific amount but what about pressure?

SHaFT7

pressures definitely drop more than I would expect. at idle with full a/c running and the outside being ~85deg with high humidity, the low side is between 34-40psi and the high side is around 210-225psi.

as soon as i rev it to ~2500 it will drop below 25psi, which is below 32deg F at the evap, causing the evap sensor to kill the compressor. This is somewhat confusing as I don't think I have a blockage as I don't have the high side spiking while the low side stays low. it feels like I just don't have enough gas in there, but I put in the correct amount.

Kobeone

It might be worth it to have dealership diagnose it. Not fix it just diagnose it. Prob just cost $50. U seem competent enough to fix whatever they say it is.

SHaFT7

interesting. for that price your damn right it's worth it.

Turbonut

iTrader: (1)

I know you said all sensors checked, Evap Temp sensor one of them?

SHaFT7

The evap sensor *looks* fine from the readings it gives on the live diagnostics test. I haven't actually pulled it out and done the water test yet to test resistance at different temps.

I called acura and for $50 they are going to diagnose for me, which is WELL worth it. thanks Kobeone for that idea.

Kobeone

No prob man good luck

vietxquangstah

iTrader: (7)

Please come back and post details of what you find!

I'm having slight cooling problems with my A/C on my 08 TL base.

I can set the temp to "LO" and fan speed on MAX and when I put a thermometer on the driver side middle vent it will read no lower than 58-60F. These measurements are taken when the outside ambient temperature is 85-95F.

Also, when it's 85-95F outside and I go in the car and start it up and turn the AC on "Auto 65" it will take literally 3-5 minutes before the inside of the car actually feels cool and "tolerable"

Majority of the time before I get to my car I use the key fob to open all 4 windows to let the hot air out and start the car and run the A/C system on Auto 65 for about 1 minute with the windows still rolled down so by the time I roll the windows back up it's still not very hot. It helps slightly, but my A/C system doesn't get cold (40-50F degrees) and it certainly doesn't cool the car within the 1st minute of turning it on like a brand new (or any car with a properly operating A/C system) should.

Any ideas?

SHaFT7

yeah i'll make sure and post back. i will be taking the car in next week.

My cooling instantly goes to 40deg, so i'm definitely having a different problem than you are. If you are having an air mix door problem, that could be it, it is not going full a/c but instead mixing heat in with it. Try running the temp all the way to HI and all the way to LO several times, as if the doors are just sticking a bit, that might free them up.

SHaFT7

also something new: I now have the occasional whoop! noise from the expansion valve, which is crappy. the old one didn't do this. I wonder if I should get another one or just put the old one back in. either way is a PITA.

chinesestunna

So I had a similar problem with my A/C last year, not sure if you're is identical:

1) The A/C was working fine, but started fading one day. First the compressor seems to not come on once in a while, then it became any time the car is stopped or driving slowly, eventually the situation deteriorated to the A/C will only come on initially when the car first starts and before it warms up in the morning.
2) I ran all self diags with the car, no error codes from ODB2 readings, tested the system pressure etc, everything seems fine.

I thought it was the compressor going out but as it turns out, it was just the field coil, check out this awesome replacement guide: https://acurazine.com/forums/3g-tl-problems-fixes-114/c-field-coil-replacement-guide-772614/

Word to the wise, I spent waaaay too much time trying to remove the last snap ring because the opening on mine is facing the front vs. the back and was blocked by the axle. DON'T try to force it off, just spray some WD-40 and rotate the ring in place and remove with snap ring tool. I ended up taking off the radiator fan, alternator etc and still couldn't reach it.

Good luck!

SHaFT7

yeah, i wrote that guide replaced my field coil 2x so far. it's fine as the compressor runs when the car is hot, it's just not being triggered correctly.

Nova_brad

I had a Kia do this to me one time and I narrowed it down to a faulty evap pressure sensor. Did so by removing its connector and building a resistor that is middle of the specification of the sensor...then the ac compressor cycled as it should and pressures acted normal on the gauges. This took me more than 1/2 hour aka 50 bucks to diagnose though lol. The way Kia designed this ac system, I had to pull the dash and evaporator just to change the sensor. The customer declined. Don't blame them as it was probably 1/2 the cars value in 1 bill.

chinesestunna

Lol! How did I miss that, thank you so much for the guide and sorry about all your A/C woes. Keep us posted what you find out

SHaFT7

novabrad: this car doesn't have an evap pressure sensor, but it does have an evap temp sensor. my next test tonight (while i'm still waiting for my replacement mode motor to show up) is to pull the evap sensor (which thankfully is super easy to do) and test it.

When describing the problem to Acura, they had mentioned issues with relays and power transistors. I've replaced the compressor relay already, but not the power transistor (which is also easy). I kind of doubt it is that since it is SO intermittant, it doesn't follow heat at all.

SHaFT7

update: the car is at acura now and I'm driving a brand spankin' new 2013 RDX with 103mi on it. damn this thing is nice.

SHaFT7

Ok it has been fixed. Acura went through everything and said it was the field coil. again.

so my car has eaten 3 of them so far. I went ahead and bought another one and installed it this morning, and as expected, the A/C is perfect now.

why oh why is my car eating field coils at the rate of 1 per year?!?!

field coil guide here for whoever needs it: https://acurazine.com/forums/showthread.php?t=772614

fixed here: https://acurazine.com/forums/3g-tl-problems-fixes-114/c-still-not-working-right-after-recharge-expansion-valve-860640/

Steven Bell

iTrader: (2)

Shaft, your two threads have been merged together. They are about the same subject.

SHaFT7

thanks

bryrock

Thanks for this thread and the lesson on field coils. I've got a 2007 TL that was cooling just fine (and consistently) up until about a week ago, and now I have the exact intermittent problem you've described. Car cools down great, then the A/C cuts out and lets it heat back up, then just when it feels hopeless it kicks back in. I've got a 30 mile interstate commute, and it can happen anywhere from 1-3 times in one direction. Had the same bad experience in a downpour, where I started to pull over because of severe fogging inside. As soon as I was on the shoulder the A/C kicked back in and got me all the way home.

Tonight I noticed it kicked back in just as I rolled over an uneven bump in the road. Perhaps that was pure coincidence, but maybe not, now that I've seen whereabout that thing is located.

I don't work on my own cars anymore, but I'll definitely send a link to this thread to my mechanic, and hopefully it might save me some snipe hunting.