e5c4p3artist

I've been trying to diagnose an A/C problem I've had ever since I bought my TL. Tonight I did some fooling around and here are the very strange results.

First, this may or may not be related to the overall problem, but the TL has four dash vents from left to right: #1 - near the driver door, #2 - in the middle but on the driver side, #3 - in the middle but on the passenger side, #4 - near the passenger door. My #2 vent doesn't work very well, no matter what the setting it only blows out a minimal amount of air. All the others work okay.

Besides that, here is the real problem, generally. The passenger side A/C works perfectly no matter what. Dual mode or not, it always works as expected. Auto mode or not, it always works as expected.

But ever since I bought the car, I noticed that sometimes the driver side A/C will go hot on me and sometimes not. Sometimes it works just fine, sometimes it goes hot while the passenger side stays cold. And when it goes hot, it is hot. Not "room temperature" like the vent is blowing un-heated air, but actually hot like the heat is on.

Here are the strange specifics that I found out by some experimenting tonight.

The driver side A/C blows cold if the passenger temperature is set to 65 degrees or lower. And it blows hot if the passenger temperature is set to 66 degrees or higher. This happens both when in Auto mode and not.

If the A/C is not in Dual mode, of course both sides read the same on the temperature display. If both sides say 65, cold driver side. If both sides say 66, hot driver side.

If the A/C is in Dual mode (this is where it gets really weird), the driver side will blow cold if the passenger side is set to 65 or below and hot if the passenger side is set to 66 or above REGARDLESS OF WHAT TEMPERATURE THE DRIVER SIDE A/C IS SET TO.

That's right, I can have the driver side set to "Lo" - as low as it goes, but if the passenger side changes from 65 to 66, the drivers side goes from cold to hot. I can have the driver side set to "Hi" - as high as it goes, but if the passenger side changes from 66 to 65, the drivers side goes from hot to cold.

So I can get cold A/C all the time, by leaving the passenger side at 'Lo' and controlling the fan speed - basically running the air conditioning like you would in a car that does not have dual-zone climate control. But the problem is still as annoying as heck!

Is this the strangest A/C problem you've ever heard? Any thoughts or suggestions on how to fix it?

Jackass

Had the same issues last year with my '05. The dealer had it twice looking at it and the only thing they came up with was that the freon charge was low. I ended up accepting that diagnostic since they didn't charge me for anything. As long as I don't engage the dual zone, everything behaves mostly normal now. But if I enable dual zone, it is hit or miss now if the driver side is the correct temp.

Turbonut

iTrader: (1)

As there are many components involved, driver's and passenger's mode control motor, driver's and passenger's air mix control motor, plus other sensors and transistors, might want to try a self diagnostic test to see if any DTC appear.

Turn ignition on
Press and hold the OFF button. While holding the OFF button, press the circulation button 5 times within 10 seconds. Release the OFF button and the self-diagnostic will begin.

If there are any problems in the system, the temperature indicator will light up the segment of (A through S) corresponding to the error. The temperature indicator will then alternate every second between displaying "88" (all segments lit) and error code (A through S). To determine the meaning of the code you'll need to the DTC troubleshooting index.

If there is no problem detected, the segments will not illuminate.

Turn off the ignition switch to cancel the test.

Each part of the "88" indicates, or translates to a specific letter, e.g. top of the first 8 on the driver's side is a C, top of second is a D, passenger side temp, top of first 8 is a L, etc. and each segment indicates a specific problem.

Don't have a scanner so can't load the detection code values, but just as an example, if the top of the first 8 is lit, that would translate to a C:

C-An open in the outside air temperature sensor circuit.

At least you can see if there are any codes to indicate a problem within the system.

e5c4p3artist

It's amazing the things you just don't know about cars these days. Turbonut, I performed the diagnostic steps you described. The result was the bottom segment of the first 8 on the driver side.

So there is a code which does indicate a problem. So you need a scanner of some sort to interpret this? There's not just an online list somewhere that will tell what this code means?

Thanks for educating me about this, at least I've got somewhere to start now.

Turbonut

iTrader: (1)

K-A problem in the driver's air mix control linkage, door, or motor.
Got to run out, so I'll check further when we return.

Jackass

Sweet!! Looks like I will be out in my car pushing buttons tonight.

Turbonut

iTrader: (1)

Here goes:
DTC B1235 or DTC indicator K: A problem in the driver's air mix control linkage, door, or motor

1-Clear the DTC by turning the ignition switch off, than to on (ll).
2-Operate the climate control system in several modes.
3-Check for DTCs using the self diagnostic or HDS.
Is the DTC B1235 or K indicated?
Yes-go to step 4
No-Intermittent failure
4-Turn ignition switch off.
5-Test the driver's air mix control motor.
1-Disconnect the 5P connector from the driver's air mix control motor.
NOTE-INCOPRRECTLY APPLYING POWER TO THE MOTOR WILL DAMAGE IT. FOLLOW THE INSTRUCTIONS CAREFULLY.
2-Connect battery power to the No.1 terminal of the driver's air mix control motor, and ground the No. 2 terminal; the driver’s air mix control motor should run, and stop at max hot. If it doesn't, reverse the connections; the driver's air mix control motor should run and stop at max cool. When the driver's air mix control motor stops running, disconnect the battery power immediately.
3-If the driver's air mix control motor did not run in step 2, remove it, then check the driver's air mix control linkage and door for smooth movement.
If the linkage and the door move smoothly, replace the driver's air mix control motor.
If the linkage or the door sticks or binds, repair as needed.
If the driver's air mix control motor runs smoothly, go to step 4
4-Measure the resistance between No. 4 and No. 5 terminals. It should be between 4.2 and 7.8.
5-Reconnect the motor's 5P connector, then turn ignition on (ll).
6-Using the backprobe set, measure voltage between No. 3 and No. 5 terminal.
Max cool-about 1.0V
Max hot-about 4.0V
7-If either resistance or voltage readings are not as specified, replace the motor.


Is the driver's air mix control motor OK?
YES-Substitute a known good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit.

NO-Replace the driver's air mix control motor or repair the linkage or door.

e5c4p3artist

Nice! Thanks!

Now where can I go to find this information myself? =)

shftl

Shop manual.

www.helminc.com

The TL owner's friend and companion.

carlosriosness

are the pics on how to get to the "drivers air mix motor" or at least where its located in the car? same for "drivers air mix control linkage" where is that located/ how can i get to it?

thanks for the info you already posted.

ekrekel

I'm troubleshooting a simliar problem on the passenger side. The air/mix motors are pretty much behind the left and right side of the stereo.

I think you can see the passenger side motor when changing out the cabin air filter(remove glove box and liner). You may also need to remove the kick plate to the left of the passenger's foot.

Haven't figured out how to get to the driver's side yet.

carlosriosness

thanks for the heads up, i have been lazy with trying to fix it since its been warm here in CA. but as soon as it starts to get colder i will want both sites to heat up.

ekrekel

Ran the self diagnostic (OFF + Recirc x5) and replaced the Passenger Air/Mix and Thermistor. That didn't fix it. The messages cleared, but it was still Cold on the drivers side and warm/hot on the passenger side.

The problem wound up being a Schrader valve leak on the High side of the AC system. $180 later it's blowing cold again. I read people recommending the Freon check, but couldn't understand why when it was blowing cold on the driver side. There's only 1 evaporator that I know of, I figure it'd either be hot or cold. Apparently my logic is flawed. I sill fixed an issue the climate control system thought it had so I don't feel too bad about the extra parts. I just absolutley hate taking my car into a shop unless it's something I can't or don't want to do.

Dash tore apart, getting to this point is pretty straight forward if you've ever replaced your cabin air filter. I didn't take pictures removing each climate control parts, but be careful taking this apart. There are at least 2 items in here that use the same connector. It can't be good to swap them. Most climate control components removed(on floor). One box had something to do with the throttle control, I left it connected and just dangled it on the floorboard. :


Pointing at the Mix/Motor. The one you can easily see with the green connector in this picture is the mode motor. Air mix is hidden below it, also with a green connector:


Air/Mix Motor, Evap Thermistor is attached to the gray plug below air/mix:


This is some pretty uncomfortable work. Basically using the passenger door jam as a lumbar support for portions of it, but it'd probably cost $500-$600 to have a dealer or mechanic do this 1-2 hour task

carlosriosness

where is the shrader valve located?

what exactly was your AC problem, ive noticed everyone's problem has been a little different.

mine:

both sides the AC gets cold. but the passenger side does not get warm/hot unless its on max heat. even at 79 degrees the passenger side is pretty much extremely cold. (while the driver side seems normal).

i dont want to replace unnecessary things (spend money i dont have), but i might just need to since i have read many stories where even the dealership was just replacing random parts since they didn't know what the answer to this problem was.

thanks again for the pics and information you have already given, its really helpful!

ekrekel

My problem was Cold on Driver side, Hot on Passenger side. Error codes showed Passenger Mix Motor and Evap Thermistor issues, I replaced both of those but didn't fix the problem. Checked the AC testing ports(schrader valves) under the passenger side of the hood. One if probably red, one blue. It looked like oil or something sticky had sprayed around the area, leak. I guess the higher pressure when it was 100+ caused the valve to leak a bit, but not let all of the freon out.

I may have had a similar problem to what you're describing, it's been like this for about 100,000 miles. I described it as an overactive AC. I can set the climate control to pretty much any temp between LO and 70+ and the temp coming out of the vents will be ~40deg.(LO). If I max out the temp to HI for a few seconds then back it down to something lower(70) the air coming out of the vent will be about right ~60 deg and the fan slows as I'd expect it to. I thought the Thermistor alarm was the culprit, but that doesn't appear to be the case. I haven't bothered to change out the 2 temp sensors(ambient in the front bumper area and cabin in the panel under the steering wheel.) Those may have something to do with it, otherwise I'm thinking it's the climate control cpu ~$200. Since I'm in Texas I don't mind an overactive AC unit, especially if my workaround continues to do the trick.

The passenger air/mix motor sounds like a possibility for yours. Especially if the driver side doesn't get "stuck" on max cool like mine. Check the codes.

Did you do the system check?
-Turn off Car
-Put car into ON position, but not running
-Hold Climate control OFF button and press Recirculate button 5 times
-Wait while system does it's thing for about 30-40 seconds
-If a problem is detected segments of the 88 88 passenger/driver temp level displays will blink.

vietxquangstah

iTrader: (7)

^^ Wow your vent output temperature is 40 degrees on a 90-100 degree day? Did you use a thermometer to get that reading?

I did a AC service at my job and my vents don't come out that low on a 100 degree day. Lowest is maybe 55-60 degrees

dcmodels

AC vent output depends on ambient humidity, ambient temp, and test conditions (doors open or closed, etc.). Here is the factory service manual test procedure for an RDX - probably similar for a TL - or check the TL FSM.

https://acurazine.com/forums/showthread.php?p=13955220#post13955220

ekrekel

dcmodels That's a nice read about the controled AC Testing. Thanks!

I haven't attempted to calibrate this thermometer, but I think it's pretty acurate. It'll read about 120-130 when I get in the car, almost instantly cools to 100 once air starts flowing, down to 60 within a few minutes. It may take a couple miles of driving before it gets around 40, but it has been doing it pretty regularly for the last 10 days since the re-charge. Here's a picture from today. Austin Humidity is pretty low ~30% maybe.

dcmodels

Thank you - for others reading this thread, the FSM test procedure is meant to be a *heavy-load* test, to test the max output ability of the AC system.

Sometimes people don't understand that simply checking the vent output while driving with the doors closed is not a good indication of the max ability of the AC system - and a yearly 10 minute FSM type test against a *first-test-baseline* value, can let you know if the AC system begins to loose efficiency, before any problem becomes serious.

nards01

how do I know if my system is running the test? I hold down "Off" and press the re-cir button but nothing happens....is there any way to know if it is working?

Yohan Yim

Did you solve the problem? I exactly have the same problem. 11+ Acura RL