A/C not working? Irking me, especially with the summer months upon us?

Sorry, here are the pictures!

Hi there, Ken,

Thanks so much for the diagrams and taking time to reply, greatly appreciated! I think I have a good grasp of the system now. However, my main concern was with the self-diagnostic climate control fault stating there was something wrong with the evaporator temperature sensor. As shown in my pic, I know where the sensor is and how to access it, however, the actual probe is located inside the HVAC box itself, which cannot be opened unless the dash is pulled apart. Or at least that's what I'm assuming. Is this the case?

And how exactly would I test this sensor? I heard placing a multimeter at the two leads of the sensor and measuring the resistance in ohms is how you test these. But I'm not sure what readings I should look out for.

Also, since it's a two wire evap temperature sensor, would any two wire evap temperature sensor from another make/model of vehicle still work? I would absolutely dread having to rip my dash apart, but if that's what's required then I'd do it. But I was curious if drilling a small hole in the front of the HVAC box, feeding the sensor through, then sealing the hole with epoxy would also work? The problem is, I have no idea what it looks like on the inside, so I don't want to accidentally drill into the A/C evaporator itself.

It's so tough finding information about this particular part, especially on my model vehicle (97 Acura cl 3.0), but any help would be appreciated, thanks!

Ken,

Thank you so much again! That diagram really helps, especially for testing the resistance. Thankfully, I was able to locate a new OEM replacement for my vehicle for dirt cheap, and it should arrive by Monday.

Question: the first picture you showed I believe is of a different era/model car (maybe second generation CL?). I attached a picture of what it actually looks like in my vehicle in my 1st post. The sensor is actually a very thin wire with a tiny probe at the end. Please see attached pictures. It looks different than most other evap sensors from other makes/models, where there's a long, plastic post that can be accessed from the outside.

Unfortunately, my evap sensor is fed through a tiny hole in the side of the evap box. I don't think there's any way to remove it without first opening up the evap box (and removing the dashboard), as it's attached to the actual ac condenser like you stated.

My thought (might be stupid, please let me know) is that if this replacement sensor erases the fault and makes my AC work again. That I'd simply drill a very tiny hole in the front of my evap box with a Dremel (it's just black ABS plastic). A tiny hole just large enough to fit and feed the head of the new sensor through. Even though the tip of the sensor may not be mounted on the stock location directly against the condenser, should this installation suffice? Perhaps the temps won't be 100% accurate, but they still should be fine enough to run the A/C well enough and safely, since the probe is still inside the evaporator and reading the ambient temperature inside(?)

Sorry for the longwinded reply. This is, for all intents and purposes, a beater vehicle, and the less time and money, the better. So, I understand this isn't the optimal way to fix things, but I "think" it should be, okay? Please let me know, thank you!

Thanks so much Ken, will do! I'll keep you updated if the replacement part arrives tomorrow.

In the meantime, while I have your attention, could I ask you about an issue I'm having with my blend door actuator unit (same vehicle)? Or shall I open up a new inquiry thread for that?

Thanks again Ken, have a great rest of your weekend!

Hi again Ken, hope all is well.

I received my replacement (brand new OEM) evaporator temp sensor today. Installed it with the sensor hanging out in the open (ambient temp was around 90 today). And unfortunately it didn't change a thing. AC compressor and fan do not engage. Same readout fault on the climate control display, though I'm skeptical that it's accurate in the first place.

I went so far as to test the resistance on both the new evap temp sensor and the old one. And both were well within range.

Now I'm stumped.

Here's everything that I know:

1) low side freon pressure is good (with ac compressor and condenser fan jumped). Around 30psi.90psi when the system is off. I've yet to get a reading on the high side port. Perhaps next?

2) I'm pretty sure the physical AC button/switch at the console is good. Because when I turn the AC on, the actuator behind the glovebox (located to the right of the condenser unit) activates and opens up a blower door, then closes it when I turn the AC off. So it's getting a signal.

3) Again, both the ac compressor and condenser fan turn on (and stay on) when both relays are jumped under the fuse box (near the firewall) on the copper pins. Also, the condenser fan spins when the radiator fan comes on (to cool the motor after running awhile). So I'm sure both are good.

4) Both blend door actuators to on the passenger side appear to be functioning as they should, and moving/activating with the proper commands

Just for fun, I tested the voltage on the relay sockets for both the ac compressor and condenser fans. The copper pins (3 & 5) ALWAYS read 13 volts. Doesn't matter if the car is off/on, or the ac is off or on. The leads are hot 24/7. Should they be this way?

Is there any other testing I could do on the sockets themselves to see whether or not the proper signals are reaching them?

I actually found an AC wiring diagram specific for my 1997 acura cl. As attached. I removed the ecm to try and test those 4 wires indicated. A27, A17, C5, D11. But unsure how to test them, or in what combinations. I think I'll have to find an actual diagram of the ecm for this. I assumed the blue plug pictured (other 2 plugs are gray) were for the cooling system, so I tested the appropriate wires (green wires being ground and red wires being positive) and got full time hot reads (12 volts) when the car was ON (doesn't matter whether ac was on or off). And 0 volts while the car was off. Not even sure if this is pertinent.

Sorry for the novel, but that's where I'm at. Please let me know if I'm in over my head, but I feel as though I'm checking off possible culprits slowly but surely.

Thanks so much again for your time!

Sorry, one last thing! Are both the condenser fan and radiator fan supposed to activate simultaneously when the ac compressor is turned on? Because when I jumped the ac compressor and condenser fans manually, the radiator fan never turned on.

However, both fans turn on when the vehicle is warm and trying to cool itself off. Odd.

Hi Ken, thanks so much again for the follow-up. I thought about the possibility of the climate control module being bad. Is that the physical button panel on the center console? However, if this were the case, then wouldn't that mean there wouldn't be any reactions when the A/C button is pressed? Because when it is, the proper diagram lights up on the lcd readout, the blower starts running, a small door behind the glovebox rotates (to the right of the evaporator box) to open up a vent. So, the A/C button is indeed triggering a sequence of events.

I'm going to try and test for a signal at the compressor and condenser fan relay sockets to see if it's at least reaching that point. I have a better grasp of electrical circuits now. I also found the proper pinouts for the ecu sockets so I can test for a signal when AC is activated. And also, finally know how to locate the ambient temperature sensor behind the bumper and test it. Will get back tomorrow with an update. Hopefully a more fruitful one. Thanks again!

Greetings again Ken,

Hope all is well. Sorry for the delay, the extremely hot weather has made it virtually impossible to work on the car in the driveway. However, I finally got myself a test light and went to work.

I've attached images again of what the relays for the condenser fan and A/C compressor look like. 4 prong each.

Unfortunately, I witnessed NO change in any of the pins when the A/C was turned on. Here is what I measured.

A/C Off:

Compressor Relay Pins:
A: 12v
B: 12v
C: Nothing
D: Ground

Continuity between A&D
Continuity between B&D

Condenser Fan Relay Pins:
A: 12v
B: 12v
C: 12v
D: Ground

Continuity between A/B/C and D

A/C On:

Exact same readings on both.

I will make a quick note, that the ONLY difference I observed is Pin A on the A/C condenser unit is grounded with the car completely shut off. But it switches to hot 12v as soon as the ignition is turned on.

I am unsure, but does this indicate to you some kind of potential short in the system? I'm just wondering what kind of functionality I 'should' be observing in the AC condenser relay pins if everything was good.

I'm really not too worried about the condenser fan relay's readings, because the fan kicks on every time the engine reaches 95 degrees Celsius. So, I know it's good.

Just to reiterate, the climate control self-diagnostic is still throwing a code for the evaporator temperature sensor. But I tested the OEM one and also replaced it with a new working one and it made no difference.

Based on the findings above, it appears that my problem still lies somewhere in the interior and not in the engine bay, correct?

With the attached wire diagram for my vehicle, I know the 4 wires to test on the ECM that control the A/C circuit, I just don't know how exactly to test them. I'm guessing all 4 are hot 12 leads when the A/C is turned on, so I'd just connect a test light to ground then probe each of the 4 individually?

Again, your help is greatly appreciated, thanks so much!

Thank you so much Ken, I truly appreciate it!

Ken, I just want to thank you again. You are an absolute life saver! After days of ripping things apart and testing sensors, you were right. It turns out the HVAC controller itself works, but while ripping apart the dash a few years ago, one of the plugs going into the controller was loose. All I had to do was push the plug back in and the A/C worked perfectly. Have a great one and appreciate all that you do for the community!