AC Inoperative, No compressor Engagement

Ric Owner/Technician New Hampshire Posted   Latest   Edited  
Updated
HVAC
No Dtc's
Blows Warm

Hello everyone, hoping to gain a little insight on this one and see if I may be missing something. This Corolla blows warm and the compressor does not actuate when the AC button is pushed. Same result when placed in defrost. no codes in the HVAC module or the PCM. I can manually activate the compressor for a brief (5 seconds) interval where the air does start to get cold. AC charge is present with about 85 psi static. Confirmed AC button provides 12 volts to the controller. I didn't see anything inhibiting operation on the PCM side. Pressure switch voltage at 1.4 volts with good ground and 5 volt reference. I think the Drive Pro may not be showing all the data pids, but I was wondering if you know of something that might prevent operation that I'm not thinking of. It's looking like a bad HVAC module if it's not being blocked. Any thoughts?

edit: 2011 Corolla with manual AC

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Brian Owner
Ohio
Brian Default
 

What year Corolla ?

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Ric Owner/Technician
New Hampshire
Ric Default
 

My apologies. i inputted the vin and assumed it would populate. It's a 2011.

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Joseph Owner/Technician
New Jersey
Joseph Default
 

Get to the control wire at the HVAC control head. Use a meter at the output wire. See what you read when it is off and then on. Should change usually 0-12v on those if memory serves. If it doesn't, you have a bad switch.

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Ric Owner/Technician
New Hampshire
Ric Default
 

I confirmed 12 volts to the module from the AC switch as posted originally. There is no output from the module to the compressor.

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Bob Instructor
Arizona
Bob Default
 

I'm sure you've done this already, but have you checked your pressure switches on high and low sides? I am one of those silly lots that refuses to condemn modules until there is absolutely nothing else left.

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Ric Owner/Technician
New Hampshire
Ric Default
 

From what I can tell, yes, those both look fine.

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Bob Instructor
Arizona
Bob Default
 

I'm not sure if they're just switches or transducers on that vehicle, but if they're malfunctioning they will give you this kind of trouble. Also, when you energized the compressor for 5 seconds, what did your low side pressure drop to?

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Robert Owner
Pennsylvania
Robert Default
 

Two wires = Switch? Three wires = Sensor/Transducer?

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Bob Instructor
Arizona
Bob Default
 

Generally speaking. I don't remember which on that particular system.

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Ric Owner/Technician
New Hampshire
Ric Default
 

There's a 3 wire transducer on the low side. I believe the high side sensor is in the case; I cannot see it but there is a data pid.

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Ric Owner/Technician
New Hampshire
Ric Default
 

Yes. Low side dropped and high side raised. Just as expected.

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Joel Diagnostician
California
Joel Default
 

I had one on those corrola, sama scenario than you, waaht I found i the evaportive sensor was open , in my case open = 5v , normally if the voltage goesunder 2.1 prohibit the A/c activation abdI belive if it goes abobe 3.8 v also prevet a/c I was plying with it with resistor box.

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Ric Owner/Technician
New Hampshire
Ric Default
 

Interesting notion. I don't have a voltage pid for that circuit but I have a pressure equivalent. It was reading around 100 psi. Went up slightly when commanded (5 sec pulse)

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William Owner/Technician
British Columbia
William Default
 

Hi Ric: You stated you hot fed compressor and it worked for 5 sec. How did you hot feed? Just power or power and ground. If isolated power and ground that comp should run until it locks up or blows pressure relief. If it only runs for 5 sec I would suspect a bad clutch coil. When you press dash activate buttons do you get power at ac clutch?

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Ric Owner/Technician
New Hampshire
Ric Default
 

There is a feature on the scanner that enables the compressor. If memory serves, it's a pulse width modulated signal; no clutch. It only activates for 5 seconds then shuts down. When the AC button is pushed, there is 12 volts going to the module from the switch. Still no compressor engagement. No codes

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Glen Owner/Technician
Illinois
Glen Default
 

Pin-out chart in SI has the voltage info for the A/C amplifier. DTC B1413 has a chart for the Evap temp sensor.

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Ric Owner/Technician
New Hampshire
Ric Default
 

Data pid for evap temp sensor is at ambient; appears to be what I would expect for an off condition.

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Ric Owner/Technician
New Hampshire
Ric Update
 

Thanks to all who contributed to this question. I've discovered the problem. Yesterday there were no codes. Today there was 1 code, B1479 which is for the freon flow sensor. Wouldn't you know it, the voltage was out of spec. SI states not replaceable and to renew the compressor. Operation was inhibited by the AC module due to the out of spec voltage (low). I haven't seen a ton of this type of…

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Bob Instructor
Arizona
Bob Default
 

Thank you for posting the solution.

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Jj Technician
Massachusetts
Jj Default
 

A little late to the party here, but this is becoming really common on Toyotas. For future reference the flow sensor shouldn't be showing under 3.7v with the compressor off, anything under that and the ECU will think the compressor is on. Around 4v is really what it should be reading with the compressor off. PIDs seem to be hit or miss on availability, sometimes I can read flow sensor voltage…

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Ric Owner/Technician
New Hampshire
Ric Default
 

Thanks JJ, I'll be looking at a few as they come in to gather some known good values.

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Samuel Technician
New Jersey
Samuel Default
 

Easy for me to say now...:) from experience I have found these clutchless variable compressors to be problematic at times...I was leaning this direction.....SUPER glad that you found the issue...always a great feeling to solve the head scratchers!!!!!!

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Brian Owner
Ohio
Brian Default
 

I just came across one of these, no ac operation, little to no difference in static to running PSI, someone just did a evac and charge, stated about .1 Ib low due to would not suck in. Here I scoped the green wire to the compressor and the amperage as well, I am hoping the customer comes up with the $$ for a compressor so I can recheck and see if any difference in the current or a a bump / hump…

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Jj Technician
Massachusetts
Jj Default
 

Out of curiosity, did you happen to check the flow sensor signal at all? It would be interesting to see the relationship between it and the solenoid. I wish I could be of more use but the boss doesn't like when I do fun stuff like this, have to check it and move on to the next with how busy we are during the hot season.

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Brian Owner
Ohio
Brian Default
 

No I did not! I wish I did, That would be cool to see. Still no approval to complete the job, (students family member vehicle).

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Brian Owner
Ohio
Brian Default
   

I only had a few minutes to scope the compressor after replacement. Definite difference in the current ramp, I do not know if this is due to low refrigerant or just bad compressor. Note I do not think that I properly zeroed amp clamp on retesting due to in a hurry. I will be trying to test more.diag​.​net/file/f3y0dj94a…diag​.​net/file/f5o7zh3ne…

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