Compressor NEVER comes on. If i jumper the compressor relay it does come on so wiring integrity is good between at least the compressor and the relay. Pressure is always 105 low side, 100 high side. This would indicate to me a bad compressor. My question is, why does the ECU never command the compressor on (Even if for just a second?) I don't know the logic of the AC amplifier but I would assume it would at least command it on for a bit to view pressure (Assuming the amplifier does monitor pressures?) Few questions

1. Does the AC amplifier monitor pressure and control the on/off of the compressor
2. Shouldn't the AC amplifier command compressor on at least for a bit to be able to accurately view pressure
3. Based on me jumpering the compressor and the pressure NEVER changing on either side, would you concur that the compressor is trash?

Thanks,

Dave

 

Here is the operation of the AC system in the 2010-2015 RX350. Your AC system may be low on refrigerant which is triggering the low pressure switch fail-safe that prevents the compressor from operating. I would check your AC system for leaks and then recharge the system if the leak is corrected or not found before replacing your compressor.

 

Thanks, so it does seem the AC amplifier does directly control the compressor. I guess the next question is, do all DTCs for this come via CAN bus codes or does it have a stand alone system to scan? I googled this and looked in alldata but saw nothing pertaining to this really. I do see DTCs for the AC system for the 2010 RX350 so I feel it's all part of the PCM scanning but am not entirely sure. Given there are no codes when scanning PCM, do you think it's save to assume there is no issue w/ any sensor or data the AC amplifier would use to command compressor on? If not, I'm pretty confident the compressor is the issue unless the AC amplifier is somehow commanding the compressor solenoid to not compress when I am jumping the compressor clutch relay and forcing compressor on.

BTW, that neural network control is a bit strange to say the least.

 

I would check the low or high pressure switch. If the AC pressure is too high then the pressure switch is probably preventing the AC compressor from working.

You may have an blockage in AC system that is causing the low side to have too much pressure which is triggering the high pressure switch and disabling the compressor.

The video has good points about the AC system and gauge readings.

 

I bypassed everything (high/low switches) by jumpering the clutch relay so the compressor is on by my command. If there was a blockage I should see a super low pressure or vaccuum on the low side (The compressor trying to compress refrigerant that has nowhere to go). With having equal pressures, the compressor is most certainly not compressing anything (blocked or otherwise) My question is, how can I know the ac amplifier is not doing something w/ this solenoid I see mentioned which may be preventing any refrigerant compression.
Dave

 

Too advanced an question for my limited expertise in automotive AC systems. My best guess is that the issue is more related to an blockage that is causing high pressure in the system and the high pressure safety switch to be triggered which is preventing the AC compressor to run. Where and how I do not know. The issue could be a bad compressor solenoid that is connected to the AC amplifier or the AC amplifier itself. I would start with replacing the Ac amplifier if I was repairing my AC system and then work my way to the compressor or solenoid if it can be replaced without changing the compressor.

I have at best just recharged an low AC system and solved simple leak issues like leaky o-rings or shrader valves. Anything else is above my skill level or knowledge.

If you have some good electrical troubleshooting skills then you check the connection in between the AC amplifier and AC compressor for any faults.

 

Thanks for the info. What service data do you have? Is it possible to get a copy of what you have? Think of a compressor like sucking a straw and blocking one end with your finger, you will create a vacuum. A compressor has a suction line (Low pressure) and the liquid line (High pressure) and if there is a blockage the compressor is just sucking, creating a large pressure discrepancy. That's not the case here. I have to assume that if I had any connection issue the CAN bus would report it but I have such incomplete service data on the exact theory of operation of this thing that I cannot fully make that determination yet. I'm not going to throw parts at it, that's for sure.

That relay is the relay I jumpered, basically applying 12VDC to the compressor coil. That pin 20 from the AC amp. is not providing a ground signal to engage the comp. clutch but I am unsure why. But again, unless that solenoid is somehow in a position not to allow compression, the compressor is not working at all. If I had the ability to monitor a compressor solenoid PID I could know the current commanded position of that solenoid.

Dave

 

You can gain access to the offical service manual at TIS.com for a fee or purchase an copy of TIS for your RX350 off Ebay.

Good luck with your diagnosis of the issue. I would just throw parts at it starting with the AC amplifier and then maybe AC compressor clutch if the refrigerant level check out fine without any leaks.

 

Thanks, I'm not a parts changer.. I located a service manual online, just need to translate the Russian. Once I can fully understand the operation of the ac amp. I can better diagnose this. I will probably see if I can get a scanner and a PID for the AC solenoid to command it to 100% just to ensure it's the compressor. Also may be a data PID to tell me what the values of the cutoff switches are.

Dave

 

If my 2015 Rx350 was not 10 years with over 190k miles I would not be a parts changer, but most of the parts are old on my RX350 so even if the part was not bad it is still 10 years old so and needed to be changed anyway before it fail sooner than later.

However, I understand your logic in properly diagnosing the issue and just swapping the confirmed bad component.

 

Generally solid state components rarely just "go bad" and need to be replaced and last the life of the vehicle. In fact, today it's very rare for electronics to fail. Especially those in an environmentally dry and vibration free environment such as the A/C amplifier. If anyone else has any insight/input I'd appreciate it. I did order a bidirectional can bus scanner which hopefully will let me try to command the compressor on and the AC solenoid PWM value.

Dave

 

I am going to say this and move on . The service manual states you must gain access to the AC amplifier and test the unit for proper voltage at the power connector. Therefore, you have to take apart the dash to access the AC amplifier just to properly test it. Hence why I would just replace it if I have to go to that much trouble to access it.

However, good luck with the scan tool method of trouble shooting the issue.

I have an Xtool D8 scan tool but it would better to use the Tech Stream software for the more detailed module work in the Lexus.

Just my opinion. Good Luck.

Note: I tried to use my Xtool D8 BT scan tool to access the AC amplifier and it did not work. The scan tool can control the AC actuators and compressor clutch, but not command the AC amplifier nor display it values even under live data. The service manual method is the only true way of testing the AC amplifier. Maybe you may have better luck with the scan you bought but I doubt it.

 

Here is your free English version. Enjoy!
Here

 

Thanks

Ok, I thought about this some more. The test where it checks for +12V when AC amp connector disconnected is basically just confirming continuity between F50-20 connector pin and pin 2 of the relay coil, nothing more. The AC amp must (assumption) pull F50-20 low when AC is on hence that other test w/ ac switch on/off w/ AC amp plugged in. I guess I'm left to assume if i have no DTCs that all pressure limit switches and other sensors are fully functional/within spec as there is no testing here other than to see if there is continuity on F50-20 and that it pulls F50-20 low when AC is called for. Based on the alldata diagram, that's the only logical assumption I have. I do know for a fact the ac amplifier is NOT pulling F50-20 low as it does not energize the relay coil. However, I also know that jumpering the compressor clutch (and confirming locked pulley) pressure stays at 100 high/low indicating it is NOT compressing. It's sad there seems to be no comp solenoid PID but hopefully the one I get tomorrow has that. Looking at the supported functions, I did not see it as a special function so that's sucky. It makes me feel like the ac amp is seeing 100psi on low side and saying, NOPE, that low side is too high, will not energize compressor solenoid to make pressure. I just have no indication that this is the case but it's all that makes sense unless we have a bad compressor AND a bad A/C amp. hopefully there is an ac compressor control PID. If that works, I have to assume the AC amp is good. I'm betting they both aren't bad.

 

I'm having the same issue with mine ,,my friend can turn it on with a scanner and it will run for about 10 minutes and it has power going to the Amplifier but not out,,did ypu solve this problem yet ? I'M at the point of changing the Amplifier but even a used one is 450 bucks and I'd like to change the right part and not guess
how did you get the magnet to stick..the housing is cast aluminum isn't it,?