Super weird Yaris 2003 A/C problem

[zoharby]

Originally Posted by CoryM

Assuming that is true, you know it's not a control problem or electrical issue.

But when connecting the compressor directly to the battery (i.e. disconnected from car control completely), it doesn't happen.

My guess is that when it happens it receives a lower voltage (e.g. 3-5V) that is enough to power the LED but not enough for the the compressor clutch to lock.

After some more experiments, it does seem to be related to the throttle pedal, so maybe it is related to the throttle position sensor. If I give a quick stronger push on the gas pedal at neutral (but still far away from fully pressed) I seem to be able to trigger it at neutral. Or maybe related to the high pressure sensor.

The A/C guy gave up on it (he doesn't know enough about the electrical & control system...). I will head to the main Toyota shop next week and will ask them to hook a volt meter on the compressor line, maybe it will show the voltage dropping when this starts.

[CoryM]

OK. I read " Compressor is still getting power (they put a LED on the line which stayed on)" and figured that the compressor clutch was locked at that point. Did you see the compressor clutch disengage while it still had power going to it? If so (and I would be surprised if so), it's probably a low-current issue such as a bad driver or similar. If the clutch remains engaged when you lose cooling, it is not a control issue.

Esse10: Yes the condensor needs airflow. But I think we have that well covered since the issue occurs while driving at 50kph. I was just making the point that so long as the compressor is spinning, it is definitely not a control issue. If you are getting picky, you also missed a bunch of other mechanical things the a/c system needs to operate.

Cheers.

Originally Posted by zoharby

But when connecting the compressor directly to the battery (i.e. disconnected from car control completely), it doesn't happen.

My guess is that when it happens it receives a lower voltage (e.g. 3-5V) that is enough to power the LED but not enough for the the compressor clutch to lock.

After some more experiments, it does seem to be related to the throttle pedal, so maybe it is related to the throttle position sensor. If I give a quick stronger push on the gas pedal at neutral (but still far away from fully pressed) I seem to be able to trigger it at neutral. Or maybe related to the high pressure sensor.

The A/C guy gave up on it (he doesn't know enough about the electrical & control system...). I will head to the main Toyota shop next week and will ask them to hook a volt meter on the compressor line, maybe it will show the voltage dropping when this starts.