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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4906
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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AC clutch relay won't energize. Relay is good. Compressor

Customer Question

AC clutch relay won't energize. Relay is good. Compressor works when I jump out relay. Something keeping relay from energizing
JA: Has the clutch been slipping? Are you having any trouble shifting?
Customer: I havent noticed any other issues.
JA: What is the model/year of your Toyota?
Customer: 2006 Toyota Sienna XLE
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I've verified proper system charge, and operating pressures. Tested pressure switch/bypassed pressure switch.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Toyota Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. Does this AC control unit have an AC button?

Customer: replied 1 year ago.
Expert:  Toyota Service replied 1 year ago.

Does the light inside the AC button flash at times?

Customer: replied 1 year ago.
I've only noticed a steady light. I've put the controller into DTC mode and it flashes 00
Customer: replied 1 year ago.
AC will operate for about 5 minutes then the clutch will disengage. It will not energize on it's own again.
Expert:  Toyota Service replied 1 year ago.

More often than not, the compressor relay not energizing is because of a faulty RPM sensor that is on the AC compressor. The RPM sensor is a safety device. If the compressor locks up, the RPM signal is zero. The AC amplifier sees the zero RPM signal (it is compared to the speed of the crankshaft via the crank position sensor). When the compressor RPM is read as zero, the AC amplifier cuts the ground to the MG CL relay (this is the compressor clutch relay; the one you are jumping). I would recommend further diagnosis to the AC compressor RPM sensor; the only way to do this is via an oscilloscope to measure the pulse pattern. You may need a new RPM sensor. That would be what I would be doing in my shop; diagnosis of the actual RPM via a scope and most likely replacement of the RPM sensor.

Customer: replied 1 year ago.
Where exactly is the RPM sensor mounted? I've only seen one wire going to the compressor.
Expert:  Toyota Service replied 1 year ago.

the rpm sensor is on the side of the compressor.

Customer: replied 1 year ago.
OK. How long with that keep the compressor from running? Is there a time limit for the amplifier to reset?
Customer: replied 1 year ago.
What would be the next step if the rpm sensor was replaced and I still had same issue?
Expert:  Toyota Service replied 1 year ago.

As long as the RPM signal is not symmetrical with the crank position (I believe the RPM should be one-fourth of crank speed; or vice versa; I'd have to look). the MG CL relay is de-energized. There is no 'reset'.

Expert:  Toyota Service replied 1 year ago.

If the replacement sensor does not fix it, you may have a bad compressor. Since you do not have AC DTCs, the compressor may be the root cause.

Customer: replied 1 year ago.
I'm only finding parts for the crankshaft position sensor. Is that the same sensor?
Expert:  Toyota Service replied 1 year ago.

No. attaches to the compressor; dealer item only

Expert:  Toyota Service replied 1 year ago.

some compressors, the sensor is not replaceable. A Toyota dealer part dept can tell you if you give them your VIN #