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Toyota AC Stator Coil Issues(Clutch Coil)

2026 Views 12 Replies 6 Participants Last post by  greeky510
Soo at this point I am stumped on my AC unit, got it cooling again but then it failed to pull the clutch in again, 04 matrix XR, pre part number changes(per what the parts desk told me by vin verify), I have owned this car for about 2 months now. AC clutch was not engaging. Checked the relay switch that sends power to the compressor was at 5v, did some digging around, pressure switch is good, ohm'd out the electrical coil in the compressor, came up open, no resistance. Switch on dash is also good, fuse in driver kick panel is good, blower is moving air. Ordered that part new from toyota, Ohm'd that too before leaving the dealership parts desk and before installing the part, 4.6 ohms, installed it with ease, did not loose any of the washers that are with the clutch, both snap rings properly seated. Rechecked the compressor for being properly grounded, good. Rechecked voltage at relay terminals, 12v, compressor clutch is engaged at this time. Let run for about 20-30 mins in idle, pressure is good, across the coil is 40'F, Las vegas ambient was about 90'F with cloud cover and humid, did not record the moisture levels. After the local driving, AC was able to pull down to 58'f +/- in the supply vent w my thermometer to measure the air temps. Fan for ac mode is running, no issues. Drove around locally, light to light before heading home, normal driving, not beating on my car. As soon as I accelerated to match highway speeds from 25mph to 65pmh, within a short distance I noticed my thermometer in the vent starting to rise in temps to ambient, which by then was closer to 100'F+ ambient. From then on no more cooling abilities again. Checked the fuse under the driver side kick panel, not popped. Getting 5v across the relay to pull the switch for power to the compressor again. Also when I jump the terminals on the compressor no audible click or tap sound of the engagement but I do have 12v across those terminals. Rechecked new Stator coil(clutch Coil) that I just installed for resistance and showed open. Checked from terminal to power wire for compressor for a break in the wire, good. I could not find any loose grounds either from the ecu area or engine compartment? I also have a brand new alternator in the car, that is less than a month old. Voltage reg is new and good also. The old alternator voltage regulator went out, I am assuming the over voltage fried the first stator coil. Anyone else experience this also? Trying to figure out what I missed or need to do or prevent before I purchase another coil from factory today? Below pics are the new and old stator before the install. I am just beat at this time. Have any other ideas that you guys can suggest or know something specific with the matrix's ac. I herd that the relay is majority of the issues but not this time, did the swap of another working relay horn and fog lights, both work properly with those components. I am not sure where else to look. Help a fellow new matrix owner. Thank you guys

My bad about the sideways pic. It will not link or download like how I took it and saved it.

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"Getting 5v across the relay to pull the switch for power to the compressor again."



Can you specify where the 5v was measured from/to.
BBBind.com has schematic of HVAC circuit.


5v indicates a high resistance in the circuit.
Power coming in and out for the coil side of the M/G CLT relay. 4th section on right of schematic. Terminals 1 and 2

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Given 12v on the coil relay #1 pin measured to ground the relay should close when ECM grounds pin #2.
If circuit resistance higher than normal then some of the 12v will be dropped in the circuit wiring/connection or ECM.

You can measure for voltage drop in the circuit to determine fault.
Ok then I will measure for voltage drop in the circuit wiring/connection and or ECM. So then now I am assuming that since the coil side of the relay was not fully 12v at all times, it was causing the coil to pull in and out, causing the stator to have a short or open windings? Though when the install of the new part was complete. I was receiving 12v at terminal 1 and 2 on the coil side of the MG relay w the clutch engaging, temps were pulling down. not sure if it was sudden accel to highway speeds that something lost connection with that caused the high resistance with 5v on the coil side that fried the stator again.
Understand that your main concern is clutch coil opening up.

Can you verify that there is a 10 amp a/c protection fuse in the circuit?


If the clutch was constantly engaged it could heat coil to a point were it opened up.
Possibly that the ECM is holding the relay circuit on when it should be cycling.
Measure the voltage at the ECM( from ACMG pin #2 to ground)). It should be 12v during the clutch off cycle and close to 0v during the on cycle.
yes, I verified the 10 amp fuse in slot 24 under dash is still good working condition.

I will also verify voltage at ACMG pin 2 to ground during on and off cycles for 12v and 0v.
Did you notice any signs of heat, like bluing on the back of the a/c clutch hub face? Perhaps oil on the front of the compressor?

If the magnet isn't pulling the hub in with enough force, the clutch can slip and quickly lead to an overheat that damages the coil. Have you checked voltage right at the compressor? (engine on, normal electrical loads on)
I had a similar problem at about 185K miles on my 2004 Corolla. What I eventually noticed was that after about 10 minutes of driving, the AC would stop cooling. I experimented and at idle on my driveway the AC would eventually stop. I then opened the hood and at idle the AC kept working fine without losing any cooling even after an hour as long as the hood was open. It was apparent to me that it was a heat issue causing the clutch coil to short out.


I was going to do what you did (replace the coil), but before that I asked Scotty Kilmer (when he used to answer questions via email) what I should do. He said just replace the whole compressor. That's what I did and didn't have any trouble after that and the car now has 355K miles. New Denso compressors were only about $200 online at that time (don't know what they cost now). Considering the price of a new coil and comparing that to a complete new Denso compressor assembly for only $200, it was easy to make the decision. Not sure what's going on with your coil, but just FYI.
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John, does Scotty Kilmer still answer questions any more. If so what is the address. Thanks.
Its not just the cost of the new AC compressor. You will need to vacuum and refill the AC system. The AC clutch can most of the time be replaced without removing or disconnecting anything (besides the serpentine belt). If i had no issues with the AC at all besides the compressor clutch, i would just replace that.
John, does Scotty Kilmer still answer questions any more. If so what is the address. Thanks.
No he doesn't. The only way is to go on his live broadcast that he does once a week on Youtube via Yahoo mtg or whatever it is. It's nearly impossible to get on as he can only answer so many questions during the 30 minutes of his live broadcast Q & A period. LOTS of people post questions and he can't get to all of them.


Its not just the cost of the new AC compressor. You will need to vacuum and refill the AC system. The AC clutch can most of the time be replaced without removing or disconnecting anything (besides the serpentine belt). If i had no issues with the AC at all besides the compressor clutch, i would just replace that.

Right, I do get that. If you've already got the equipment, or if you "rent" the equipment for free, then it doesn't cost anything more. Refrigerant is dirt cheap at Wal-Mart (less than $5 per can). It's just that and the PAG oil (OK...and the dessicant dryer too), and yes....it's much more work, but that doesn't cost me anything. As far as just changing the clutch, Kilmer told me not to bother with that as the new clutch won't be acclimated to the position of the rotation of the well-worn compressor and it can cause problems. That happened on a Gen 3 Camry when I just replaced the clutch. It only lasted a few hundred miles. I wish I had just replaced it with a new $200 Denso compressor (which I then did IIRC. I don't know how they offer a new Denso compressor so cheap compared to rebuilt, lesser quality aftermarket brands that are $300 to $450). But yeah, if you're strapped for cash then I understand your point. For me, it's a deal to get a whole new compressor, which means I won't have to worry about it for a long time, which is what happened to me and my Corolla. The Denso compressor is still running fine.
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Right, I do get that. If you've already got the equipment, or if you "rent" the equipment for free, then it doesn't cost anything more. Refrigerant is dirt cheap at Wal-Mart (less than $5 per can). It's just that and the PAG oil (OK...and the dessicant dryer too), and yes....it's much more work, but that doesn't cost me anything. As far as just changing the clutch, Kilmer told me not to bother with that as the new clutch won't be acclimated to the position of the rotation of the well-worn compressor and it can cause problems. That happened on a Gen 3 Camry when I just replaced the clutch. It only lasted a few hundred miles. I wish I had just replaced it with a new $200 Denso compressor (which I then did IIRC. I don't know how they offer a new Denso compressor so cheap compared to rebuilt, lesser quality aftermarket brands that are $300 to $450). But yeah, if you're strapped for cash then I understand your point. For me, it's a deal to get a whole new compressor, which means I won't have to worry about it for a long time, which is what happened to me and my Corolla. The Denso compressor is still running fine.
i definitely agree with you.
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