O'scope on the two pins from the a/c compressor speed sensor. Positive and negative excursions were 350 mVolts into a 1 Kohm load resister. Removing the resistor allowed the sensor to produce about 400 mV. You can watch a video of the A/C speed sensor when I manually apply +12 volts to the compressor clutch to make it run. |
After the pressure was brought up to about 200 psi, I disengaged the clutch and the pressure settled back to about 165 psi. I decided these readings didn't mean mutch since it was about 45 degrees F at the time. |
This shows the high pressure side pressure meter hooked up and a yellow test wire in place, being used at this time to energize the clutch coil. |
Leaning over the driver side of the front wheel looking at the relay and fuses. I removed the relay and stuck the blue electrical connectors in place so I could grab the connection better with a pair of aligator clips. The fore/aft terminals are the relay coil, with 12v on the forward terminal. The inboard/outboard terminals are the relay output. |
Once I confirmed the relay was not working, I decided to cut it open and investigate. Anvil, chisel, hammer... Notice the original one is 90987-02022, which has a coil that the computer can barely turn on. It tries, but then quits with the blinking green light on dashboard control. Toyota service bulletin EL011-05 (6/3/05) says to replace with a 90987-02028 relay, which activates easier. |
Silver legs energize the coil to magnetically operate the contacts. Put 12 volts across the 170 ohm coil (silver legs) and you should hear a "click". The copeper colored legs are suppose to close with low resistance. This relay clicked fine, but made no contact between the copper feet. |
Fuse and relay map inside the lid of the fuse box. The relay we care about is labeled "MG CLT" for MaGnetic CLuTch. |
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Once the rotor was out of the way, I tapped on the wheel stud with a hammer to slowly back it out. I positioned the new one and in order to pull it through the hub and lock it in place, I piled a stack of washers and then torqued the wheel nut onto the bolt. As I tighted upward of 100 ft lbs, the stud pulled into and mounted firmly in the hub. |
This shows the wire I used to short the outputs of the A/C relay. |
The black wire goes to the compressor clutch. The two grey wires are the compressor speed sensor. |
The paperclip receives 12v from the A/C relay and the red jumper delivers it to the compressor clutch coil. |
Red wire enables the compressor clutch; the white and black jumpers bring the speed sensor out to an oscilloscope. |
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