AC Diagnostics

**CrUZida** · 01-12-2009, 10:57 PM

10 points for effort, a lot less for putting thought into it.

I pulled the sensor off, waved a screw driver in front of it, and got no response from the multimeter.
Then I realised that it wasn't attracting the multimeter.
Grabbed a magnet, waved that in front of the sensor, and got a voltage on the multimeter.

So, it turns out that the AC slip sensor is the opposite to a lot of Toyota sensors. It requires a magnet passing past it to work.

So I'm guessing either that they installed a magnet on the flexplate, or the aircon never worked.
My money is on the latter, but we'll never know.

So, I replaced the sensor with a spare 1UZ cam sensor I had lying around.
Its all installed now, ready for a test, but the battery is flat...

**CrUZida** · 02-12-2009, 01:35 AM

Great Success!!

Charged the battery, ran the car and the AC stayed on for at least 30 seconds before I shut her down.

Will have to go for a drive tomorrow to test, but at the moment it looks positive.

Thanks to all who helped.
Dale picked it like a dirty nose.

Its a new thing for me this speed sensor. Even the 1990 MA70 didn't have one.
Strange that this 1989 beast does.

**allencr** · 02-12-2009, 06:35 AM

If there's an over sensitive/bad low pressure switch on the low pressure/suction side, it would have that symptom, or a good switch with low freon level.

**matty12** · 02-12-2009, 11:48 AM

Its more of a denso thing i think,funnily enough a sc400 uses one but the ls400 doesnt.Good idea if you ask me,can possibley stop major damage.

**CrUZida** · 03-12-2009, 10:44 PM

And the new sensor. Works a charm, went for a 10 min drive the other day, aircon was nice and cold.

**wilbo666** · 03-12-2009, 11:03 PM

Interesting.

It would seem that the AC ECU doesn't care what RPM the AC compressor is doing, just that it isn't seized! (I'd be very surprised if the flex plate had just the right amount of teeth to match the AC belt ratio etc!)

Cheers
Wilbo

**CrUZida** · 04-12-2009, 12:24 AM

Likewise.

Reading the IS200 manual linked above it needed a 4 pulse/rev output.
I'm pretty sure the flexplate gives a 6 pulse

But yeah, I'm assuming basic function.

**madmont** · 04-12-2009, 08:15 AM

probably looking at the screws which hold on the torque converter
here is a picture of the setup on the compressor
there is a magnet on the piston which passes the pickup when it moves
can only give a pulse when the piston hits top dead centre