Need a little help from someone with a service manual

[Jason S.]

Does anyone have a description on how the A/C compressor control works? I have the A/C Clutch control working and the A/C works, but I can't quite figure out the compressor control. It seems the stock computer has it on all the time... Any input?

Thanks!

Jason.

[TomsSVX]

no. There should be an input from the A/C unit and the ECU relays the output to the clutch to engage. I do not have my FSM's in front of me to confirm all this but from what I can recall this is how it is setup. The ECU can cut the compressor during WOT and overheating to act as a safegaurd

Tom

[longassname]

ac control unit and ecu control of the ac compressor is actually quite complex. Beyond off and on they also adjust the load put on the compressor. The compressor has a warbler plate which adjusts the throw of the compressor piston and thus how much compressing it does. The ecu will also change engine operation quite a bit according to the conditions in the ac system.

[Hondasucks]

Originally Posted by longassname

ac control unit and ecu control of the ac compressor is actually quite complex. Beyond off and on they also adjust the load put on the compressor. The compressor has a warbler plate which adjusts the throw of the compressor piston and thus how much compressing it does. The ecu will also change engine operation quite a bit according to the conditions in the ac system.

Wow I didn't realize that the SVX has such a complex AC system!
The Scion xD (And some of the other newer Toyotas as well) has no magnetic clutch on the compressor, it uses a swash plate to vary the stroke of the pistons in the compressor. When no compressing is needed, the swash place goes completely flat, so it just spins and causes no load on the engine. There is a breakaway in the pulley so that if the compressor siezes, the breakaway will shear and allow the pulley to still rotate, so all the accessories will still work.

[Jason S.]

Originally Posted by TomsSVX

no. There should be an input from the A/C unit and the ECU relays the output to the clutch to engage. I do not have my FSM's in front of me to confirm all this but from what I can recall this is how it is setup. The ECU can cut the compressor during WOT and overheating to act as a safegaurd

Tom

I have the input to the computer working. I have the compressor clutch output working, and the A/C works. However I need a description of how the A/C compressor relay works...this one I can't figure out. The ECU has the single A/C request input, and then two outputs for the Compressor. One for the clutch, and one the label as A/C compressor relay.