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A/C Education please , Why 4 AC relays?


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1996 legacy  ej2.2  .  The A/C Compressor is not going on.  all fuses are good.  But it has 4 relays for a/c i swaped them on at a time with the headlight relay and nothing.

 

any tips or info would be great,

 

thanks

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There is technically only 1 AC relay for the compressor. 

The 4 under the hood labeled as AC relays are for the compressor, main fan low speed, main fan high speed, and sub-fan high speed. There is another relay in the dash fuse box for the sub fan low speed. 

 

The combination is used to vary fan speeds based on compressor operation and cooling need depending on engine temperature. 

 

 

Most likely reason for the AC to not work is the charge is too low due to a leak. 

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Something to do with AC functions needing different inputs at various times, should check your wiring diagram for the AC circuit to work out how its done ... Got a multimeter ?

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Something to do with AC functions needing different inputs at various times, should check your wiring diagram for the AC circuit to work out how its done ... Got a multimeter ?

i will check for power at the compressor.

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There is technically only 1 AC relay for the compressor. 

The 4 under the hood labeled as AC relays are for the compressor, main fan low speed, main fan high speed, and sub-fan high speed. There is another relay in the dash fuse box for the sub fan low speed. 

 

The combination is used to vary fan speeds based on compressor operation and cooling need depending on engine temperature. 

 

 

Most likely reason for the AC to not work is the charge is too low due to a leak. 

do you know what one is for the compressor ? i want to jump it and see if the compressor starts.  thanks

Edited by winginit
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Pretty sure compressor relay is the rear-most. 

Can also bypass the pressure switch on the drier with a paper clip stuck in the wire connector terminals. 

Can also jump 12v straight from the battery to the wire on the compressor. 

 

I don't normally jump relays because the ECU controls those and jumping the wrong pins could damage the ECU. 

Edited by Fairtax4me
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I pushed the shraider valve to see if it had pressure,  there was none.   so i replace all the rubber 0-rings in the system filled it with coolant the compressor kicked on. and i got 43 degrees at the vents.   i put the seat back an enjoyed.  Fixed !!

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