1987 Subaru GL Turbo. AC Fan will not come on when air conditioning is selected. I want to make sure I'm on the right track after reading some old threads. I have attached a battery to the fan and it DOES work, correspondingly attached test light to fan leads, no light when AC on.  There are 4 relays under left knee, drivers side dash. They are not labeled and the wiring diagram I have for my Panasonic AC system does not match the wire colors.  Of the four I identified the AC compressor relay and instrument lights. I can't identify the other two ( colors: LY, LR, WG, RY  and B, B, BY, BW). But neither clicks when AC is selected on.  I think I need to just buy a relay and see if it works.

Am I at the correct location for the car's electric fan relay?

Does this sound like a logical plan?

~► http://www.ultimatesubaru.org/forum/topic/87523-how-to-swap-the-old-roundie-relays-with-standard-bosch-relays/

The relay in question is S0A438A426. It is not round. It is located in the engine compartment, right strut, firewall.  Funky looking relay, 4 prong, squarish, not round. Can this be retrofitted with replacement. I looked at Oreilly, Napa and Rockauto and they don't sell it.

Most, but not all 4 pin relays were interchangeable. The very early metal ones were different in some way. I toss them and rewire. Tons of old Japanese cars use similar relays. If you cannot get to a junkyard the part number you gave is a Subaru number and you should be able to buy one online.

I discovered the problem is the Trinary Pressure switch. (on the drier). The trouble is I can't source a replacement. Anyone one know where one? It turns on the compressor, but does not send power to the relay. I rigged a grounding wire so I can turn on the fan with a switch, not prefect solution, but I think it will work until I can fine a switch.

Bear with me, Im totally not familiar with the EA82T in any way. So my info will have to be generic.

Im guessing you have an engine driven fan also? If so the electric fan is there for a/c performance at low speeds not just additional engine cooling. No matter you need the fan working.

The pressure switch has 4 pins and controls (+) to the compressor clutch and (-) trigger for the fan relay? If you were wiring savvy enough to locate this issue, your more than capable of triggering the relay in a different way. Say, from the AC switch on the dash, or just wire tapping the hot for the clutch and to the (+) trigger on the fan relay. Then permanently ground the (-) trigger on the relay. It was not wired that way stock for a reason. Probably so the fan could be triggered by a temp switch in the radiator as well. If this is the case the fan should turn on when the radiator gets x-degrees hot, and a work around would be more complex. Not sure how this is wired so just giving you ideas.

The dryers usually have a schrader valve behind the pressure switch so the switch could be replaced without evacuating system. 

Edited July 25, 201510 yr by ihscout54

Is the pressure switch faulty, or doing it's job & telling you that there's not enough gas in the system?

When was the last time you checked? Could be that you've got a faulty seal or some other problem.

running the A/C with no gas is bad for the compressor, and that's an expensive item to fix.

Edited July 26, 201510 yr by wagonist