I don't have the Toyota Factory Repair Manual for a 1984 Celica, so I don't know the control for your A/C system. I have a 5th Gen Celica with the Factory Repair Manuals. I can tell from how you describe your control system that it is different than mine. Regardless, did you remove your original pressure switch from your A/C system? Did you install your new pressure switch on your A/C system?

For awareness, I'm pretty sure (not positive) that your A/C pressure switch is normally open (meaning no continuity) when not installed, as it is only sensing atmospheric pressure. An open switch will not allow the A/C compressor to turn on. You need pressure in your A/C system (which is present when your A/C system is properly charged) to cause the pressure switch to close. In a closed state, the pressure switch should allow your A/C compressor to turn on. If you did not remove your old pressure switch, and you have no continuity at the pressure switch, I would suspect you lost your refrigerant charge and no longer have adequate pressure to allow your A/C compressor to turn on.

 

Thanks for the insight!

Yes, as I mentioned in the Work Performed section, I DID replace the pressure switch. On the 84, the pressure switch is inside the evaporator box. I'm not sure where it's located on other models. Because of where it is on the 84, you have to disconnect both the lines that pass through the firewall in order to remove the evaporator box and gain access to the switch.

I did that, reinstalled the evaporator box, and then performed a vacuum test, which it passed.

I then tried to recharge the system, but it won't charge (assuming) because the compressor won't kick on.

QUESTION: If i have to depressurize the system in order to replace the switch, and the system needs to repressurize to kick on the compressor, but it won't kick on because the switch needs pressure in order to turn the compressor on, how am I supposed to recharge the system? What am I misunderstanding?

 

You do not need to have the compressor running to put in refrigerant. If you can't add refrigerant, you either have a defective setup to add refrigerant or your port valve (the port you are trying to add the refrigerant to) is defective and won't open.

You must have the system drawn down by vacuum first before adding refrigerant. That vacuum level is extremely low (measured in microns) to ensure there is no non-condensible gas (like regular air) left in the system, and that all condensible material is evacuated.

 

Again, thanks.

As I stated, I'm pulling a vacuum. But to further clarify, here's how I'm doing it. I'm drawing a vacuum down to -30 (although even after an hour of pulling a vacuum, my gauge only reads -29). I close both the high and low sides on my gauges and turn off the vacuum pump. I let it set for an hour. After an hour, the gauges are exactly where they were when I turned off the vacuum pump.

So then I recharge the system. To do that, I connect a can of refrigerant to my yellow gauge hose. I purge the air from that hose until refrigerant comes out. I turn on the engine, the blower, and the A/C from inside the cab. I then open up only the low side gauge.

My understanding is that refrigerant should then start entering the system and after a few minutes enough pressure builds up to kick on the compressor. Only that never happens. The compressor never kicks on.

 

What does the low pressure gauge (blue) read as you start charging? If you are charging a vacuumed out system, refrigerant should flow right in, as the can is under pressure. The pressure should rise quickly, and when it reaches the low pressure point of the pressure switch, the switch should close, and the compressor clutch should engage.

As 93celicavonv correctly stated, the pressure switch is open when pressure is low.
Is the clutch coil ok? Can be tested by applying +12vdc to the electrical connector from the car battery

 

Thanks for the reply.

As I start charging, the low side gauge goes from -29 to about 100.

Before I purchased a new compressor, I performed a test connecting a wire directly from the positive terminal on the battery to the wire coming from the compressor. It grounds through the mounting bracket, so I did not attach additional ground. The compressor did not respond. So I concluded the compressor was bad.

However, the brand new compressor behaves the same way. When I connect a wire directly from the battery to the wire on the compressor, the clutch does not respond.

 

Evaporator core. Cleaning needed?

 

Jumping in late.

When adding from via low pressure line, you should see both hi and lov at same pressure. A fully loaded system should see 70 psi when the weather is mild, and pushing 100 when hot. But one small can will not achieve normal static pressure. If pressure is balanced, then freon is flowing throughout.

Try bypassing the pressure switch. Disconnect it from the wire harness and then connect the wires in the wire harness plug together with a piece of wire. If it works, then the pressure switch is bad, or there is not enough pressure.

If pressuee switch checks out. Then disconnect the compressor coil wires from the harness. Check for voltage in the harness connector. You can then connect the coil wires directly to the battery. If the compressor comes on, then problem with amplifier, relay, fuse. If not, then compressor coil is bad.

 

Jumping in late.

When adding from via low pressure line, you should see both hi and lov at same pressure. A fully loaded system should see 70 psi when the weather is mild, and pushing 100 when hot. But one small can will not achieve normal static pressure. If pressure is balanced, then freon is flowing throughout.

Try bypassing the pressure switch. Disconnect it from the wire harness and then connect the wires in the wire harness plug together with a piece of wire. If it works, then the pressure switch is bad, or there is not enough pressure.

If pressuee switch checks out. Then disconnect the compressor coil wires from the harness. Check for voltage in the harness connector. You can then connect the coil wires directly to the battery. If the compressor comes on, then problem with amplifier, relay, fuse. If not, then compressor coil is bad.

Thanks for jumping in.

Regarding your first paragraph, temps are around 100 degrees where I live right now. I'm seeing 100-115 psi on low side and about half 0-25 on the high side.

Regarding your second paragraph, getting to the pressure sensor requires disconnecting the firewall A/C lines, removing the evaporator box from under the dash, and then you gain access to the sensor. It's not something you can jump test like it would be if it were in the engine bay. Having said that, I did remove the old pressure switch and put in a new one. Nothing changed.

Regarding your third paragraph, I've tried connecting the compressor, which is brand new, to a known good ground in the engine bay and also directly to the battery. When I do that, the compressor does nothing. The clutch does not engage. I've checked the relay and the fuse. Both are good.

Tom10 was suggesting it might be the amplifier. I've pulled it off the car but know very little about troubleshooting it. Any advice there is welcomed.

 

UPDATE: I decided to redo the test that connects the compressor directly to the battery. My previous test was done by stringing together alligator clips. I did that again and used a multimeter to discover no current was getting to the compressor.

So I found some spare wire in my garage and attached some leads to it. This time, the test worked perfectly. The old compressor still did not have clutch engagement, but the new compressor clicked on and off perfectly.

The compressor is still not working as it should with the car's system, but at least I know the compressor is not the problem.

QUESTION: I saw on a 4 Runner forum where someone who had issues with their amplifier decide to bypass it by running a wire from the A/C switch in the cabin directly to the compressor. Has anyone else tried this? Is it a viable option?

My thought was it wouldn't hurt to do as a test. If it works, I'd set up a relay and 10A fuse in the circuit for protection.

What do you guys think?

 

But your compressor was the problem, at least your old one was, per your post #31. But even your new compressor doesn't work (except when connected directly to a 12V power source)?

Does someone have the air conditioning system wiring diagram for the subject car in this forum? That would help a lot.

While my 1993 Celica electrical control for the A/C system is not like yours, the pressure switch function should be. Here is how the pressure switch on the circuit for the compressor clutch functions. If yours is similar, then the switch should be closed (continuity) at the 100-115 psi pressure you were reading. On my control, the amplifier provides power to the A/C Magnetic Clutch Relay, which is also connected to the pressure switch. In addition, there is a coolant temperature switch that has a connection into the magnetic clutch relay.

In that wiring diagram provided you in post #13, have you traced where your 12V power originates and followed it until no power is present? You may have a fuse out (which is possible given you have an old compressor whose clutch failed electronically), or you may have an A/C switch problem. You really need to follow that wiring diagram. By doing so, you will find when you have power and where it ends, and if where it ends it shouldn't, you'll identify the part that has the problem.

 

Thanks for the insight. As Tom said in post #24, it seems like I'm chasing two problems. Certainly it seems like the original compressor was bad, and until I did a better test on the new compressor last night, it seemed like it was bad too. But now I know that the new compressor is good. So now I think we've narrowed it down to one problem. That one problem is preventing the compressor from kicking on.

I'm attaching the wiring schematic for the 1984 Celica.

On the schematic, I've denoted what I've been able to verify. On the ground side, I've verified there's a good ground to the compressor. The other ground is to the A/C switch. Since it lights up when pressed, I'm concluding it has good ground. While not marked on the schematic, I believe it can be assumed the ground to the heater relay is also good since we have a good circuit up to the A/C switch (more below on that).

On the positive side of the circuit, I've bench tested the heater circuit breaker, heater relay, and 10A A/C fuse. I've not traced power along that circuit. Again, since the A/C switch lights up, I'm concluding there is continuous power from the battery all along the circuit until it reaches the A/C switch. At that point, I concluded it must be the pressure switch since as I read the schematic, it was the only thing between the A/C switch and the compressor. So I replaced the switch, but it did not solve the issue. I have not traced the wiring between the A/C switch and the pressure switch, nor have a traced the wiring between the pressure switch and the compressor.

 

If your heater blower motor works properly in all speeds, then I would agree with the the power is present at the connection to the blue (L) wire coming back from the heater relay back to the 10A A/C fuse. Your green light comes on when you push the A/C switch to ON, but have you verified the power is 12VDC? The lamp may light with a lower voltage. Also, have you verified the Y-L (yellow wire with blue stripe) leaving the A/C switch to have 12VDC? If that checks out, with your pressure switch in the A/C refrigerant system that you verified has 100-115 psi in it, have you verified there is 12VDC on both wires at the pressure switch? If both the Y-L (yellow wire with blue stripe) and the L-O (blue wire with orange stripe) have 12VDC, then what voltage is at the connector for the compressor - is it 12VDC? Or is it zero? If zero, you have an open in the wiring between the pressure switch and the compressor (if all the other tests were good). Does your condenser fan motor work when the A/C is turned on?