95 Firebird a/c battle(question)

[95Firebird12345678]

Hello, I’m troubleshooting my ac on a 95 firebird v8.

The ac pump will not engage unless jumper'd.
I can put a jumper in the fuse box where the relay sits to activate the pump and the ac works.
I’ve tested the relay to make sure it is working, it is. I switched the relay out with a known good one just to test that the other one is working.

I think my freon pressure is 45 low side/150 high side when jumper’d (ac running).
That’s a little over 2 cans, it takes a little less than 3 cans to be full.
It should be running with that amount. Unless I’m wrong.

I’ve tested the pressure switch and replaced it just to be safe.
I have jumper’d the harness to the pressure switch going back to the PCM, gray to red (nothing) and red to black(nothing). I think the fan kicked on when I crossed the gray and red wires. I did this a couple of times but I’m not confident that is what caused the fan to kick on. Don’t cross the gray and black.

There is suppose to be another pressure switch somewhere. ???
I have followed the lines and cannot find another pressure switch anywhere. Nothing on the pump just 2 wires for power and ground.
Where is the 2nd pressure switch suppose to be located?
Any suggestions would be helpful.

Note: I’ve changed out the Expansion valve, Accumulator and the Pressure switch between the expansion valve and the accumulator. Everything I’m reading says this is the low pressure switch but it looks like it is on the high pressure side to me. Anybody know which switch that really is?

Thanks

[Blue Bowtie]

Some systems used a high-pressure cutout switch built into the rear of the compressor.

Some systems used an refrigerant pressure sensor (red-black/black/gray wires) in addition to cutout switches.

Some systems used an evaporator temperature sensor (dark blue/black/gray wires).

A pressure switch after the expansion valve/orifice would be the low pressure switch.

What are the system pressures with the A/C compressor shut off?

What is the engine coolant temperature? A high CTS input can prevent the PCM from turning on the A/C compressor.

[Blue Bowtie]

This may help:

[95Firebird12345678]

QUOTE=Blue Bowtie;7229050]Some systems used a high-pressure cutout switch built into the rear of the compressor.
A:
I cannot find a wired/connector cutout switch on the pump.
I will look again just to make sure I did not miss it.

Some systems used an refrigerant pressure sensor (red-black/black/gray wires) in addition to cutout switches.
A:
OK, I think this is the one that I have tested above. It has the red-black/black/gray wires
It looks like it is on the high pressure side between the accumulator and expansion valve.

Some systems used an evaporator temperature sensor (dark blue/black/gray wires).
A:
I don't see this one anywhere.
Let me look some more.

A pressure switch after the expansion valve/orifice would be the low pressure switch.
A:
Ok, I think this is the one I am having a problem finding.
There is nothing on the low pressure line(larger line) from the expansion valve to the pump except the test/fill port.
You’re not talking about the sensor with the red-black/black/gray wires, correct?

What are the system pressures with the A/C compressor shut off?
A:
1) car off/ ac off: if it sits for a few days basically 100 on both sides.
I just walked out and took a pressure reading: low 90-93 / high 95-97 (I worked on it yesterday)
(i loose a little pressure every time I hook up the gauge, even when I unhook and keep the gauge pressurized)
2) car on / ac on/ fans on: low 45 / high 150 (these number are what I wrote down last week before I posted this question)
3) car on / ac off: low 75 / high 150 (these number are what I wrote down last week before I posted this question)

What is the engine coolant temperature? A high CTS input can prevent the PCM from turning on the A/C compressor.[/quote]
A:
The temp rarely goes to 210, only if I’m sitting in traffic on a hot day
It usually sits at 160 t0 180, she has a 160 thermostat.


I’ve tried to answer these clearly.
Thank for questions and answers.

Visual Note about my expansion valve and lines:
So from the accumulator (small high pressure line)—>
—pressure switch (with the red-black/black/gray wires) —>
—going into the lower port of the expansion valve at the firewall (small high pressure line)

Coming out of the upper port expansion valve is the larger line (low-pressure line)—>
—passes the low pressure port (low-pressure line)—>
—directly to the pump

[95Firebird12345678]

[quote=Blue Bowtie;7229051]This may help:

Yes, thank you

[Blue Bowtie]

It may help to scan the PCM for stored error codes. This is a bit more of a challenge on a 1994-95 PCM, since they are not quite OBD-II compliant, but also do not operate like the eartlier ECMs. I GM Tech-II or SnapOn Modis/brick is usually required.

[95Firebird12345678]

Originally Posted by Blue Bowtie

It may help to scan the PCM for stored error codes. This is a bit more of a challenge on a 1994-95 PCM, since they are not quite OBD-II compliant, but also do not operate like the eartlier ECMs. I GM Tech-II or SnapOn Modis/brick is usually required.

I don't have either one.
I will check and see if someone I know has one or autozone maybe.

Thanks

[brcidd]

Unhook battery for 10 seconds to reset any a/c codes- that model/yr counts rapid compressor cycles (low charge) and sets codes readily.

[95Firebird12345678]

Originally Posted by brcidd

Unhook battery for 10 seconds to reset any a/c codes- that model/yr counts rapid compressor cycles (low charge) and sets codes readily.

Thank You.
I think that worked.
I tried it last night. She was pushing 50º F out of the ac. (90ºF outside)
I'm going to check it again tonight, make sure it wasn't a fluke. Add a little more freon if it needs it.

[95Firebird12345678]

Ok, that worked. I added a little more freon today.
Hopefully she is good for now.
I still want to find that other switch location.
Thank you Blue Bowtie and brcidd