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 No AC after opti replacement

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bigredwagon

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PostSubject: No AC after opti replacement    Tue Jul 18, 2017 3:44 pm

So after replacing the opti and some other parts while in there the ac no longer works. Nor does the secondary fan come on with ac turned on.
Everything worked before the opti work and none of the ac components were touched aside from the temp sensor on water pump. All fuses and connections look good. Pulled the sensor on the water pump and the secondary fan does work. Tried pulling the battery to reset the system multiple times but there's no change. The refrigerant level seems alright based on the cheapo gauge I have but the compressor isn't running so the true reading is unknown.
The ac clutch spins freely but doesn't seem to be engaging. Tried jumping the connection at the accumulator but nothing seems to change with that either.

Are the clutch and the secondary fan wired together? What makes the clutch engage? What's going on here?
At 90°+ in the shade this car is undrivable unless you want to arrive at your destination angry and wet.
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bigredwagon

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PostSubject: Re: No AC after opti replacement    Thu Sep 14, 2017 1:43 pm


Weather is changing and the defrost struggles to clear the windshield with working ac. Uncomfortable is turning into unsafe.
Thoughts?
Anybody know what signals the clutch to engage? Or what is stopping it?
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silverfox103
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PostSubject: Re: No AC after opti replacement    Thu Sep 14, 2017 1:52 pm

You may be just low on freon, your wagon has the symptoms. Also the temp sender on the water pump, are cheap enough, I probably would replace that also.

Tom
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bigredwagon

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PostSubject: Re: No AC after opti replacement    Sun Sep 17, 2017 10:36 pm

The temp sensor was replaced last summer. I'll have to check the Freon again. What pressure are these systems supposed to have in them? If I understand correctly the pressure being either too high or low will stop the system from working.
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lamune

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PostSubject: Re: No AC after opti replacement    Mon Sep 18, 2017 1:23 am

The proper operating pressure varies based on temperature and humidity. My system has a leaky compressor so I have to fill it all the time, and pretty much all I do now is make the low side 32PSI while the compressor is running and it seems happy there until it leaks out over the course of a couple of months.

If you have access to the service manual there's some tables in there for more precise evaluation.

Also the old rule of thumb seems to work well with the system in these cars- if your temp of the two lines coming out of the firewall is about the same, you're probably ok.
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Fred Kiehl

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PostSubject: Re: No AC after opti replacement    Tue Sep 19, 2017 10:24 am

There should be a high pressure switch on the compressor. It acts like the one on the accumulator, but measures high (over) pressure. The signal for AC comes from the control panel, goes through the accumulator switch, and the compressor switch. The circuit operates the compressor clutch. There is also a line that goes to the computer, telling it when the control panel is asking for AC. That will turn on the fan as well.
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bigredwagon

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PostSubject: Re: No AC after opti replacement    Fri Sep 22, 2017 1:01 pm

Well 'ol red does not appear to be losing any refrigerant. Tried going too high and then too low with the pressure to evoke some change but no luck. Rechecked the electric fan, fuses and connections. Everything seems to work.

If I shove some metal in the plug going into the low pressure sensor to jump it. It acts like it does with the ac on.. There is a slight audible change like the compressor is getting the green light but the clutch is still not engaging. Makes me think the low pressure switch is working. Maybe the high side sensor is faulty??
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Fred Kiehl

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PostSubject: Re: No AC after opti replacement    Fri Sep 22, 2017 1:23 pm

You could have a bad clutch as well. Check for power at the clutch connector.
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bigredwagon

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PostSubject: Re: No AC after opti replacement    Tue Oct 17, 2017 9:07 pm

How do I go about checking that? Reluctantly I recently bought a multimeter. Electrical isn't my favorite so I'd borrow one if absolutely necessary.
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Fred Kiehl

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PostSubject: Re: No AC after opti replacement    Tue Oct 17, 2017 9:42 pm

You need to check the clutch continuity (ohms), check if it has battery voltage at one side of the connector (DC volts 20?), and ground at the other side of the connector (ohms to the frame or battery - terminal). It will only have voltage at the connector when the AC is on, and the high and/or low pressure switches are closed. The low switch is on the accumulator, and the high switch, if you have one, is on the compressor.
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