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94 CS AC Questions


Leadfoot
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Bit of a long story.

Noticed in June as it really starts heating up here in TX that the AC wasn't cooling as much as it should be.  Wife was due with out first child in early July so I was a bit preoccupied.  I did hook gauges up and find it was low on freon.  Went to add some freon towards the end of July.  That went fine except the high side valve would not shut completely when finished and removing gauges. (seen this before so not shocked, just irritated).  All freon leaked out.  Decided to order new high side/Low side ports, orings, and dryer.  Replaced those and vacuumed the system down.  Went to add freon.  Did not notice until halfway into this that the compressor was not running.  Finished charging and the compressor still doesn't cycle on.  Was busy with the baby so another week or so went by.  Had a chance to look at it and everything seemed fine, but no compressor cycling.  I removed the relay and put power to cycle the compressor and it does run, but the air still isn't getting cold.  I guess it's possible something is still leaking and the freon leaked out.  However, It seems there is still something wrong keeping the compressor from cycling.  I am trying to rack my brain for what could be causing that.  I am in a bit of a fog with a newborn and feel like I might be missing the obvious.  Anyone else encountered this?  

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You can't fill the system all too well without the compressor kicking on.

If the compressor is not kicking on with the low side above 50 psi and high side below 400 psi, then something is off. You can bypass the low pressure and high pressure switches momentarily to see if that engages the compressor. Also, check the relay itself. They're not invincible.

I have a feeling you did not fill the system enough or the freon leaked out again, causing your compressor to not kick on due to low pressure.

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I'm on board with bypassing the low switch momentarily to test the theory that it may be bad, the price of a new switch needs to be weighed against the value of the Freon lost in the experiment though.

It may be more cost effective to replace it or extract it and test it with an air compressor with a little ghetto test fixture made of crap tthat's laying around. 

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4 hours ago, Leadfoot said:

I removed the relay and put power to cycle the compressor and it does run, but the air still isn't getting cold.  I guess it's possible something is still leaking and the freon leaked out. 

What are the gauge pressures when you force the compressor to run?  That's how you'd know if the system is still too low on refrigerant to run normally.

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22 hours ago, Imp558 said:

I'm on board with bypassing the low switch momentarily to test the theory that it may be bad, the price of a new switch needs to be weighed against the value of the Freon lost in the experiment though.

It may be more cost effective to replace it or extract it and test it with an air compressor with a little ghetto test fixture made of crap tthat's laying around. 

 

22 hours ago, vipmiller803 said:

You can't fill the system all too well without the compressor kicking on.

If the compressor is not kicking on with the low side above 50 psi and high side below 400 psi, then something is off. You can bypass the low pressure and high pressure switches momentarily to see if that engages the compressor. Also, check the relay itself. They're not invincible.

I have a feeling you did not fill the system enough or the freon leaked out again, causing your compressor to not kick on due to low pressure.

Ok, other than jumping the relay, how would I test the swtich?

 

20 hours ago, Schurkey said:

What are the gauge pressures when you force the compressor to run?  That's how you'd know if the system is still too low on refrigerant to run normally.

I need to hook them up and check.  I only had about 20 minutes before I knew my daughter would be waking up so I just ran out and jumped the relay to see if it kicked on and if the air got cold.  

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Don't jump the switch,  we misinformed you. That one has an actual sensor. 

I have to dig through Alldata and draw a diagram for Mitchell tonight,  I'll dig around in the Cutlass prints and put together a diagnostic ritual for you. 

You're going to need a multimeter with resistance and DC volts though.

20180829_121343.jpg

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Ah thank you Tom for looking that up. I'm used to the simple two wire in line switches on mine. Hmm might need to actually test the sensor. If there's a resistance the pcm is looking for, you could use a resistor on the correct pins to fool it temporarily. I'm no help there though, as I do not know the correct resistance or the pinout of the connector.

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On 8/29/2018 at 11:21 AM, Imp558 said:

Don't jump the switch,  we misinformed you. That one has an actual sensor. 

I have to dig through Alldata and draw a diagram for Mitchell tonight,  I'll dig around in the Cutlass prints and put together a diagnostic ritual for you. 

You're going to need a multimeter with resistance and DC volts though.

20180829_121343.jpg

I have several multimeters so I am good there.  

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I see a few things you can test here. Jumping pin 30 to 87 on the relay socket will engage the clutch, if it doesn't the clutch, fuse, clutch ground, or wire to the clutch is the problem. 

Also you can slide a sewing pin alongside the red/black wire on the pressure sensor and read the voltage, it's 0-5v so if you know how many pounds of refrigerant you put in it shouldn't be hard to figure out the scale of the voltage.

And make sure the car has no codes.

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  • 1 month later...

I jumped the relay and the compressor engaged.  No cold air.  I tried using the needle across the green and black wires coming from the compressor (didn't see red/black) and got 0v.  When looking on Rockauto I see 2 switches listed.  Is there a simple way to figure out which one I have?

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If you got the compressor going and still have no cold air then the system either has a blockage, no or low charge, or a serious lack of heat exchange. Your switches are likely functioning just fine. Don't go ordering stuff blindly.

Hook up the manifold gauges with the compressor forced on and report pressures.

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