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Discussion Starter #1
AC worked fine all summer. Has worked fine for 3-4 summers. It worked fine today. Drove somewhere, parked...shut the car off then remembered I didn't turn off the AC so I switched the knob to the off position with the car off. I don't like starting the car with the AC on. Went in to the BBQ, came out tonight and started the car and turned on the AC and nothing. The compressor doesn't come on.

I had a problem last year with the fan relay's popping due to old/worn out fans. I replaced the fans and the relay(s) and haven't had a problem since. I don't remember exactly but I'm pretty sure the AC did work even with a burned out fan relay. Just the car would overheat very fast in traffic.

So, it's gonna be in the 90's again this week and my mechanic is closed for vacation so I'm hoping it could be a fuse or relay or something I can fix easily by myself. I've had a catastrophic failure of the compressor before and the instant discharge of refrigerant was quite dramatic. That definitely did not happen. Though I'm afraid the headers might have finally burned a pinhole in the ac lines and the system just slowly discharged while parked today. AC lines are bent away from the headers for clearance and wrapped in that heat wrap material. But still that seems the most obvious problem.
 

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Just a quickie. I would think the first thing to check would be, is the clutch engaging? I'm just learning about the AC. I would get one of those cans with the valve installed @ the parts store and hook it up if it is coming on. Then maybe you could find out if you have a leak. I'm sure more answers will follow. Until you find out for sure. Stay cool.


Mark: Snowman-33
 

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Discussion Starter #3
No the clutch doesn't engage and so the compressor doesn't come on.

I kind of remember reading about a way to force it to engage for testing? Idk..
 

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Hello TGO, Yes there is electrical that will keep a charged system from working and compressor from engaging.In the underhood elect center......Check the A/C compressor relay and the fuse(#7) that feeds it.


Jim
 

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Discussion Starter #6
I was just out there looking at the relay(s). They look fine to me. What that means is I don't see any "heat" on them. When my fans were bad the relay basically melted. The prongs turned blue-ish, etc. I don't see any of that. I didn't check the fuse though I'll have to do that.

I also pulled the temp sensor with the car running and both my fans came on.

I felt around the ac lines where they go under the header. I don't feel any oil on the lines themselves. They feel and look dry. I'm not sure if the header heat wrap that's around them would absorb all that would have leaked out. Still my gut is telling me that that's the problem. I suppose all the refrigerant wouldn't have to leak out, just enough to get a low pressure reading and stop the compressor from working.
 

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On the side of the Receiver/Drier there is a pressure switch. When the Freon gets low, this switch prevents the compressor clutch from engaging.

Simple test: unplug the harness and use a piece of wire and jump across the slots in the plug. This is just temporary to see if the relay and clutch works. You will need to have the engine running with the A/C set to on.
When you jump across the slots in the plug, the compressor should engage. If the clutch engages, then either the Freon level is low or the pressure switch is bad.

My pressure switch failed a few years ago. The switch is easy to replace as the switch just unscrews.

Later,
Michael
 

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Discussion Starter #8
I believe the pressure switch is new-ish. When I first got the car it was november 2012...no need for AC then but the following summer I had the system serviced. I tried charging it myself which worked for a little while but there were multiple leaks. I took it to a shop and they replaced the compressor and they said there was a leak at the pressure switch so they changed that as well.

IDK the quality of the part they put in there...I suppose it's entirely possible that it failed.

If I jump the switch and the compressor comes on...will the AC blow cold is there is low pressure? Is there any other way to tell if the pressure is low other than putting gauges on it? It's really hard to believe the car was blowing ice cold when I drove it and only a few hours later the AC doesn't work at all.

Also, fuse #7 is for the primary cooling fan so since both fans work the fuse is ok.
 

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If you jump across the plug and the compressor comes on, the AIR may or may not blow cold depending how low the system may be.

My pressure switch was also leaking, so I replaced the o-ring and no more leak.

The gauges are fairly inexpensive from local parts stores.

As your car is a 1995, you have R134a Freon which is still available without a license and fairly reasonable in price. My local Sam's club was selling cases of 12 cans for $30. I purchase 6 cases to have around for future use.

Later,
Michael
 

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In the above post that contains a service manual photo, the switch that is under the pencil is the one on the side of the Drier.
The switch is labeled "A/C Compressor Pressure cycling switch."

I have the 1995 Service manual and the diagram is the same for the 1996.

Please also check the under-hood electrical center to ensure that the connectors for the A/C Compressor relay are not melted. Also check the connector on the compressor. On my Taurus SHO, the clutch connector melted and I had to replace.

Here are scans of the service manual for clutch diagnosis.
 

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And another page.
 

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Discussion Starter #13
I had gauges but I think I threw them out. I have to look. Either way it looks like I have to take it in since the system will need to be evacuated and recharged. Probably time to change the dryer and orifice tube since they are original too.
 

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TGO,
You know you're way around your car and I do understand wanting it taken care of. O'Reilly also loans out vacuum pumps. If it did leak then that and the guages will let you know. Just trying to save some DOH! Good luck Bud.

Mark: Snowman-33
 

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All the above information is great, but did you systematically check for voltage at each stage of the wiring, starting with the fuse? There are three ways to trouble shoot: start at the compressor, start at the fuse, and just jump in anywhere and make a guess. The first two are going to find the problem, and the third will cause frustration, and cost you a lot of money and time.

I would get my VOM out, and check for voltage at the clutch (ignition on engine off AC on). If it has voltage, it is either the clutch, or probably low refrigerant. If it does not have voltage, check the next connector upstream until you find voltage. Depending on the appearance of voltage, it can tell you what the issue is. If you have voltage above the sensor on the accumulator, the refrigerant is probably low. If you have voltage above the relay, the relay is bad. If you have voltage above the fuse, the fuse is bad. The AC module in the interior switch is also in the circuit. I had a module go bad on my OCC, and did not get a "request signal" from the unit. I believe the request signal actuates the relay. You do not necessarily have to check everything, because when you find the voltage, it tells you what the problem is.

The car is designed to start with the AC on, and starting it with the AC off, then turning it on makes no difference to the car. It is a nice thought, but irrelevant act.
 

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Before you open the system, follow the flow chart for diagnosis of the clutch. The steps will get you to the problem before you just start throwing parts that may be good.

The flow chart mentions a TECH II, but that is not necessary of you have a cable and a laptop with Scan9495/Freescan/Datamaster etc.

Let me know if you need additional pages from the service manual.

Michael
 

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Discussion Starter #17
I may go borrow the gauges just to see but even still...if it turns out to be anything but the actual switch in the cabin I still have to take the car somewhere to have the system evacuated and refilled.

Can't change the pressure switch without discharging the system right?

Even if it's just the clutch and doesn't require opening the system, it's still a major PITA and I don't have the tools required to do the job.

The fuses are good. I know that because both fans work. The relay doesn't appear burned. I can replace it just to see if it helps but I think the gauges will tell me more for free.

I'm thinking the headers just burned a pinhole in the ac line, which seems to be a chronic problem for people with the CIA Gen 2 Tri Y. And it's happened to me before.
 

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If the system has leaked out all the R134. Why would you have to evacuate the system? Get the gauges and vacuum pump from them. Repair, replace, recharge=refrigeration.

Mark: Snowman-33
 

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Discussion Starter #19
I didn't know they loaned out vacuum pumps too.

I tend to pick my battles. Are the bolts for the lines on the back of the compressor easy to get to? Can you reach everything from the top or do you need to get under the car? I don't want to be laying in the street on the hot pavement in 95 degree weather sweating and cursing and busting my knuckles. I'm not rich but I've moved beyond needing to do that at this point in my life lol!
 

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TGO
Not all of the stores loan out the vacuum pump. But it would seem if they have the guages then too they should have the pump. I would check to see if you have any pressure in the system and check what was suggested above. I understand having it done but there is some satisfaction in doing it yourself too. Before I retired I would have things done. Now I'm learning more. Recent differential thread might cause me to learn how to set up gears. Thanks Fred. BTW, In my nearsightedness I missed that your compressor wasn't coming on in the first post. My Bad. You should find & fix the problem about the first snow. Good Luck

Mark: Snowman-33
 
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