Cold one day HOT the next (AC)
06-23-2007, 09:52 PM
#1
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Thread Starter
Cold one day HOT the next (AC)
Well, I had the AC topped off with R-12 a couple months back and it's been the coldest since I bought her; Until yesterday that is 
I kinda felt a difference in cooling night before last, but yesterday day I got nothing but hot air! The AC switch still works and I hear the compressor switching on. I think I may have sprung a leak somewhere?
Now that we're well into the tripple digits here in Vegas, I need to act fast
!
Looks like I'll start with the dye and hope to find a fitting loose...Anyone have any other advice on where to look for problematic areas?
I kinda felt a difference in cooling night before last, but yesterday day I got nothing but hot air! The AC switch still works and I hear the compressor switching on. I think I may have sprung a leak somewhere?Now that we're well into the tripple digits here in Vegas, I need to act fast
!Looks like I'll start with the dye and hope to find a fitting loose...Anyone have any other advice on where to look for problematic areas?
06-23-2007, 10:00 PM
#2
Race Director
Darien
Do you have a sniffer.......thats an easy way to track down a leak too? I'd start with all the joints that have O rings in them....the worst place to have a big leak is the evaporator.....since you have to pull the dash to get to it....but those tend to be small leaks.....
Odd that you went from good a/c to nothing.....it does sound like the low pressure switch working..but you said the compressor is engaging....so that can't be it....but the compressor shouldn't engage if its low on freon? unless you bypassed it?
Do you have a sniffer.......thats an easy way to track down a leak too? I'd start with all the joints that have O rings in them....the worst place to have a big leak is the evaporator.....since you have to pull the dash to get to it....but those tend to be small leaks.....
Odd that you went from good a/c to nothing.....it does sound like the low pressure switch working..but you said the compressor is engaging....so that can't be it....but the compressor shouldn't engage if its low on freon? unless you bypassed it?
06-23-2007, 10:04 PM
#3
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Thread Starter
Thanks Brian, will do!
I can't see any movement of fluids in the sight glass, and as for the compressor, I'm not sure if it's engaging, but I can feel the extra power drawl.
I can't see any movement of fluids in the sight glass, and as for the compressor, I'm not sure if it's engaging, but I can feel the extra power drawl.
Originally Posted by IcemanG17
Darien
Do you have a sniffer.......thats an easy way to track down a leak too? I'd start with all the joints that have O rings in them....the worst place to have a big leak is the evaporator.....since you have to pull the dash to get to it....but those tend to be small leaks.....
Odd that you went from good a/c to nothing.....it does sound like the low pressure switch working..but you said the compressor is engaging....so that can't be it....but the compressor shouldn't engage if its low on freon? unless you bypassed it?
Do you have a sniffer.......thats an easy way to track down a leak too? I'd start with all the joints that have O rings in them....the worst place to have a big leak is the evaporator.....since you have to pull the dash to get to it....but those tend to be small leaks.....
Odd that you went from good a/c to nothing.....it does sound like the low pressure switch working..but you said the compressor is engaging....so that can't be it....but the compressor shouldn't engage if its low on freon? unless you bypassed it?
06-23-2007, 11:19 PM
#4
Rennlist Member
You can visibly see if the compressor clutch engages....or doesn't as the case may be. That's probably one of the first things to check. If it isn't, you can then bypass the pressure switch to see if it engages. If it does, you'll most likely have a low pressure situation.
06-24-2007, 06:45 PM
#5
Chronic Tool Dropper
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The cooling fans "engage" when you push the AC button if there's even minimum pressure in the system. My instant guess is that the compressor isn't turning. Might be low freon, mich be something else. Start off with a look at the compressor to see if it really is not turning. If it is turning but there's no cold, You probably have a vacuum problem like a cracked/split actuator boot someplace. There's a lot more diagnostics to do if the compressor is not turning.
Post what you find!
Post what you find!
06-24-2007, 09:58 PM
#7
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Thread Starter
Compressor is NOT turning! How do I bypass the "pressure switch"?
Originally Posted by Ed Hughes
You can visibly see if the compressor clutch engages....or doesn't as the case may be. That's probably one of the first things to check. If it isn't, you can then bypass the pressure switch to see if it engages. If it does, you'll most likely have a low pressure situation.
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06-25-2007, 03:33 AM
#8
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Thread Starter
With the compressor not turning and the heater valve working as advertised, where should I look next?
Originally Posted by dr bob
The cooling fans "engage" when you push the AC button if there's even minimum pressure in the system. My instant guess is that the compressor isn't turning. Might be low freon, mich be something else. Start off with a look at the compressor to see if it really is not turning. If it is turning but there's no cold, You probably have a vacuum problem like a cracked/split actuator boot someplace. There's a lot more diagnostics to do if the compressor is not turning.
Post what you find!
Post what you find!
06-25-2007, 04:18 AM
#9
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Darien, one of the most dangerous things for an AC compressor is to operate without oil. Just like an engine. Now, we change our engine oil on a regular basis, since it sees combustion and as such accumulates contaminates. AC oil does not...but where does it get its lubrication? From the gas.
This is why I turn the a/c on on ALL of my cars for the first few minutes after I start the car, regardless of outside air temperature. Even if it is an incredibly cold winter night in Fort Lauderdale, perhaps only 65 degrees...I turn on the AC along with the heat, just for 1 minute, to get the lubricant into the compressor.
-Recently, one of my cars, a Jetta GLX, developed an AC problem. I turned on the AC and nothing happened- the compressor wouldn't come on because the gas pressure was too low. I took it to a shop and they used one of these ultraviolet pen lights to tell me that the compressor was leaking and needed to be replaced. Great. Well, this is my work car in Memphis, and I fly nights, so I really don't need A/C, since the only time I'm going to be wearing clothes that I'd not want to sweat in will occur at night when it is cool anyway. But the shop owner and me both had the same reaction: Add gas and stop-leak. And that is just what I did- suddenly the AC came back to life. Today, I took two colleagues running at this place called Shelby Farms to go running, and on the way back...the AC was so cold I had to turn it off.
N!
This is why I turn the a/c on on ALL of my cars for the first few minutes after I start the car, regardless of outside air temperature. Even if it is an incredibly cold winter night in Fort Lauderdale, perhaps only 65 degrees...I turn on the AC along with the heat, just for 1 minute, to get the lubricant into the compressor.
-Recently, one of my cars, a Jetta GLX, developed an AC problem. I turned on the AC and nothing happened- the compressor wouldn't come on because the gas pressure was too low. I took it to a shop and they used one of these ultraviolet pen lights to tell me that the compressor was leaking and needed to be replaced. Great. Well, this is my work car in Memphis, and I fly nights, so I really don't need A/C, since the only time I'm going to be wearing clothes that I'd not want to sweat in will occur at night when it is cool anyway. But the shop owner and me both had the same reaction: Add gas and stop-leak. And that is just what I did- suddenly the AC came back to life. Today, I took two colleagues running at this place called Shelby Farms to go running, and on the way back...the AC was so cold I had to turn it off.
N!
06-25-2007, 01:26 PM
#10
Chronic Tool Dropper
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Darien--
Look on the receiver-dryer in front of the condenser. There are two devices mounted to the plumbing there. On top there's the pressure transducer for the fans-n-flaps. it has the screw terminals on it. Underneath that on the same piping is the pressure switch, with a single two-wire connector stuck on to it. Pull the connector, and then test the switch itself with no wires attached. Use your ohm meter to see if there's continuity through the switch. If there is continuity (resistance close to zero ohms) you can plan a liittle electrical sleuthing. If the switch is open (very high resistance or infinite ohms) you've probably leaked out your freon again. Basic testing this way avoids running the compressor with no freon or oil circulating and eliminates the risk of inadvertent damage. Plus, you can work on it in your air-conditioned garage without having the door open or the car running.
Look on the receiver-dryer in front of the condenser. There are two devices mounted to the plumbing there. On top there's the pressure transducer for the fans-n-flaps. it has the screw terminals on it. Underneath that on the same piping is the pressure switch, with a single two-wire connector stuck on to it. Pull the connector, and then test the switch itself with no wires attached. Use your ohm meter to see if there's continuity through the switch. If there is continuity (resistance close to zero ohms) you can plan a liittle electrical sleuthing. If the switch is open (very high resistance or infinite ohms) you've probably leaked out your freon again. Basic testing this way avoids running the compressor with no freon or oil circulating and eliminates the risk of inadvertent damage. Plus, you can work on it in your air-conditioned garage without having the door open or the car running.
06-25-2007, 03:32 PM
#11
Race Director
Originally Posted by dr bob
Darien--
Look on the receiver-dryer in front of the condenser. There are two devices mounted to the plumbing there. On top there's the pressure transducer for the fans-n-flaps. it has the screw terminals on it. Underneath that on the same piping is the pressure switch, with a single two-wire connector stuck on to it. Pull the connector, and then test the switch itself with no wires attached. Use your ohm meter to see if there's continuity through the switch. If there is continuity (resistance close to zero ohms) you can plan a liittle electrical sleuthing. If the switch is open (very high resistance or infinite ohms) you've probably leaked out your freon again. Basic testing this way avoids running the compressor with no freon or oil circulating and eliminates the risk of inadvertent damage. Plus, you can work on it in your air-conditioned garage without having the door open or the car running.
Look on the receiver-dryer in front of the condenser. There are two devices mounted to the plumbing there. On top there's the pressure transducer for the fans-n-flaps. it has the screw terminals on it. Underneath that on the same piping is the pressure switch, with a single two-wire connector stuck on to it. Pull the connector, and then test the switch itself with no wires attached. Use your ohm meter to see if there's continuity through the switch. If there is continuity (resistance close to zero ohms) you can plan a liittle electrical sleuthing. If the switch is open (very high resistance or infinite ohms) you've probably leaked out your freon again. Basic testing this way avoids running the compressor with no freon or oil circulating and eliminates the risk of inadvertent damage. Plus, you can work on it in your air-conditioned garage without having the door open or the car running.
This is a great idea.....typically when Bill & I diagnose a non op a/c we start by jumpering the lower pressure switch (on the bottom) that Bob talked about and the freeze switch (by the expansion valve near the main air distribution housing)....if the compressor still doesn't turn.....we rig a wire from the 12V jump start post and try to turn on the compressor that way......"If" that starts the compressor and the pressure #'s are normal indicating a normal charge then its likely the relay in the control head is bad....but thats an easy fix too....However Bobs comment on measuring the resistance of the low pressure switch to determine the freon level without running anything is an excellent idea & you should do that first!
06-25-2007, 03:51 PM
#12
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Thread Starter
Thanks Bob/ Brian,
I'll try that next...
For gee wiz, I checked the compressor freeplay and I can turn it by hand. I also visually checked the wiring to the pressure switch for any flaws; one of the wires had chaffed thorugh the protective cover so I cut both wires and spliced new connectos on. Still no worky, so I checked for pressure on low and high servicing ports. I just used a screw driver to lightly depress the valve stems, they both had VERY little pressure. Could that be an idication of freon low?
More to follow as I get new input for t-shooting
Thanks again
I'll try that next...
For gee wiz, I checked the compressor freeplay and I can turn it by hand. I also visually checked the wiring to the pressure switch for any flaws; one of the wires had chaffed thorugh the protective cover so I cut both wires and spliced new connectos on. Still no worky, so I checked for pressure on low and high servicing ports. I just used a screw driver to lightly depress the valve stems, they both had VERY little pressure. Could that be an idication of freon low?
More to follow as I get new input for t-shooting
Thanks again
06-25-2007, 04:12 PM
#13
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Thread Starter
Well, my multi-meter is out, so jumpered the wires to the pressure switch with AC switch on for less than a second and the compressor came to life.
I know I probably have more wires to check, but for now I'm leaning towards a freon leak. Atleast the compressor shows signs of life
I know I probably have more wires to check, but for now I'm leaning towards a freon leak. Atleast the compressor shows signs of life
06-25-2007, 06:28 PM
#15
Race Director
Darien
Okay that sounds like a low charge tripping the low pressure switch DO NOT RUN THE COMPRESSOR anymore until you refill with freon and OIL.....time to start looking for a leak!
Okay that sounds like a low charge tripping the low pressure switch DO NOT RUN THE COMPRESSOR anymore until you refill with freon and OIL.....time to start looking for a leak!