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Installed my A/C, compressor not kicking on???
#351404
06/18/09 11:54 PM
06/18/09 11:54 PM
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Joined: Nov 2004
Posts: 227
Scottsdale, AZ
Cudalord
OP
enthusiast
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OP
enthusiast
Joined: Nov 2004
Posts: 227
Scottsdale, AZ
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I just installed a classic auto air system on my 70 Cuda. Pretty smooth installation, everything hooked up fine with a little tweak here and there.
I took the car to a shop today to have them evac/charge the system. He hooked up this digital machine to the car and ran the evac for about 45 minutes and said the car took about 2.5 lbs of freon. The a/c was working as we were sitting there in the garage bay, and for about an hour after driving around town.
When I got home, parked the car for about 2 hours, came back to test it, and no more cold a/c:(. I popped the hood and noticed the clutch wasn't engaging. Thinking it was low on freon, I put my a/c pressure gauge up to the low pressure line and it showed in the "red", meaning over-charged...???
Not sure what to do from here. I'm going to take it back to the shop tomorrow, but honestly, A/C systems have never been my strength. Any idea why the clutch isn't kicking in? Is the high reading on the gauge for real, or is it just my generic AutoZone gauge giving me a false reading?
Thanks in advance!
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Re: Installed my A/C, compressor not kicking on???
[Re: Cudalord]
#351405
06/19/09 01:18 AM
06/19/09 01:18 AM
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Anonymous
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Anonymous
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PRESSURE gauges (A/C manifold) DO NOT TELL YOU anything about the charge whether in operation or not, unless it's severly undercharged, IE so low on pressure that it's obvious on high/ low side, or so severly overcharged that the high side is off the map.
You may have a leak and indeed may now be undercharged---most units have a low pressure switch that will cut off the clutch on low pressure so that the system (compressor) isn't damaged.
You may have a wire connection/ switch/ other electrical component failure
One quick check you can do is to "hot" wire the clutch (make sure the blower is on) for a SHORT run to tell if you still have cooling. IF you do, it's probably an electrical problem, may even be the low press switch itself
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Re: Installed my A/C, compressor not kicking on???
[Re: Cudalord]
#351408
06/19/09 10:43 AM
06/19/09 10:43 AM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
I ran a "hot wire" to the compressor. Didn't want to keep it going just in case the system was low (from my understanding this could cause damage to the compressor). Anyway, the compressor engaged immediately once I jumped it with the hot wire.
Can't imagine the switch would be bad, but who knows, weirder things have happened. I will have them check the charge on the system then take it from there.
I did do a leak check this morning with my "blue light". Not a single obvious leak anywhere. And, they guy who was charging it said he did a pressure/leak test, and saw no faults.
Any other suggestions? Kind of dissapointment after doing all that work getting it installed, but I know we'll figure it out...
I'll bet you it's over charged, I had the same problem and pulled 2.65# out of mine and put 1.8 back in and it works great. I have a AC machine. I had 2.0# in my other car and it works better too with 1.8#, that's been my experience on two cars that I installed sanden compressors on. 
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Re: Installed my A/C, compressor not kicking on???
[Re: Challenger 1]
#351409
06/19/09 11:19 AM
06/19/09 11:19 AM
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Anonymous
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Anonymous
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Would overcharge kick the compressor out? Do these systems have a high pressure limit?
Now that you know the system cools with the clutch jumpered, should be simpler to troubleshoot where you are losing power.
BEST way to check charge is by combination of high side pressure versus temp and compressor superheat. I'm not familiar with the new refrigerants, but with R12 I used to MAKE SURE that the compressor superheat was AT LEAST 15*F. Lower superheat means the compressor is starting to see liquid in the suction. Too high (warmer suction) superheat means the undercharge, and the compressor is not getting cooled. That can lead to high compressor head TEMPERATURE even though the head pressure is low
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Re: Installed my A/C, compressor not kicking on???
[Re: Andrewh]
#351411
06/19/09 12:39 PM
06/19/09 12:39 PM
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Joined: Jan 2003
Posts: 21,081
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,081
Niles , Ohio
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Most hi cut off switches will only cut out when you hit 400 to 450 running.That proetects the system.Being over charged will not keep it from engaging period.You need a gauge that tells PSI not one that says over charged.The low side will go to ambient temp pressure when shut off.So if its 150 degreees under the hood the low side will show 150 with the compressor off.Not saying its not overcharged though.If it engages when jumped its a bad pressure switch blown fuse or a bad switch to turn it on.Check power into the compressor.That and try and jump the low cut off switch and see if it engages.A/C isnt a black art its fairly simple once you do a few hundred.Rocky
Chrysler Firepower
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Re: Installed my A/C, compressor not kicking on???
[Re: Challenger 1]
#351413
06/19/09 12:52 PM
06/19/09 12:52 PM
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Joined: Jan 2008
Posts: 2,592
None
71rm23
master
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master
Joined: Jan 2008
Posts: 2,592
None
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Quote:
I believe 2.5# is over charged. I have two challengers with AC and they both take about 1.8# of gas.
 If its R134, it takes less than R12 does. So, if the manual says 2 lbs of freon, R12, then it will be less for R134. Someone correct me if I'm wrong though.
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Re: Installed my A/C, compressor not kicking on???
[Re: RP's R/T's]
#351414
06/19/09 01:26 PM
06/19/09 01:26 PM
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Anonymous
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Anonymous
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Quote:
I don't want to Hijack the post...quick question on R12 versus other other refrigerants.
Is one better for a car that will sit?
Does the refrigerant affect the issue noted?
This is a moot question because R12 is no longer legal.
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Re: Installed my A/C, compressor not kicking on???
[Re: therocks]
#351415
06/19/09 01:32 PM
06/19/09 01:32 PM
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Anonymous
Unregistered
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Anonymous
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Quote:
Most hi cut off switches will only cut out when you hit 400 to 450 running.That proetects the system.Being over charged will not keep it from engaging period.You need a gauge that tells PSI not one that says over charged.The low side will go to ambient temp pressure when shut off.So if its 150 degreees under the hood the low side will show 150 with the compressor off.Not saying its not overcharged though.If it engages when jumped its a bad pressure switch blown fuse or a bad switch to turn it on.Check power into the compressor.That and try and jump the low cut off switch and see if it engages.A/C isnt a black art its fairly simple once you do a few hundred.Rocky
Basically correct, but you didn't say this very well.
THERE IS NO gauge that shows an overcharge.
The TEMPERATURE scale relative to the refrigerant used ON THE PRESSURE SCALE will show ambient temp, but this is true either high or low side, AND the system must sit long enough--overnight--for the engine to cool and for the system to actually reach ambient outdoor temperature.
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Re: Installed my A/C, compressor not kicking on???
[Re: Cudalord]
#351417
06/19/09 02:08 PM
06/19/09 02:08 PM
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Joined: Aug 2003
Posts: 309
Dearborn, Michigan
gtxncuda
enthusiast
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enthusiast
Joined: Aug 2003
Posts: 309
Dearborn, Michigan
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Ummm... not to insult anyone, but is there a fuse in the Classic system anywhere for clutch operation?  It worked when you applied a jumper correct? There's one in the OE systems. Worth a shot...
1971 Cuda 340 auto
2013 Mustang Boss 302 L/S
1969 Road Runner RM21 440 4 speed
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Re: Installed my A/C, compressor not kicking on???
[Re: Cudalord]
#351421
06/19/09 03:58 PM
06/19/09 03:58 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Well, I just put the jumper between the two connectors on the low pressure switch plug, and the compressor did engage. This tells me that there is no electrical problem. It has to be either a faulty switch (doubtful), or pressure is too LOW. Per the previous post, pressure too HIGH will NOT keep the compressor from engaging.
Correct?
Nope
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Re: Installed my A/C, compressor not kicking on???
[Re: Challenger 1]
#351423
06/19/09 04:59 PM
06/19/09 04:59 PM
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Joined: Jan 2003
Posts: 21,081
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,081
Niles , Ohio
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Even if its a hi lo switch an overchrge wont keep it from coming on.They shut it down when the hi or low pressures it high only.Charge a system it will be close to ambient temp till the compressor kicks on plain and simple.When you run the car the pressures go up when off because the under hood temp is higher.So if its 90 out they press will be around 90 psi.Then the drop and rise when the comp kicks on.When hi or low reaches a certain pressure they kick out then cycle back in.That and the probe in the evaporator also can shut down the compressor when it gets to 31 degrees so it dosent freeze.Rocky
Chrysler Firepower
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