Not Your Average A/C Problem
07-02-2006, 02:53 PM
#1
Thread Starter
Join Date: Jul 2006
Posts: 6
Not Your Average A/C Problem
my son owns a 2004 Mustang GT SOHC 4.6L which recently developed a problem with the air conditioning control system.
basically when the A/C should be on, it's off; when it should be off, it's on. more specifically, when the A/C control switch on the dash is turned to A/C, or A/C MAX, the compressor shuts down (compressor clutch disengages). when the dash **** is rotated to any other position, the compressor comes on (compressor clutch engages) and the system will blow cold air through the vents.
there is another symptom of this problem which may help in (or further complicate) the diagnosis. normally, when the engine is running at very high rpms, the A/C compressor is designed to shut down so as not to cause damage to the compressor. instead, now when he accellerates to high rpms, the compressor turns on and starts blowing cold air.
he recently added a turbocharger to the car. could this in any way be related to the change in the automatic A/C control system? what else might be causing this problem (the dash selection switch, a computer chip)? has anyone else experienced this problem?
thanks in advance for any insights you might offer.
basically when the A/C should be on, it's off; when it should be off, it's on. more specifically, when the A/C control switch on the dash is turned to A/C, or A/C MAX, the compressor shuts down (compressor clutch disengages). when the dash **** is rotated to any other position, the compressor comes on (compressor clutch engages) and the system will blow cold air through the vents.
there is another symptom of this problem which may help in (or further complicate) the diagnosis. normally, when the engine is running at very high rpms, the A/C compressor is designed to shut down so as not to cause damage to the compressor. instead, now when he accellerates to high rpms, the compressor turns on and starts blowing cold air.
he recently added a turbocharger to the car. could this in any way be related to the change in the automatic A/C control system? what else might be causing this problem (the dash selection switch, a computer chip)? has anyone else experienced this problem?
thanks in advance for any insights you might offer.
07-02-2006, 03:12 PM
#2
4th Gear Member
Join Date: Jan 2006
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Posts: 1,143
RE: Not Your Average A/C Problem
wow a turbo, must be nice. my first guess which is probably wrong, but it could be a vacuum line. otherwise i would say its in the ecu or programmer. you try to put the stock tune on for kicks? did this happen right after the turbo install?
07-02-2006, 05:49 PM
#3
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Join Date: Sep 2005
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Posts: 5,128
RE: Not Your Average A/C Problem
sounds like an electrical wire got switched around somewhere... vacuum only control where the air comes out, not the temperature of it or the compressor
that's goofy tho, but it's in the wiring
that's goofy tho, but it's in the wiring
07-02-2006, 06:18 PM
#4
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Join Date: Jul 2005
Location: Georgia
Posts: 2,387
RE: Not Your Average A/C Problem
ORIGINAL: monkeydude3
sounds like an electrical wire got switched around somewhere... vacuum only control where the air comes out, not the temperature of it or the compressor
that's goofy tho, but it's in the wiring
sounds like an electrical wire got switched around somewhere... vacuum only control where the air comes out, not the temperature of it or the compressor
that's goofy tho, but it's in the wiring
07-03-2006, 12:42 AM
#6
Thread Starter
Join Date: Jul 2006
Posts: 6
RE: Not Your Average A/C Problem
my son informs me that technically it was a supercharger he installed on his 2004 Mustang, which i understand is only activated during low vacuum (acceleration) conditions. the A/C problem however exists pretty much all of the time: A/C compressor shuts down when A/C is selected at the dash control **** (no cooling), on when anything else (normal ventillation) is selected. he does not have 'climate control', just the basic ventillation system with A/C. although the problem developed "sometime after" the supercharger installation it would seem unlikely that the supercharger is actually related to the A/C problem. still looking for ideas, suggestions, similar experience...
07-03-2006, 01:04 AM
#7
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Join Date: Aug 2005
Location: Whitehall, Michigan
Posts: 2,638
RE: Not Your Average A/C Problem
We've got a couple of conditions here, and at least I need clarification...
1) A/C compressor is engaging (the radiator fan would be on at all times too)... you'll hear it click quite audibly from outside the car, all the normal signs of the A/C being on...
2) Fan for air being on... for here, air is coming out of the vents, regardless of the temperature of said air
Now... when it's set to off, the A/C compressor won't be engaging, and the fan should not be blowing any air... simple enough...
The fan SHOULD be blowing air when it's set to vent or floor... for these two, the A/C compressor will NOT engage
When it's set to anything else: A/C, Max A/C, Defrost/Floor, and just Defrost, the A/C compressor WILL engage, regardless of what the temperature **** in the center is set to.
Now, when you switch between these, you should hear a small amount of air flowing as it uses the vacuum to redirect the flow of air, I'd assume that's happening normally. Vent, A/C, and Max A/C should all have the same position and not make any sound (all the ones counter-clockwise of "Off")... all the ones clockwise should make sound when they switch. Bad explaination but that's the best I can give you
If this is the way that section is performing, the vacuum set up should all be normal and working properly.
If the A/C compressor is coming on when you set it to say, floor, or vent, and it is off when you have it on A/C or any other setting where it should be on, but isn't, you have an electrical problem that probably won't be so easily solved... you'll have to find some wiring diagrams and have an understanding of the connections to the ECU to be able to tackle the problem... if it's electrical, I'd just take it to Ford and have them correct the problem.
Edit: The wiring is amazingly confusing at best. For example, I swapped my instrument cluster to that of a 99 Cobra, in that year, the rear defroster button was right below the headlight ****, and physically connected the circuit. In 04, the button is in the center near the shifter, and just toggles the circuit, does not make a connection. My rear defroster is always on, unless I pull the fuse for it in the engine bay... and when I push the button for the rear defroster, regardless if the engine bay fuse for it is in or not, it blows the fuse for the A/C compressor clutch, 100% of the time. If you can explain how that's all tied together, go for it That's just a peek at the challenge you're in for if you attempt to tackle the electrical issues yourself. I personally got a diagram (from Tac2cul, THANKS AGAIN!) and am going to try modifying some things to fix my problem.
Edit 2: The A/C compressor cycles! I haven't mentioned and am not sure if you are aware of it. When you set it to A/C the compressor will cycle on and off, you'll hear it click each time it does. When it first comes on after a period without use (or when it is heat-soaked) it may take a while to finally click back off, 30-45 seconds at 2000 RPM... after that the average on-time is 5-10 seconds, followed by 10-15 seconds of off-time, then it cycles back on etc...
Also, it does have a WOT switch, when the RPMs get high, the compressor clutch will disengage, as you said, to stop damage to the compressor... cold air may still be coming out of the vents at this point, the fan will stay on. When the RPMs get back down low the compressor clutch will resume what it should have been doing. It's electrically controlled, and will require delving into the Mustang electrics. What you were saying is that, when the RPMs get high the fan comes on and starts blowing air? That's part of the reason I need clarification.
1) A/C compressor is engaging (the radiator fan would be on at all times too)... you'll hear it click quite audibly from outside the car, all the normal signs of the A/C being on...
2) Fan for air being on... for here, air is coming out of the vents, regardless of the temperature of said air
Now... when it's set to off, the A/C compressor won't be engaging, and the fan should not be blowing any air... simple enough...
The fan SHOULD be blowing air when it's set to vent or floor... for these two, the A/C compressor will NOT engage
When it's set to anything else: A/C, Max A/C, Defrost/Floor, and just Defrost, the A/C compressor WILL engage, regardless of what the temperature **** in the center is set to.
Now, when you switch between these, you should hear a small amount of air flowing as it uses the vacuum to redirect the flow of air, I'd assume that's happening normally. Vent, A/C, and Max A/C should all have the same position and not make any sound (all the ones counter-clockwise of "Off")... all the ones clockwise should make sound when they switch. Bad explaination but that's the best I can give you
If this is the way that section is performing, the vacuum set up should all be normal and working properly.If the A/C compressor is coming on when you set it to say, floor, or vent, and it is off when you have it on A/C or any other setting where it should be on, but isn't, you have an electrical problem that probably won't be so easily solved... you'll have to find some wiring diagrams and have an understanding of the connections to the ECU to be able to tackle the problem... if it's electrical, I'd just take it to Ford and have them correct the problem.
Edit: The wiring is amazingly confusing at best. For example, I swapped my instrument cluster to that of a 99 Cobra, in that year, the rear defroster button was right below the headlight ****, and physically connected the circuit. In 04, the button is in the center near the shifter, and just toggles the circuit, does not make a connection. My rear defroster is always on, unless I pull the fuse for it in the engine bay... and when I push the button for the rear defroster, regardless if the engine bay fuse for it is in or not, it blows the fuse for the A/C compressor clutch, 100% of the time. If you can explain how that's all tied together, go for it
That's just a peek at the challenge you're in for if you attempt to tackle the electrical issues yourself. I personally got a diagram (from Tac2cul, THANKS AGAIN!) and am going to try modifying some things to fix my problem.Edit 2: The A/C compressor cycles! I haven't mentioned and am not sure if you are aware of it. When you set it to A/C the compressor will cycle on and off, you'll hear it click each time it does. When it first comes on after a period without use (or when it is heat-soaked) it may take a while to finally click back off, 30-45 seconds at 2000 RPM... after that the average on-time is 5-10 seconds, followed by 10-15 seconds of off-time, then it cycles back on etc...
Also, it does have a WOT switch, when the RPMs get high, the compressor clutch will disengage, as you said, to stop damage to the compressor... cold air may still be coming out of the vents at this point, the fan will stay on. When the RPMs get back down low the compressor clutch will resume what it should have been doing. It's electrically controlled, and will require delving into the Mustang electrics. What you were saying is that, when the RPMs get high the fan comes on and starts blowing air? That's part of the reason I need clarification.
07-03-2006, 01:49 AM
#9
Thread Starter
Join Date: Jul 2006
Posts: 6
RE: Not Your Average A/C Problem
so far it sounds like the consensus is this is an electrical problem. will try to find out more about what may have occurred to cause this and reply in the next day or so. thanks for your help.
07-03-2006, 02:07 AM
#10
Thread Starter
Join Date: Jul 2006
Posts: 6
RE: Not Your Average A/C Problem
what happens when the dash selector is set to "off"?; where is it when the compressor switches on during high rpms?, etc. you raise some good questions. my son (who has the problem) lives in another city (good mechanic, no internet access unfortunately), so responses to questions may be delayed for a day or two. i will reply, and appreciate all the feedback. also when the solution is found (even if it involves taking it to a Ford service center which we're trying hard to avoid) i will post it. thanks everyone...