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Discussion Starter #1 (Edited)
This problem seems to be getting worse and worse. When the AC fan at the front of the engine turns on the whole car rumbles for about few seconds. This happens intermittently as the fan turns on and off. Sometimes It seems as if its about to die like the AC is taking too much power. I just replaced the battery a few months ago. It does not sound good for the engine. Any idea what the cause of this is and or if its normal? I hope I don't need a new AC compressor -_-
 

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Have you noticed this happening when the AC is off? I'm assuming the fans plug and resistor are okay if it works in low without the rumble you mentioned. If you turn the AC on, it will kick on the cooling fan in high and will stay on until you turn off the AC. Maybe the motor, blade, or shroud is starting to fail. I would inspect the fan assembly to see if it's loose or there is any other damage that you can see.
 

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When you replaced your battery, did you test the charging system to verify that the alternator output is within specifications?

In any event, that is where I would begin the diagnosis.... A charging system test, and scan for any Diagnostic Trouble Codes that may be present.
 

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Discussion Starter #4
It does not happen when the AC is off and I noticed after further inspection that its not the fan that is making the rumble it is actually the AC compressor. Also the fan does not stay on. It will switch on and off every 15-30 seconds. So the compressor makes some noise and then the fan kicks on almost in sync so it sounded to me like the fan sitting in the drivers seat, until I opened the hood and stuck my head in there. lol
 

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Discussion Starter #5
I did not but this is a good idea to test the alternator. My car has a self test diagnostic menu where it shows that the charging system is okay. My bro had on 08 stang and his notified him that there was an issue with the charging system before his alternator went out but it did need replaced so I never took it to autozone because I felt the self test was sufficient.
 

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Try cleaning the throttle body and checking the air filter. If either of these are dirty it can do exactly what you are describing.
 

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I did not but this is a good idea to test the alternator. My car has a self test diagnostic menu where it shows that the charging system is okay. My bro had on 08 stang and his notified him that there was an issue with the charging system before his alternator went out but it did need replaced so I never took it to autozone because I felt the self test was sufficient.
Hmmm.
Newfangled technology.

I guess that someday they will make cars that drive themselves to the nearest service center, in the middle of the night, to be repaired by a robot, and then return to your home before you wake up in the morning! :)
 

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It does not happen when the AC is off and I noticed after further inspection that its not the fan that is making the rumble it is actually the AC compressor. Also the fan does not stay on. It will switch on and off every 15-30 seconds. So the compressor makes some noise and then the fan kicks on almost in sync so it sounded to me like the fan sitting in the drivers seat, until I opened the hood and stuck my head in there. lol
In my 2012 model the fan stays on constantly while the AC is on, cycling like you describe will wear out the fan relay pretty quick. You might try researching that problem, it might be related.
 

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Discussion Starter #9
In my 2012 model the fan stays on constantly while the AC is on, cycling like you describe will wear out the fan relay pretty quick. You might try researching that problem, it might be related.

Yeah this was a concern of mine with it constantly kicking on and off. It may wear out some parts. I think it probably is related. AC work is not cheap. Most shops will charge close to $100 just to diagnose the issue.
 

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Discussion Starter #10
Yeah this was a concern of mine with it constantly kicking on and off. It may wear out some parts. I think it probably is related. AC work is not cheap. Most shops will charge close to $100 just to diagnose the issue.
Read online that this rapid cycling may be caused by the system being overcharged which may be the issue because I did put some freon in it last year because it was not blowing as cold as it used to. But others also said this cycling is normal and mainly happens when the system is on low and not high, I never run the system on high because it gets perfectly cold on low. So I will have to test that if it does not happen on high.

I will also have to check the pressure, not sure about the high side but I saw online the low side should be aprox 25-30psi. I also saw some other posts from people describing the same rumbling/cycling and they claim their dealership for the most part claims that this is normal operation. They also claim the rumbling may be due to the idle calibration or something to do with the adaptive shifting feature which I do reset ever few 1000 miles with the fuse 47 pull.

Im going to take it to AutoZone to be load tested in a few hours and have an appointment Wednesday to have a professional check out the AC system also have something rattling in the suspension that needs looked at so might as well get it all checked out. And they told me if they found no issue with the AC system there would be NO diag fee so that is a relief.

I'm afraid this rapid cycling is going to cause something to wear out faster than normal leading to a more expensive repair. I hope its as simple as releasing some of the pressure. Which a lot of people said helped them.
 

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when you turn on the AC compresor, the rpm has to icrease around 200+ up idle in order to avoid it. if the idle is the same with AC on and AC off you have to check your ECM configuration or check your pulley or belt tensioner
 

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Discussion Starter #13 (Edited)
Load test passed as expected, took it to a local shop called tireman and they did an AC service where the claim that the level was low and there may be a leak. Its a 2011 with 25k miles I only drive during the summer months and store it during the winter so I would be surprised and honestly doubt it was even low because it was working fine and blowing cold air.

Idk how it could be low but they put dye in the new stuff. So they evacuated the system weighed it and then refilled to proper spec. But the short cycling issue still remains which I was afraid would happen. Now I feel like I wasted $85. On top of that they claim it will cost $110 to diagnose. The compressor seems to not be cycling as much but the radiator/blower fan is literally turning on and off every 15 seconds. I will be posting a video.
 

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Load test passed as expected, took it to a local shop called tireman and they did an AC service where the claim that the level was low and there may be a leak. Its a 2011 with 25k miles I only drive during the summer months and store it during the winter so I would be surprised and honestly doubt it was even low because it was working fine and blowing cold air.

Idk how it could be low but they put dye in the new stuff. So they evacuated the system weighed it and then refilled to proper spec. But the short cycling issue still remains which I was afraid would happen. Now I feel like I wasted $85. On top of that they claim it will cost $110 to diagnose. The compressor seems to not be cycling as much but the radiator/blower fan is literally turning on and off every 15 seconds. I will be posting a video.

I was going to say that your coolant level it's probably low. This will cause what you were talking about on any vehicle. You might have a fine crack in the line somewhere I got one last year when I hit a big pothole. I found the Crack by adding AC coolant with the glow stuff in it and black lighted it. I got the replacement part it was an easy swap and then I paid 150 for a recharge problem solved.
 

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Discussion Starter #15
Okay so update. I took it to Firestone and they checked it out and said the rapid cycling is definitely not normal and the charge is correct and that the fuses, switches and relays are NOT the issue and that the fan only works when the high pressure switch is on and not when the low pressure switch is on.

I still have to have it further diagnosed but currently do not have the money to pay someone $500 to fix it.

I am thinking it may be an issue with the resistor like iguanaman described.

---------- Post added at 12:29 PM ---------- Previous post was at 12:29 PM ----------

Okay so update. I took it to Firestone and they checked it out and said the rapid cycling is definitely not normal and the charge is correct and that the fuses, switches and relays are NOT the issue and that the fan only works when the high pressure switch is on and not when the low pressure switch is on.

I still have to have it further diagnosed but currently do not have the money to pay someone $500 to fix it.

I am thinking it may be an issue with the resistor like iguanaman described.
 
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