Problem with the AC fan, it turns on and off.

[Breik]

Hello, I'm writing from Spain, I have a problem with my 2011 Mustang S197, 3.7, when I turn on the A/C, cold air comes out, but I have been able to verify that the radiator fan works for about 10 seconds and then turns off, after another 10 seconds it turns on and on continuously, sometimes when I accelerate hard, the air stops cooling for a few seconds and then starts cooling again. with the car stopped and with the A/C at full power I have been able to observe that the compressor is continuously working, but the fan does not... l on the other hand with the A/C off, I have been able to verify that the fan works well and continuously when the car heats up and has to cool. I hope you can help me, sorry for the language, but I am using a translator, greetings.

 

[86GT351]

Overheating: Fan Relay Bypass How-to

Had an overheating issue on my 2014 GT and through troubleshooting and research found that I was a victim of the dreaded “cooling fan drawing too much power and melting the connectors issue”. Cooling Fan Plug by SC_Stang posted Mar 31, 2022 at 1:27 AM For troubleshooting - If you turn your AC...

www.s197forum.com

 

[Robert Larimer]

Hello, I'm writing from Spain, I have a problem with my 2011 Mustang S197, 3.7, when I turn on the A/C, cold air comes out, but I have been able to verify that the radiator fan works for about 10 seconds and then turns off, after another 10 seconds it turns on and on continuously, sometimes when I accelerate hard, the air stops cooling for a few seconds and then starts cooling again. with the car stopped and with the A/C at full power I have been able to observe that the compressor is continuously working, but the fan does not... l on the other hand with the A/C off, I have been able to verify that the fan works well and continuously when the car heats up and has to cool. I hope you can help me, sorry for the language, but I am using a translator, greetings.

Your fan should come on and stay on whenever AC is on. There are 2 speeds for the fan. Low and High. The speed is controlled by a resistor on the fan shroud. First check to see if your fan comes on instantly when you switch AC on. That is the low speed fan. If it doesn't come on your resistor is faulty and you have no low speed fan. The high speed fan still works and will come on when the AC gas pressure gets too high and then cycle off when the pressure is lowered. That may be the cycling that you are experiencing. There are also problems with the connector for the fan wires melting but I don't think that would make it turn off and on. If you find your low speed fan is not working the easiest way to fix it is to replace the fan and shroud which will include a new resistor. The resistor alone costs nearly as much as the whole unit. Don't ask me why.

 

[Breik]

Your fan should come on and stay on whenever AC is on. There are 2 speeds for the fan. Low and High. The speed is controlled by a resistor on the fan shroud. First check to see if your fan comes on instantly when you switch AC on. That is the low speed fan. If it doesn't come on your resistor is faulty and you have no low speed fan. The high speed fan still works and will come on when the AC gas pressure gets too high and then cycle off when the pressure is lowered. That may be the cycling that you are experiencing. There are also problems with the connector for the fan wires melting but I don't think that would make it turn off and on. If you find your low speed fan is not working the easiest way to fix it is to replace the fan and shroud which will include a new resistor. The resistor alone costs nearly as much as the whole unit. Don't ask me why.

Hello, thank you very much for the response. I have verified that when I turn on the AC, the fan turns on for about 10 seconds, then turns off and turns back on after another 10 seconds have passed. Do I understand that the low speed is working? And is the high speed failing? For what reason might the high speed fail? I checked the connector and its condition is correct. Thank you very much for your help.

 

[Robert Larimer]

Hello, thank you very much for the response. I have verified that when I turn on the AC, the fan turns on for about 10 seconds, then turns off and turns back on after another 10 seconds have passed. Do I understand that the low speed is working? And is the high speed failing? For what reason might the high speed fail? I checked the connector and its condition is correct. Thank you very much for your help.

View attachment 109889

So the moment you flick on the AC the fan comes on or does it take a few seconds? Do you hear clicking sounds when it cycles off and on? There are 2 relays that control the fan in the fuse box behind the windshield washer reservoir. Try switching the locations of the high and low speed relays and see if that changes anything. They pull out to unplug. You could also unplug the high speed relay and see if your fan still comes on. Then you will know for sure if your low speed fan is working or not. This video will show where they are. The only situation that I know that would cycle the fan is when pressure in the AC gets too high and the high speed fan is triggered. The low speed fan has no situation like that. It stays on as long as the AC is on. It is usually the low speed fan that fails and I still think it is likely your problem. The resistor heats up and it fails. You can find it and examine it. It is by the plug for the fan on the fan shroud.

 

[Breik]

So the moment you flick on the AC the fan comes on or does it take a few seconds? Do you hear clicking sounds when it cycles off and on? There are 2 relays that control the fan in the fuse box behind the windshield washer reservoir. Try switching the locations of the high and low speed relays and see if that changes anything. They pull out to unplug. You could also unplug the high speed relay and see if your fan still comes on. Then you will know for sure if your low speed fan is working or not. This video will show where they are. The only situation that I know that would cycle the fan is when pressure in the AC gets too high and the high speed fan is triggered. The low speed fan has no situation like that. It stays on as long as the AC is on. It is usually the low speed fan that fails and I still think it is likely your problem. The resistor heats up and it fails. You can find it and examine it. It is by the plug for the fan on the fan shroud.

As soon as I turn on the AC, the fan starts running and blows cold air. After about 10 seconds, the fan stops and stays off for another 10 seconds, then starts running again, and so on. The AC compressor doesn't turn off; it keeps working. It's quite strange. The relays open and close, but I have to swap them to see if there's any change in operation.
Is the relay marked in red the high-voltage relay? And the low-voltage relay marked in blue?
Could it be related to circuit pressure issues? Thank you very much.

 

[Robert Larimer]

It is strange that the compressor is staying on. Could your fan motor be faulty? Does it feel hot? Yes relay #50 is the high speed relay and #55 is the low speed. Pull #50 out and see if you fan still turns on. All those large relays are identical so you can swap them at will. If it does not then that will verify that you low speed fan is not working. If it is the low speed fan still running and shutting off and on it is another problem that I have not seen. The smaller relay #7 provides power to the fan relays so you could check if that relay is turning off and on. Perhaps that relay is bad. You can feel them click if you can't hear them. Good luck.

 

[Breik]

It is strange that the compressor is staying on. Could your fan motor be faulty? Does it feel hot? Yes relay #50 is the high speed relay and #55 is the low speed. Pull #50 out and see if you fan still turns on. All those large relays are identical so you can swap them at will. If it does not then that will verify that you low speed fan is not working. If it is the low speed fan still running and shutting off and on it is another problem that I have not seen. The smaller relay #7 provides power to the fan relays so you could check if that relay is turning off and on. Perhaps that relay is bad. You can feel them click if you can't hear them. Good luck.

Hi, I've performed the following tests: - I disconnected relay 50, the fan doesn't work and the AC compressor doesn't work. - I connected relay 50 and disconnected relay 55, the fan works and stops as usual and the AC works. I've swapped the relays and there's been no change. I've tried another relay for the rear window fog light and everything remains the same... I think we can rule out a fault in the relays. I'll see if I can send you some videos so you can see how the fan works. Thanks.

 

[Breik]

This is the video of the fan working.

 

[Robert Larimer]

Hi, I've performed the following tests: - I disconnected relay 50, the fan doesn't work and the AC compressor doesn't work. - I connected relay 50 and disconnected relay 55, the fan works and stops as usual and the AC works. I've swapped the relays and there's been no change. I've tried another relay for the rear window fog light and everything remains the same... I think we can rule out a fault in the relays. I'll see if I can send you some videos so you can see how the fan works. Thanks.

I saw the video and you need a new fan and shroud. Your low speed fan is not working. You verified that by having no fan when you pulled the #50 relay. . The AC compressor doesn't work without a fan because the AC gas pressure is too high and it shuts off. I think that is happening to you when it cycles but you can't hear it because of the fan. There are several good aftermarket fan/shroud on Amazon for under $100 and they all include the resistor that will fix your low speed fan. It is an easy to do replacement and I have done it for the same reason. Meanwhile do not run your AC as that high pressure is bad for the compressor and you may burn it out. You old fan has had many years of workouts and it is a good idea to replace it now anyway.
This is the link to the one I bought in 2021 and is still working perfectly. You can see the ceramic resistor about 1/3 down the left side. It is better than the OEM one. I see you have a Pony Package Mustang like mine. It's a beauty. Hang on to it.
https://www.amazon.com/dp/B000VKPRNY?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_3

 

[Breik]

I saw the video and you need a new fan and shroud. Your low speed fan is not working. You verified that by having no fan when you pulled the #50 relay. . The AC compressor doesn't work without a fan because the AC gas pressure is too high and it shuts off. I think that is happening to you when it cycles but you can't hear it because of the fan. There are several good aftermarket fan/shroud on Amazon for under $100 and they all include the resistor that will fix your low speed fan. It is an easy to do replacement and I have done it for the same reason. Meanwhile do not run your AC as that high pressure is bad for the compressor and you may burn it out. You old fan has had many years of workouts and it is a good idea to replace it now anyway.
This is the link to the one I bought in 2021 and is still working perfectly. You can see the ceramic resistor about 1/3 down the left side. It is better than the OEM one. I see you have a Pony Package Mustang like mine. It's a beauty. Hang on to it.
https://www.amazon.com/dp/B000VKPRNY?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_3

Great!!! Thank you so much for all your help. Do I understand that the fault is in the fan resistor or in the fan motor? The problem I have is that to bring any spare part to Spain, I have to invest triple what it costs in the USA, for shipping and customs... so I want to be completely sure of the fault. I've seen on AliExpress that they sell the fan resistor for very little money. I think I'm going to buy it just to check if it's really the resistor that's at fault and then order the complete fan from the USA. Do you think I could run any other tests to diagnose the fault? Thank you very much. The reference for the resistor is 7R3Z8L603A?

 

[Robert Larimer]

Great!!! Thank you so much for all your help. Do I understand that the fault is in the fan resistor or in the fan motor? The problem I have is that to bring any spare part to Spain, I have to invest triple what it costs in the USA, for shipping and customs... so I want to be completely sure of the fault. I've seen on AliExpress that they sell the fan resistor for very little money. I think I'm going to buy it just to check if it's really the resistor that's at fault and then order the complete fan from the USA. Do you think I could run any other tests to diagnose the fault? Thank you very much. The reference for the resistor is 7R3Z8L603A?

View attachment 109979

Your high speed fan works so it is not the fan motor. The resistor should fix your fan but you should check your original one with a meter too. Are you sure that resistor is for 2011 to 2014? S197's from 2005 to 2010 use a different one. I don't know what the difference is and it may not matter. I believe the one you are looking at is a Chinese made aftermarket part. It may work fine or it might not. I know when I look here in the US for the 2011 up resistor it's $100+ That is why I bought the entire fan assembly with the resistor in it. It was cheaper. It is just a dumb resistor so your Aliexpress one will probably be fine at least until you get a new fan. Keep me informed how it goes. The Ford part number for the 2011-2014 fan resistor is #BR3Z8L603A and I just noticed that the plug is different. I think you can just swap in your old plug and make it work. The rest of it is the same.

https://ford.oempartsonline.com/oem-parts/ford-resistor-br3z8l603a

https://www.fordpartsgiant.com/parts/ford-resistor-asy_br3z-8l603-a.html

 

[allexanderlee]

Hey @Breik, if you haven't fixed the issue yet... just recently I had an exact same problem with my Stang. I was also unsure about the exact issue, it turned out that one of my fan resistor legs was fried but still maintained some contact.
I bought an OEM used fan & shroud assy with the resistor from the junkyard here in Europe. Ended up being cheaper than getting the new OEM resistor separately - around EUR 120 shipping included. I swapped only the resistor, 15 min job, works like a charm.
Mind the correct connector to the fan motor itself, as Robert correctly noticed. The one in your picture is 2005-2009.