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RichardM1126, Auto Mechanic
Category: Car
Satisfied Customers: 48
Experience:  Licensed diagnostic and repair technician
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Looks like my radiator fan isnt coming on when i turn my air

Customer Question

Looks like my radiator fan isnt coming on when i turn my air con on, I want to check the fuses and relays but dont know which ones i need to check and the manual for my car is not helpful
JA: How many miles are on the car? Has the car been starting normally?
Customer: 81k yes starts and works fine
JA: What is the make/model/year of your car?
Customer: Mini Cooper S 2008
JA: Are you fixing your MINI yourself? What have you tried so far?
Customer: Well i want to check the fuses and relays first before i try and take it somewhere as if its just a blown fuse i can easily fix that
JA: Is there anything else the Mechanic should know before I connect you? Rest assured that they'll be able to help you.
Customer: no
Submitted: 15 days ago.
Category: Car
Customer: replied 15 days ago.
I can take a picture of the engine bay fuse box if that would be helpful?
Expert:  RichardM1126 replied 15 days ago.

Hi my name is ***** ***** with the aircon does the light come on the switch when turned on? does the compressor start working when you switch the aircon on? if these aren't working the fan will not start  to spin, has the system been serviced lately? aircon systems are recommended to be serviced and gas topped up every 2 years as the system is designed to slowly loose gas and if not serviced and the level gets low it switches it self off to prevent damage to the system,

these sections will need to be checked first before disturbing fuses etc, if you do have blown fuses the question is why? just replacing a fuse will not fix the problem,

checking the light and compressor are quick checks if they are not working the actual aircon system will need checking by a garage

Customer: replied 15 days ago.
Hiya, the system was service about 2 weeks ago in the sense it was refilled and the technician at the time said the air con system itself was fine, no leaks etc but that the fan did not come on when the air con was activated
Customer: replied 15 days ago.
the light does indeed come on when i press the air con button
Customer: replied 15 days ago.
I would say the compressor does start as when I press the air con button a noticable change in revs occurs
Expert:  RichardM1126 replied 15 days ago.

Hi that does sound like its kicking in, did the technician do a service as in drain the system do a vacuum check and check for leaks adding a leak dye? usually around £60 and takes about an hour?

Customer: replied 15 days ago.
He did check the pressure in the system before he did the refil and said that the pressure was fine
Customer: replied 15 days ago.
the air con does work if im traveling at speed, but at a stand still it does not blow cold air
Customer: replied 15 days ago.
40+ mph, its nice and cold
Customer: replied 15 days ago.
but in traffic it just blows warm air
Expert:  RichardM1126 replied 15 days ago.

checking the pressure isn't checking the system that just tells him that there is some gas in the system, do you know how much he drained out before he serviced it can be anything like 750 grams, it does sound like you have a fan issue then, does the fan cut in to cool the normal radiator down? have you 2 fans or one that just does the normal radiator and aircon?

Customer: replied 15 days ago.
It looks like just the one fan to me. The engine hasn't been overheating and does come on if you leave the car running for 20mins or so
Expert:  RichardM1126 replied 15 days ago.

Some times they have a fan the engine side and one the front bumper side, so if it only has one fan and it cuts in regarding normal engine temperature for the coolant we can safely say the wiring and fuses etc for the fan are ok as it wouldn’t work at all, it is leading more to the control unit not sending signal to the fan I’m afraid, do you have any diagnostic scanners?

Customer: replied 15 days ago.
There is only 1 relay in the engine bay fuse box. Yes ive got an ODB scanner arriving today
Expert:  RichardM1126 replied 15 days ago.

Can you hear the relay working? In theory if the light is coming on and the compressor is cutting in that side of the electrical system is working it the part from the ecu/body control module to switch fan on that needs chec*****, *****’t be fooled into thinking the relay is faulty if not working as if it’s not getting a signal it won’t work,

Customer: replied 15 days ago.
How can I check if the relay is working
Expert:  RichardM1126 replied 15 days ago.

Firstly can you hear it clicking when you turn aircon on and off? also you can check if its getting a live feed and earth,

Customer: replied 15 days ago.
ok, ill go and check that out
Expert:  RichardM1126 replied 15 days ago.

ok no problem hope you get to the bottom of it, many thanks

Customer: replied 15 days ago.
when i get my ODB scanner is there something i should be looking for?
Expert:  RichardM1126 replied 15 days ago.

See if any faults are stored for the aircon system might be some relating to pressure or signal loss, also if it has a live data feature see what the pressures are running at, this is done with the engine running anf aircon switvched on

Customer: replied 15 days ago.
great, ill check that to, thanks
Expert:  RichardM1126 replied 15 days ago.

no worries many thanks