My 2.0 TDI Golf Mk V is coming up to 4.5 years old, and 73k.
Recently, the engine fan has started kicking in on a regular basis, far more regularly than it used to, and at times when you wouldnt expect, such as when the engine is cold after being sat for a couple of days (amoungst others). I know it is summer and therefore the fan will kick in when sat in traffic etc, but this is far more regular than that.
I have checked the coolant level, which is all fine. The car was only serviced last month and has a full VW history.
Any ideas what this might be? Something to do with the control module, or something more sinister?
I appreciate nobody can really diagnose over the internet, but wondered if this was a common fault........ or the starts of soemthing more serious (HG failure?)..........
Thanks in advance.
Edited by Pugugly on 11/08/2009 at 13:17
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Is it your aircon? The fan kicks in when the aircon is in use.
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If the set up is anything like the MK4s then when climate is on the fans run constantly at slow speed, if the resistors inside the fans blow (very, very common) then the fans will pulse on / off on fast speed.
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Isn't the coolant temp sensor on VAG cars notoriously unreliable? Easy and cheap to replace.
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The temperature gauge on the dash reads normal, and theres no error messages on the usually uber sensitve driver display..... resitor problem sounds like it could be a good place to start though, many thanks.
Its louder than just the aicon fan running, sounds like the full engine fan is kicking in....
Edited by Webmaster on 12/08/2009 at 01:14
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Diagnosis:
Switch the aircon off and the fan will go off. Switch it back on and after a short while the fan will start again and make the noise. Do so with the bonnet open and it is easy to see as well.
What's going on:
You may have two fans, one of them is electric, the other belt driven. The electric fan is partly controlled by the aircon. When the aircon is working it switches the fan on and off in intervals, irrespective of outside or engine temp. The electric fan is a two speed fan and he aircon switches it only on at low speed. However the speed is controlled by a resistor (I hope that is right) and if this is broken the fan will always spin full speed, even if the aircon requests slow speed.
Repair:
VW will want to sell you a full assembly, which is several 100 pounds. On the net you can also find people who have taken it apart and repaired the resistor.
Why to repair:
Cycling at full speed wears out the fan motor and hence it can fail, which could then lead to overheating if you really need the fan with hot weather and hot engine temp.
Why not to repair:
If the worst happens and the fan breaks then you still have the other fan working if necessary.
If the fan breaks you will notice as the noise will be gone.
I am currently doing a long term test. So far after being broken for 4+ years and counting the fan still spins happily at full speed. (Y2000 Passat)
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A few inaccuracies here. The Passat has one engine driven viscous coupled fan and one electric fan. The Golf has two electric fans.
On the Golf, VAG stupidly put the speed reducing resistors inside the motor and the whole lot ends up fried. The Passat (B5.5) has a slightly better set up with a resistor box on the LH front chassis rail.
If the low speed resistor fails open, the fan will be unable to run continuously at low speed when the air con is selected. This results in an intermittent demand for full fan speed from the system - as you are experiencing. Do not neglect fan problems - especially on the transverse engened cars where no mechanical fan drive is available.
659.
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I've recently done "Big Als" fan fix to my MK4 golf v5 estate and alls good again, it bypasses the damaged internal resistors using a pair of RS Components sourced external resistors mounted on a heat sink connected to the fast side of the fans to give slow and fast speed twin fans again.
website.lineone.net/~alan.james.lorely/fan%20mod/R...l
;o)
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