coolant fan running when cold and engine off

[viking64 10]

Hi

 

Have a 2.0 16v and found my battery flat.

Charged it back up and now found the coolant/engine fan running on its own.

Started it tonight to check and runs fine, turned off and was giving it a clean and after about 40 minutes the fans started( Engine cold only run for about 2 minutes) on full speed and would not go off. Had to disconnect the fan to get it to stop. Guess this was why the battery was flat!!

Anyone had a similar problem?

 

cheers

[vw rule 19]

Hello there,

 

possibly could be the radiator fan sensor switch, usually is screwed into radiator on the passenger side at bottom,

it'll have 3 or 4 wires going into connector plug. Normally this sensor burns out and doesn't turn the fan on, so what I've done in the past is remove the connector plug, and bridge the terminals with a small split pin to switch the fan on continuously, until I got home to replace the radiator temp sensor switch.

 

BUT IN YOUR CASE the fan is on continuously already, so like I say possibly the radiator fan temp switch has burnt out in a way that it causes your fan to run on.

 

Also there's a smaller over run fan switch attached to the valve cover, at the front left it screws into a small bracket, which it self is attached like I say to the front left of the valve cover.

This sensor is yellow I think and only has the one wire connected to it, this temp sensor tells the fan to switch on if it detects excess heat still in engine bay, normally after a journey for more than 20 minutes or if the engine has been working hard, it'll tell the fan to come on and go off every 2 minutes until the temperature in the engine bay has been reduced enough.

But these don't often go wrong, it's usually the main radiator fan temp sensor switch that play up, or it could be a wiring fault or slightly corroded warn contacts in the connector plug to fan switch.

 

 

Hope this helps

 

Si

[viking64 10]

Hi si

 

Thanks for the advice, will check them when I get home from work tomorrow and let you know what I find.:thumbleft:

 

Phil

[fendervg 33]

I had this a couple of years back and it was a faulty temp sensor switch in the radiator - replaced that and it sorted itself.

[vw rule 19]

Also check your coolant hoses because if any are showing signs of wear, it could be a good time to change them if they are bad.

The metal pipe that runs under the distributor and over the top of the gearbox slightly, this pipe is known to rust through.

Also the long coolant hose from the top of expansion bottle, to top of radiator on drivers side are also known to perish.

Also check your radiator at the bottom as they can leak sometimes.

 

VW Heritage have reproduced the top coolant hose for the 16v Corrado's / MK2 Golf 16v with engine codes (9A KR PL)

Part n.o 191 121 101 AC

This item has been obsolete for a while but is back in stock, I think they've got roughly 100 left in stock, cost is about £12

 

Si

Edited September 11, 2018 by vw rule

[viking64 10]

Have ordered a sensor.

Found a bit of water and corrosion in the sensor and connector. connector looks good so hopefully the sensor will fix it.

Thanks for the information and will let you know when I have fitted it.

 

Phil

[vw rule 19]

Hello Phil,

 

when you receive your new fan temp sensor it should ideally come complete with a washer,

this should be adequate but what I do as a extra precaution is put a very small amount of sealant over the washer to help it seal.

Erm the sealant I use and have used for years is called Hylomar Blue joint compound, this is the best stuff for any coolant housing or water pump, and you can use it for valve cover and sumps, it honestly is great stuff.

 

Ebay link

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F271386779392

 

Possibly Halfords sell it or Motorbitz.

 

Also you'll need a 27mm or 29mm spanner or socket to remove the old fan sensor, and only remove it when the engine is cold.

 

Si

Edited September 12, 2018 by vw rule

[_Matt_ 32]

I'm in the process of doing this job myself - I've bought both types of rad fan sensors as wasn't sure what I had whilst ordering at work. Both need a 29mm deep socket. Sadly I guessed and bought a 28mm DOH!

 

I'm also having a fan issue - I've replaced my thermostat and all 3 sensors in the stat holder - my old stat was stuck open but now the car is running right i've found the stage 1 fan does not come on. Stage 2 comes on once temps get higher. Stage 1 does come on when I turn the ignition off (this works off information off the yellow sensor in the stat though). Whilst the car is running stage 1 is controlled via the rad fan sensor so I am hoping it will fix the issue.

 

Sounds like yours might be similar but it's stuck reading a higher temperature so remains on!

 

Fun times. Good luck with yours.

[viking64 10]

New sensor fitted and all good so far.

Didn't have a 29mm deep socket but managed with a spanner.

Thanks for the help

Phil

[viking64 10]

Sounds like mine was stuck on stage 2.

Replaced the sensor now working as it should 👍

[vw rule 19]

Hello Phil,

 

good to hear it's all sorted nice one :salute:

 

Si

[_Matt_ 32]

Good to hear Phil. I've just swapped my sensor out and my issues are fixed too. Phew!