Radiator Fan only working when the engine is turned off.

R

rapida_chris

Member
Here's my problem.

2004 16 FSI

Start the car from cold and drive for approximately 10 minutes and the car reaches normal temperature of 90 (needle is in absolute centre).
The temperature stays at normal for aboutr 27 to 30 minutes then the car begins to overheat and the needle slowly starts to climb higher until it reaches 120.

When checking under the bonnet the fan is not turning, but turn off the ignition and the fan will start to turn and keep turning until the car has reached normal temperature.

If I turn on the engine before the car has cooled down to normal temperature the fan stops turning, turn engine off again and the fan will start and cool the engine down to normal.

Also if I leave the climate control on the fan runs continuously as it should at a lesser rate.

So it seems the main cooling action of the fan doesn't want to work after approximately 30 minutes.

The thermostat and housing were changed about two years ago as well as lots of pipes.

Ideas anyone, please.
 
Sorry Chris, its the silver unit that sits at the top of the fan with the connectors going into it. Very easy part to change.
 
50225


This, albeit mime would be £10 plus postage
 
Checked my fuses for the Radiator fan Radiator fan thermo-switch and also
the Radiator fan control unit fuse (S142) all OK.

Power is getting to the Fan control module which sits on top of the radiator.

Something new the hot air blower will not blow hot air it just blows and the climate control doesn't seem to be controlling anything, just blowing.

Car still overheats after approximately 27 minutes but switch off the engine and do one turn on the ignition and the fan kicks-in and cools the engine down to normal. Start the engine again and the fan will stop running and the car goes back into overheating!
 
Temp sensor or its wiring faulty can cause this. Now you are saying no cabin heat, that sounds more like a blockage or air lock in the coolant sytem or even a faulty water pump. Are you seeing flow back into the expansion tank?
 
For info, the fan is designed to run after switching off when the engine is hot. With no coolant flow via the water pump the latent heat stored in the engine block can cause 'afterboil' unless the fans continue to run. I think this is triggered by the tem sender in the bottom radiator hose.

Cheers Spike
 
audifan said:
Temp sensor or its wiring faulty can cause this. Now you are saying no cabin heat, that sounds more like a blockage or air lock in the coolant sytem or even a faulty water pump. Are you seeing flow back into the expansion tank?
Click to expand...

Yes audifan there is flow back into the expansion tank. Also there are no squeaking noises as you sometimes get with a worn water pump.

Thanks for your time audifan
 
Last edited:
spike said:
For info, the fan is designed to run after switching off when the engine is hot. With no coolant flow via the water pump the latent heat stored in the engine block can cause 'afterboil' unless the fans continue to run. I think this is triggered by the tem sender in the bottom radiator hose.

Cheers Spike
Click to expand...

So this means the temp sender in the radiator hose is good. So what tells the radiator fan to run when the engine is running?

Is it the job of the engine cooling sensor (the green thing looks a bit like a shotgun cartridge that I've seen pictures of) or is it the job of the thermostat.

But if it is the job of the thermostat then why am I getting correct readings on my temperature gauge.

Thanks for your time Spike
 
Hi Chris,

Quick go at answering your questions, but bear in mind I am by no means an authority.

The thermostat simply regulates flow of coolant to the radiator. The FSI thermostat is a bit special, having an electronic aspect but ignore that for now, but I expect it will not issue orders to anything, it simply gets on with its job.

The coolant sensor has four pins, two are for passing the temperature to the dash and two for ecu. It is not uncommon for one half to be faulty and in your case the dash feed is working yet the ecu feed may be bad and the ecu thinks the engine is cold and therefore does not instruct the radiator controller to get on with its job of running the radiator.

You can check by monitoring both coolant sensor outputs with VCDS, and if they agree I guess the the radiator controller is faulty and needs replacing. More likely the coolant sensor is faulty and without kit to monitor I would swap the temperature sensor, but on the FSI it is not easy, access is the problem.

Andy
 
It's been a year that I'm having the same issue as Chris explained in this thread, but I have an Audi Q3 2.0T Quattro 2013.

I don't know what else to replace

The only thing I have is a workaround. When both fans stop working, A/C compressors shutsoff and coolant temp hits 130 after 15/20 minutes. The workaround is open the fuse box on the left side of the engine, disconnect one of the Relays (there are two relays in that box) and reconnect it. After this I start the engine again and everything works just fine, both fans are running as spected. After one or two days the issue repeats.

Any help is welcome,

Luis
 
@rinox_rhcp
Not saying for sure but if your work around is to remove and refit a relay, then there is a good chance that relay has either burnt or arced contacts that may be keeping the contacts in the wrong position and the act of pulling it out either clears all the power in it or the shock breaks the contacts enough.

Have you had the vehicle scanned for fault codes?
 
rinox_rhcp said:
It's been a year that I'm having the same issue as Chris explained in this thread, but I have an Audi Q3 2.0T Quattro 2013.

I don't know what else to replace

The only thing I have is a workaround. When both fans stop working, A/C compressors shutsoff and coolant temp hits 130 after 15/20 minutes. The workaround is open the fuse box on the left side of the engine, disconnect one of the Relays (there are two relays in that box) and reconnect it. After this I start the engine again and everything works just fine, both fans are running as spected. After one or two days the issue repeats.

Any help is welcome,

Luis
Click to expand...
Buy an hour on Erwin, download the electrical schematic, and you be able to see how the fan is controlled. A scan might help too. Not VCDS Lite though, something like OBD Eleven, or VCDS proper.

erWin – Homepage not logged on

erwin.audi.com erwin.audi.com
Mac.
 
audifan said:
@rinox_rhcp
Not saying for sure but if your work around is to remove and refit a relay, then there is a good chance that relay has either burnt or arced contacts that may be keeping the contacts in the wrong position and the act of pulling it out either clears all the power in it or the shock breaks the contacts enough.

Have you had the vehicle scanned for fault codes?
Click to expand...
Yes, scans were done by several workshops, and faults founds had not lead to the real source of the problem.

The relay workaround doesn't work as in the beggining. Sometimes I disconnect and reconnect that relay and the issue persist when I turn back on the car.

One thing I'll try next week is buy the original battery from AUDI (it's an AGM battery), because now it has a standar battery (not AGM).

For the record, since issue appeared i've already replaced the FAN control module, the thermostat and water pump housing (including the temp sensor). Also a replaced both Relays (those mention in last post) and tested all fuses and other relays. Also I replaced the A/C coolant pressure sensor (G65).

Cheers,
Luis
 
The fan in the FSI is only controlled by the Fan Control Module. Which, in turn is controlled by the engine ECU.
Depending on the temperature data received by the ECU, and the Air Con being on, or off, the fan will run slow, run fast, or not run.
Are you sure it is not running, because it is not required to, at the time you checked it? Is the temperature gauge showing the engine as running hot, indication above 90C?
Mac.
Edit : Sorry, just re-read your first post, and I see is overheating. I'll have another think, and come back with something more helpful, 🤞
Mac.
 
Last edited:
You must log in or register to reply here.
Back
Top