Hi guys! 

 

I've been reading up on this as much as i can, but still dont know what to do so I need your help. 

I have a Octavia mk 2, 2005, 1.9tdi diesel, 1Z3, BKC engine. 182 000km. 

 

I fitted an extra ledbar to it the other day, using a relay. It is connected to the high beam light, not a separate switch. The minute im done with the wiring, and put the minus back on the battery, the coolant fan speeds up for half a second and then turns of again. I bearly noticed it, but did not put any thought to it. Took the car for a quick spin to make sure lights are working. I parked my car down the street from where i live and went to bed. Next morning, i get a message from a neighbor telling me my car is making a loud wierd noise, and has been doing it all night.. I go down to have a look, and yep, the cooling fan is running at full speed. It slows down after 10-15 seconds, go down to 0 rpm, and then full throttle again. Keeps going like that until i start the engine or take the minus pole off the battery. There are no yellow or red signals in the dashboard, nor any heating issues when driving. My diagnosis tool can't see any fault either. 

 

I took it to a workshop to have it diagnosed, and they say the cooling fan control unit is broken, and the fan needs to be changed. The price they wanted was ridiculous, so i got a new (used) fan. I changed it myself, and now its still starting up when i plug in the battery. It seems to be running at full speed now, without slowing down. Just constant full speed at the fans. When I turn the ignition on, it stops. Turn the ignition of, and it starts again.. I have no idea what to do, so im asking you for help.

 

One more thing, when i mounted the ledbar, the car was at a slight angle, so it looked like the coolant was low, so i topped it off a bit more. I drove it around for a few hours before stopping and realising it was above max. I took out a bit after changing the fans. 

I find it hard to belive the extra ledbar, connected to the high beam through a separate relay has anything to do with the cooling fan, but since it happened just after attaching it, i feel like mentioning it.

 

Does anyone have a good idea what I should do? I'm clueless.. 

Try disconnecting your modification bit by bit to see if resorting to original fixes things and check for any possible wiring disturbed during your mod, a car of that age will have wiring and/or connection issues especially one from a Scandinavian environment.

9 hours ago, MicMac said:

Try disconnecting your modification bit by bit to see if resorting to original fixes things and check for any possible wiring disturbed during your mod, a car of that age will have wiring and/or connection issues especially one from a Scandinavian environment.

Ive tried to disconect the relay from the powersupply. The cooling fan still runs at full power. However, when I did this, the ledbar cabel conected to the highbeam cabel was still conected.

Here is a diagram of how i conected the ledbar.

Right, so Ive disconected the ledbar relay from the car, both at the car battery and the headlight beam. Problem is still there.

 

About 30sek after engine and ignition is off, the cooling fan starts running at full speed again. Turn the ignition back on, and the cooling fan stops.

It may be helpful to know what area/wires were originally disturbed.

 

Just thinking out loud, possibly the connection to the coolant temperature sensor has gone low/high from a shorted/open connection or coincidentally it has failed.  If it has failed open circuit I would imagine the fan would go full on and possibly the instrument cluster gets a different source for engine temperature display, of course this is just my thoughts and not verified.

 

I'd check the wiring and connectors.

 

I'll see if I can find any wiring details and sensor test data and will get back to you.

Here are the ECU pinouts with expected values.

 

I have more info but I'll need to PM  you.

I'm rather unfamiliar with the type of fan control that I think your car has, but I did find a couple of snippets of info online last time I tried to understand it. A couple of posts of mine about halfway down this page: https://www.briskoda.net/forums/topic/470840-aircon-puzzle-intermittent-cold-output/

 

 

I think subsequent to that thread I did suggest to one owner of a car with this arrangement and a 'fan coming on when ignition switched off' problem that his fault might be the result of water ingress into the connector that goes to the fan control unit on the main fan, and I vaguely remember that something was found, so maybe worth a look in there?

 

Edited 5 October, 20205 yr by Wino

Thank you both for tips! Ill have a closer look as soon as I have time.

Just to cleryfy what I did when I mounted the ledbar: I used a relay shown in the picture above, the only cabel I cut was one withe cabel running next to sevral others in to the light box trough a connection point. I cut the withe cabel after testing that it was power to highbeam. It was cut, and i attatched the cabel coming from the ledbar. Cabels were twisted together and ironed together and then seald. I doubt that this has anything to do whit the cooling fan, but since it happend right after, it might...
 

Im not sure what the workshop did excactly, but i was told:

The following faults / defects found: Control unit / resistance of motor fan defective.
Subject to more errors.

What they wanted to do in the offer they gave me after:
Replace fan with resistor. Price: 2500 Nok
Fan from PDS. Price: 7000 Nok

Total price: 9950 Nok

This was a third party workshop.

There is a chance that the new fan I bought used, is also defective .. hard to know.

Okei, so this morning I was able to borrow a diagnosis tool, ill add them as photos. I deleted the codes and turned off the car. Cooling fan started up again. A few houers later i drove home. The car almost reached normal running temprature before i turned off the car. I opned the hood and was ready to disconnect the battery. I waited a moment too see if the cooling fan would start again as normal. But it did not. I waited another 30 minutes untill the engine was almost cold before i left. Still no fan running...

Im going back out again soon to dobbel check.

Here are the fault codes from the diagnosis tool:

Check fuse 24 in the E-box under the hood.

55 minutes ago, Wino said:

Check fuse 24 in the E-box under the hood.

 

Checked it. Nothing wrong there.