Yet another thread on cooling fan

[DaPol]

I have a (somewhat tatty) facelift CDTI with a fan problem (yeah yeah - I know - me and everybody else).

Testing with the Trinary switch trick shows me that high speed works fine.

I took the front bumper off (yay for new paint scrapes due to klutzing) and found the infamous silver resistor, so - I have a 2 speed fan.

Lacking a gold resistor, I cut the silver resistor out of circuit and jumpered the two loose ends together - if I understand correctly this should allow my fan to run, albeit at full speed when low is selected?

I then start the engine and put the AC into "demist" mode - the fan doesn't run.

So, most likely, what am I looking at having to replace? The fan motor, the control box or whichwhat? Anybody got any ideas?

Given my car appears to have been sprayed in blue cheese rather than paint (seriously - softest paint I've ever met) I'd rather not be taking the front on and off more often than I can avoid, so if I can do it once and fix this then it'd be great, so if anybody has any idea what I need to replace I'd be grateful.

I *could* just buy one of Jules' fan+controller kits, but if I don't have to spend a few hundred quid, I'd rather not.

[RodgerD]

I have a (somewhat tatty) facelift CDTI with a fan problem (yeah yeah - I know - me and everybody else).

Testing with the Trinary switch trick shows me that high speed works fine.

I took the front bumper off (yay for new paint scrapes due to klutzing) and found the infamous silver resistor, so - I have a 2 speed fan.

Lacking a gold resistor, I cut the silver resistor out of circuit and jumpered the two loose ends together - if I understand correctly this should allow my fan to run, albeit at full speed when low is selected?

I then start the engine and put the AC into "demist" mode - the fan doesn't run.

So, most likely, what am I looking at having to replace? The fan motor, the control box or whichwhat? Anybody got any ideas?

Given my car appears to have been sprayed in blue cheese rather than paint (seriously - softest paint I've ever met) I'd rather not be taking the front on and off more often than I can avoid, so if I can do it once and fix this then it'd be great, so if anybody has any idea what I need to replace I'd be grateful.

I *could* just buy one of Jules' fan+controller kits, but if I don't have to spend a few hundred quid, I'd rather not.

These motors are one speed with the resistor throttling back the revs on a parallel circuit. I'd say you have a stuck open low speed relay or defective relay control.

Sadly the relays are housed in a box next to the fan, which means removing the bumper, slam panel etc.

[DaPol]

OK - so, best case is a gold resistor and ...maybe being able to fix the control box - does anybody know if the relays used in the box on a CDTi are available/common and replacable?

[RodgerD]

OK - so, best case is a gold resistor and ...maybe being able to fix the control box - does anybody know if the relays used in the box on a CDTi are available/common and replacable?

Commercially available relays, traders on the forum sell them, or you could look in the internet. Details are on the relay housing. Take care when removing the relay from the control board.

[SD1too]

... I cut the silver resistor out of circuit and jumpered the two loose ends together ... and put the AC into "demist" mode - the fan doesn't run.
Hello Paul,

The diesel circuit can throw up some surprises. This might sound like a strange question but is your air conditioning in working order? In other words, does the compressor engage when you select 'Auto' or windscreen demist? I ask because evidence collected over the years suggests that if the air conditioning compressor does not engage, the fan will not run either, but only on diesel cars.

Please report back Paul.

Simon :}

[DaPol]

The AC compressor does actually engage - get the *clunk* off the clutch engaging, and the engine note drops as the load increases, and if I'm running into a sufficient headwind I even get some cooling effect from the vents with the AC set on recirc.

I'd have to say that it does work.

[SD1too]

OK Paul, that's good. You can check the faulty relay theory yourself reasonably easily and it won't cost you a bean.

Take the lid off your control box. You should see three relays in there, even though you have a 2 speed system. The small relay in the centre is responsible for the low speed. Swap it with the other small relay (which is redundant) and try the demist test again.

Simon

[Rev Jules]

OK Paul, that's good. You can check the faulty relay theory yourself reasonably easily and it won't cost you a bean.

Take the lid off your control box. You should see three relays in there, even though you have a 2 speed system. The small relay in the centre is responsible for the low speed. Swap it with the other small relay (which is redundant) and try the demist test again.

Simon


Sorry to cut in on this one, just replaced the Silver one with a Gold one the hard way through the front grill, but still the fan is pulsing on and off
it is quite cold coming through the vents.#

Julien

[T-Cut]

- - - -still the fan is pulsing on and off


Slow speed relay issue? Try replacing it with a known good/new one. They're standard issue i believe.

TC

[bigdaddystew]

Hi..just passing on my limited experience for what its worth with the cooling fan on my 2004 cdti..replaced resistor with new gold one a couple of weeks ago..fan would not work..thought my aircon was ok..took it to have aircon checked..the guy suggested i had it done..it turned out the system was lacking the optimal amount of refridgerant ..had it done {£30}..fan now working when aircon is used and when demist is used.. Have ordered new relays from Jules to have as a backup..regards stewart

[rovertone]

I have just fitted a gold resistor, the fan runs at slow speed on 'demist' test and steps up to high speed when I 'short' trinary switch. This is with the aircon degassed (but that's another story!). I seem to remember (and hope) this is correct on a diesel, the compressor clutch doesn't engage because of nil pressure.

[DaPol]

OK - tonight I bit the bullet and went to town on the front of the car.

Oh how I hate the front of these cars.

Anyhoo, several rusted to rusty thing bolts later (about a half of them), discovering overspray on one of my headlamp units which ties in with the suspicion somebody's resprayed bits of the car and manymuchlots rewiring, the end game is:

No idea whether or not the silver resistor was knackered - I'd cut it out of circuit before taking the front fully off.

Gold resistor fitted.

No fan.

Follow the wires and discover that one of them had frayed through where it exits the concertina tubing - corroded away and all that was there was a whisker of insulation - trim back to beyond that, resplice the resistor at that point and cue a nice working fan at low speed :D

Then look around some more.

The wiring into the temperature sensor was in similar (poor) state, so butt splice that.

While the front was off, replace the rather pathetic Fiamm single horn with a nice set of Ring hi/lows from Halfwits (decent clone of Stebel Magnum from what I can tell) and I now have a horn which is rather less apologetic than the one previously on it.

Naturally when refitting the front end I managed to end up with one side lower than the other, but I really can't be bothered trying to fix that just now - it's not hugely offline.

Next up is figuring out what to do about the paintwork - it's apparently Odyssey Blue, but it's also the worst paintjob I've ever had on a car - there are large chunks of the lacquer coat missing and the stuff scratches like nothing I've ever seen.

[SD1too]

Follow the wires and discover that one of them had frayed through where it exits the concertina tubing - corroded away and all that was there was a whisker of insulation - trim back to beyond that, resplice the resistor at that point and cue a nice working fan at low speed :D
Thanks for letting us know the outcome Paul. Not an easy fault to predict, but it's interesting to note that it wasn't the frequently accused relay.

Simon