cooling fan

[welshviking]

Having only had this 406 3 weeks i have not got round to checking everything yet so today i had the car ticking over and then i noticed the RED STOP light flashing and the temp gauge very high, when i looked through the grill i could see the fan was not operating. Well off came the grill (snapped one of the three stupid clips ) and 1st surprise was there was only 1 fan, i remember on my Citreon Xantia hdi 110bhp there was 2, anyway when i tried turning the fan by hand it was solid. I sprayed lots of wd40 behind the fan and it started moving so i turned it one way then the other and in the end it was moving freely. Now the fan operates when the air con is on and also when auto air con is on it also operates sometimes when the car is just ticking over (no air con on). I have not taken the temp up to full yet to see if it engages when needed when car is hot. I am guessing it is some sort of viscous fan and not an electric one (may be completely wrong though !!!) . Does anyone know what the correct operating procedure is for this type of fan as i want to keep my eye on it to make sure it is now working as it should be....Thanks Colin

[mjb]

The fan should be electric, but I'm afraid I have no experience of the single-fan system.

The dual-fan arrangement runs them in series for low speed operation and in parallel for high speed "crud I'm overheating" operation, but will happily survive with only one fan operating (full speed or nothing)

If I were you I'd be happy it works and probably start watching out on ebay for a cheap replacement single-fan unit (the dual fan jobbies are designed to go around different radiators, and may be electrically incompatible with your car although you could probably hack it to work if you were so inclined )

[bigpug]

hi mjb i have a similar prob but my fans dont cut in at all and its the two fan version any help most appreciated

[mjb]

hi mjb i have a similar prob but my fans dont cut in at all and its the two fan version any help most appreciated

Check:

1. The fan blades spin freely when you prod them by hand (ignition OFF and be careful just in case it decides to power them up - they'll slice through your hand nicely)
2. The engine bay fuses (a pair of yellow 30A jobbies iirc)
3. Electrical connections
4. The relays
5. The fan motors (give 'em 12v)

If still nothing, replace:
1. The ECU coolant temperature sensor
2. The Bitron ECU

If you've still got no fans I'd be wondering about bosted wiring

[bigpug]

cheers mjb ive tried rotating the fans and they both move freely, i think all the relays work as the coil pulls in on them all and the normally open/ closed contacts work when coil is energised engine bay fuses are both ok. what is the easiest way to get 12v onto the fans without taking all the bumper etc off? cheers

[mjb]

are there connectors from the fans going into where the relays are?

if not i'd take a relay out, work out which pin is the 12v to the fan, which is the 12v to the engine fusebox, and with some thick wire either bridge the pins or hook the fan 12v up to the battery momentarily to see if the fan moves.

might actually just be easier to measure resistance to earth through the pins. by my reckoning the fan's 12v should be around 0.5 ohms since they use a 30A fuse I'll guess at about 24A current per fan. V=IR, 12=24xR, R=12/24=0.5 ohms. If you get nothing then the fan motor's likely shot.

[Doggy]

Actual resistance is often much lower than Ohm's law suggests - as the current is only 'pushed' around by the difference between applied voltage and the back EMF the motor 'generates' as it turns. A factor of 5 times less isn't unusual e.g. 200kW dc shunt motor, 460V 480A armature, dc resistance 0.2 ohms.

[mjb]

I did say "around" 0.5Ω and based it on a pure guess at the fans using 24A (given the fuse and the handy fact it divides by 12 ). I'd probably guess anywhere between 0.05Ω and 2Ω would be correct. Something like 0.0001Ω or 10KΩ would probably indicate a bosted motor

(guess who figured out how to do the ohm symbol? )

[steve_earwig]

Ωygod!

The fan feed should be marked "87" on the relays and the supply "30". Bridge those two (I can't remember which relay is which now but with them all unplugged it won't be an issue anyway, just try them all)

[Doggy]

(guess who figured out how to do the ohm symbol? )

Impressive - I was feeling smug at finding how to do the €

[steve_earwig]

I've got a button for that on€

[teamster1975]

Ωygod!

Silly @rse