406 cooling fan - when should it run?

[tomthered]

Hope I can get an answer to this!

Should my 406 raditor cooling fan be running in this cold weather? Last week it seemed to run for quite a while after switching the engine off. This was after i had done a lot of driving. As an example I drive 15 mile to work. Its mainly motorway driving and speed is about 65 mph-70 mph. When I get to work I switch it off and it seems to run on for about 30 seconds then stop.

Is this right? Do I need to be looking at a faulty sensor or something. I also noticed that it seems to take ages for the heater cooler inside to get warm, although it does eventually. This is a marked difference between my Xantia, which is the same engine, is it not?

BTW its a 1.9TD 1999 model.

EDIT: tried to reply Steve but for some reason cannot see it so am editing this post.

Thanks for your reply Steve.

It takes me about 30 mins as I have 4 miles of A road driving before hitting the motorway then 4 miles of A rd driving into work. As far as I know the fan runs all the time. The temp gauge is about 70 degress or thereabouts. If its supposed to run on thats fine but it seems strange it takes so long to warm up! No I dont run the air con apart from once a week to maintain it.

[steve_earwig]

I'm not really sure myself but I'll ask a few questions in case it gives a better picture.

Is the fan running all the time the engine is running?
Do you have air con and is that going too?
What's the temp gauge doing?

AFAIK pugs do have some sort of post-cooling process but I wouldn't have thought it would be happening just now. At those speeds your journey to work shouldn't take much more than 15 minutes, which isn't really enough time for your engine to warm up properly, maybe this is why the heater isn't getting warm but doesn't explain the fan.

[mjb]

AFAIK pugs do have some sort of post-cooling process

I'm pretty sure it's only active after ignition's off if the temperature's over 100!

[old codger]

Only ever had 1 run on the 6-had a 405 for 4 years & only found out the fans did not work when stuck in traffic at the dartford crossing 1 summer.

that was terminal corrosion (bleddy stoopid place to put a relay )

[tomthered]

The temp is showing as about 75 so thats OK. Anyone got any suggestions on what it could be then.? There is definately water in the system!




EDIT where are the switch and relay located? might be worth changing both tried posting but must oly allow editing on same day rather than a fresh post

[steve_earwig]

I've been looking in the ever-so-useless Haynes, which shows a too basic diagram for a single fan and only the set up for twin fans with air con. If your fan is running all the time then either the switch is broke or the relay stuck. Probably not much help but I think, providing your cooling system is ok and free of air locks, you could probably just disconnect the whole lot for now anyway.

[tomthered]

Just read that the thermostat in the radiator might cause this to run all the time if its shut. Does anyone know if this is true or am I looking at the wrong thing?

[old codger]

Thermostat is under the diesel filter.If you mean the temp sensor just diconnect the wiring plug to test it.

[tomthered]

This is weird @Old Codger.

Did what you said and disconnected the left hand of the two sensors on the diesel filter unit. The one with a brown wire was corect according to the Haynes manual. We this turned off the fuel gauge so ran the car, no electric fans so I thought all sorted. Reconnected the wire and the remp goes up nicely as it should and no radiator cooling fan running all the time.

I assume the temp gauge controls the cooling fans and when they are needed. Could a faulty connection have caused them to run all the time. Would them running all the time be the cause of an increase in fuel used ?