Cooling fans not working

[steve_earwig]

Relays there seem to be immobiliser, headlamp wash timer, probably headlamps - I can't actually find a diagram for them though. As far as I know a relay is a relay, so long as it fits & has a high enough rating I can't see it mattering what you do.

The a/c relay is switched by the pressostat, I think you've found which one it is. It seems to get its power from the cooling low speed relay so if this isn't energised then it won't have any power either. So much for it being independent (btw the only way I can make sense out of this awful diagram is to copy it into Paintshop and rub out the bits I'm not following)

Having eliminated the temperature sensor by replacing it, now you need to know if the engine is actually overheating but the ecu isn't switching the fans on for some reason and the gauge is also faulty -or- if the overheat warning caused by something else. The second option gets my vote but I wouldn't feel comfortable about it until your fans actually start to work on their own.

[firemannotsam]

I think it is definatley getting hot as the top and bottom hose are very hot and it will expand some water out of the pressure cap.

It is not over heating driving I have to make it by sitting revving it for a while.

It has only went to warning light once sitting for an hour in a motorway jam but it last a little coolant.

If the preostat is faulty would that prevent the cooling fan powering up?

I will get some relays and swop and see. I may take out the temp sensor again and test the resisitence cold and hot.

Just don't want to melt my engine!!!
.

[firemannotsam]

If the relays in the box are lights etc then my original relays must be ok as they work fine in the box when I swopped.

I have had the ecu out for a new crankshaft pulley and belt relplacing how likely is it that it has a fault?

How likely is it that the pressostat if faulty can upset the cooling fan system?

Pain in the bum!!

Thanks for all the help so far.

[mickeybo]

(old school of thought) The 3 relays on fan control centre one 5 pin change over relay. Left fan relay (low speed) right fan relay (high speed) these relays
are earthed via terminal 2 on relay to cooling fan control unit. i would imagine you have a control unit fault or wiring. Just a few basic' checks. Remove 1 relay
at a time check relay base terminals no 3 must have 12v's ignition off or on Switch ignition on must have 12v's applies to all 3 relays when relay is removed
check terminals 1 & 2 for resistance using multimeterreading should be approx 70 ish ohms. If checks above are ok i would relay again wrap a bit of wiring
around terminal 2 on relay replace relay with ignition on touch other end wire to a earth relay should activate Hth Regards Mickeybo

[lozz]

What is the heater like is it blowing out Hot
when it over heats or as you describe Expansion overflows.. does it blow out cold air then?,

[firemannotsam]

No heater is fine.

Tempted to just fit a sensor switch into the bottom hose and switch the fan from there as it will prob cost less than switching parts till I find what's wrong and if its an ecu prob it will be expensive!

£30 would fix it with a seperate sensor switch to feed the fan direct.

Just want it fixed to I can not worry about it.

[splitpin]

Have you sorted your fan problem yet?
I had a similar situation on my 1999 2.0 HDi 110 Exec where the gauge read 90ºC but the stop light kept flashing and beeping and "Engine TempToo Hot" displayed on MFD.
I checked under the hood, sorry bonnet (thats what happens when you do an apprenticeship with an US car building company in Essex), and the engine was definitely not over heating.
If I switched off the A/C, it went off.
I found that both resistors next to the fan had gone open circuit.
I made a temporary permanent repair and all is now good.
Just got to replace the leaking pressostat and A/C relay in the bsi then the A/C should work again.
Graham.

[firemannotsam]

Hi I checked the relays and the resistors and the sensor and all were working fine so I have assumed its an ECU fault or a broken wire on its way from the ECU that is the problem.

I have installed a temp sensor in the radiator hose and that now switches the fan on and off when the temp gets hot enough.
It was a cheaper fix than replacing lots of expensive bits and I even wired in a light on the dash to indicate when the fan comes on at each speed to give me confidence it is working. Total cost about 50quid which it would have cost me a lot more to take it to a garage or auto electrician. The car is getting on a bit and not worth the expense.

Not sure why the sysytem needed to be so complicated in the first place!

[Busman]

I had this exact problem. It turned out to be the two thermal resistors next to the fan above the black relay box. They measure the air temp in the fan housing. They cost about £6 each from pug.
However, your fix sounds a truely impressive bit of improvisation.
Why is it this complicated? I supose its to keep the temp more closley regulated. The first electric fan car I had just had a sensor in the outlet side of the rad. Just the one. Temp to high, on came the fan. If it went wrong, you pulled of the plug and the fan ran all the time.
It's called progress, so they say.