Cooling fans not working

[firemannotsam]

Hi guys looking for some help.

I have a 1999 2.0 HDI 110.

The other day I was sitting in traffic and I got the "engine coolant temp too high" warning.

It seems the cooling fan is not working.
I thought the temp sensor so replaced that, still not working.
I dont want to just keep replacing stuff at cost.
The fan work as if I remove the plug from the coolant sensor the fan comes on full speed but goes off when I put it back on.
If I connect pins 3 & 5 on the top green relay in the fan housing the fan comes on at low speed, if I also do the same on the lower relay I get the middle speed and the fast speed if I pull the sensor so I am happy the fan works fine.

Does this mean the resistors are fine too?
I have cleaned all connections on the relays no difference, I have swoppped the relays with some other identical ones from another lot by the battery but still no difference.
I will go out in the morning and start trying to test if the relay is getting power to the circuit when the car warms up.

The car has aircon but I keep it turned off as it needs a leak fixing, when I turn it on the fan does not turn on low speed but I would expect that the aircon wont work as its out of gas.

Not sure how to test the relays and resisors?

I have looked for the the bitron relay under the f/n/s arch liner and cant find one??? does this mean mine is ecu controlled?
Or am I looking in the wrong place and pics of where the bitron is?

I know lots of questions but any help would be appreciated.

Thanks.

[steve_earwig]

Hi there, welcome

There is no "Bitron" control box, it's all run by the engine ecu. Nothing will happen with the air con because there's not enough pressure to work the pressostat. All the rest of it sounds ok, even if the low speed relay was up the swanny you'd still getting the high speed going, so perhaps your coolant temperature sensor is either sitting in an airlock so it doesn't know the engine is hot, or it's dead.

[jamjar1383]

i had a similer prob on my last hdi turned out the was a wire under the battery tray that had broken so i patched it and it worked fine

[firemannotsam]

Thanks for replies guys, it is a new sensor so should be fine and guage reads ok.
Will bleed the coolant out of the top of the thermostat and check the wiring under the battery.
Will try to see if there is current to the relays when the engine gets hot.
I did replace the heater matrix a few months ago so maybe I did not bleed it well?

Which wire under the battery was broke? Was it from the fuse box? Did you have to take the battery box out?

The relays and resistors should be ok then?

Thanks again

[steve_earwig]

Dammit, my turn not to read the OP properly. And I spent ages squinting at the wiring diagram too

I'm still thinking if you pulled the connector off the sensor and the fans went on full then the sensor isn't telling the ecu the engine's hot.

[jamjar1383]

iirc it was a gray wire and i had to take out the battery tray ou to get at it, but if its the same thing u should be able to spot it

[steve_earwig]

Just by the by, I had a squint on Autodata and it says in the common problems and fixes bits that if you get a temperature warning light but the gauge reads normal then the relays need replacing. Not sure if that's what you actually had, it's still a bit nippy these days so I don't think the fans would be doing much anyway.

[firemannotsam]

Thanks guys, the guage reads 90 when the coolant temp warining comes on.
Where does the ECU get the info for this warning?
If all the info comes from the temp sensor then it should be ok?
I will check wires under battery box and bleed the system on the screw on the thermostat housing but if it was in an airlock would it not set off the temp to high warining at all.
Seems like a very overcomplicated system.
Are there any other relays that supply the fans? Under the enginge fusebox?
If I sit with revs on the car parked up for a bit I can get the warning to com on but the temp guage still sits about 90.
To test the relays I can supply pwer to the coil circuit and listen for a click and then see if a circuit has been made between pins 3 and 5? (The ones I connect to make the fans run ?)?

Hate electrics not my thing.
There are a bunch of relays in a black box by the battery box that are the same as the ones in the fan can I use them to test or will removing them affect the system?

Thanks again!
Looks like I will have A fun morning.

[firemannotsam]

Forgot to ask, if the relays are a problem can I use a basic 5 pin changeover relay or does it have to be the original type with a resistor as the piccy on the relays suggests?

Thanks

[steve_earwig]

I got a similar warning when my fans packed up on my D8, I guess it knows somehow

It just occurred to me in the shower, being 1999 it's not clear if your car's a late D8, an early D9 or a mixture of the two, if it's "fans" it must be a late D8 but the resistors make it an early D9

How many fans you got?

90 degrees doesn't sound like it's overheating. As far as I know there's just the three relays (on later cars they're by the engine fuse box).

I'm pretty sure there's more than one temp sensor but I can't find a second one on either of the diagrams - you must have the one that runs the fan(s) there, if you disconnect it what does the temperature gauge do?

At least one of the relays changes over (probably the blue one) so best to check them both ways if they have 5 pins.

[firemannotsam]

Hi its a single fan with 3 relays in the box by the fan green one then blue and then green again.

The top green one if I take out the relay and make the circuit it runs on the slowest speed, the blue one in the middle is the one that seems to operate the highest speed and if I remove both green relays then make the circuit on both the green ones then I get the middle speed.

I can only find one temp sensor on the alloy thermo housing (green plug) which I have replaced.

If I remove this connector then fan runs through high speed blue relay even if I take both green relays out.

I do have a box by the battery which has 4 relays and 3 40A fuses but not sure this has anything to do with Fan.

I am about to go test the relays and see if there is power to the relays when it does get hot.

I think sensor must be working cos temp guage works fine and warning comes on, If I pull the plug it then rises towards red and fans come on.

Thanks for input.

[steve_earwig]

So there is only one sensor, that's neat. There used to be 3...

I've just been squinting at the wiring diagram again, what you're doing by shorting both relays is running the fan through both resistors in parallel to get a "medium speed", one resistor and one relay are only there to run the fan at low speed for the air con and are controlled by the air con's "pressostat" (pressure/temperature switch) independent of the engine's cooling system. If you car didn't have air con it would only have 2 relays and one resistor.

Not that this helps you much as I still can't tell you which relay is which, except that the blue one is higher current than the other two. This runs the fan at full speed as you've found. None of them change over now, all three are just there to make circuits.

I can only think to check the relays out as you're doing. Presumably this false overheat warning is coming from the engine ecu because it's seeing a fault somewhere on the cooling circuit.

[firemannotsam]

Its annoying me now!

Swopped the two green relays with ones from the black box by the battery case.
No difference.

What do the relays in that box do?

Ran car up to temprature and got the warning coming on, no power supplied to the lower green relay!
Either the coil circuit or main circuit.

Can only get the medium speed to work if I bypass both green relays, should the bottom one work independant?
Pissing down so put it back together.

The sensor must be working if I get the warning and its new so that can be at fault!
Are there other relays that control this?
I know its not really a prob as car rarely sits in traffic but when it does it will expand some water out of the expansion tank and I have to top it up.

Don't fancy paying a garage loads to look at it!

Can I use any basic 5 pin relay as long as its rated to at least as many amps? If so I will just buy a load and swop all the relays. The proper ones are a bit pricey if I don't need them!

[lozz]

this is confusing
My 2.0 hdi will sit at 90 all day even in traffic and with the weather being abit coldish ive not heard the fans cut in yet,
im sure thatl change in summer tho,

Yours must have an air/lock mate or the expansion cap couid be fubard

[firemannotsam]

Hi, not sure how an airlock would cause the warining to come on?

It does not get hot in normal use to get it to put the warning on I have to sit with some revs on for a while or in traffice for a vary long time!

Just concerned at the possibilty of it damaging due to overheating.

It was loosing a bit of coolant due to expansion when hot.

Cap being FUBAR would not cause temp warning.

Confusing!