Can't find cooling fan switch!

[Roops]

Haynes BOL still hasn't arrived and the cooling fan didn't run last night :-(

Can't find a switch--is it triggered from the ECU? No fuses blown in either place, so I will have to investigate the relays.

For now I have set an alarn in OBD2 program to remind me to turn the heater up full!

 

[Roops]

Forgot to say it's a 2001 on a 'Y' with 4 coil packs.

 

[Roops]

Well, reading elsewhere on the web it seems that the ECU triggers the fan relay, as I guessed. Or it should :-(

I have checked using OBD and the ECU reports 82 to 85 degrees C in normal running (with gauge reading normal as well), but if I let it rise to just over 100, the fan doesn't run. This would explain why the car boiled over climbing a hill with the wind behind me.

I wish I knew which relay controls the fan.

 

[frank]

on pre-facelifts the relay is next to the ecu relay by the battery (with "rad fan" written on the lid )

 

[SuperUno]

And you can tap in to the relay control wire, and add a switch to it and connect this to earth and then you can overide the ecu switch, this is what i did on the rally car (pre facelift)

 

[Roops]

Thanks for the help, chaps. I can't find any label on the relays, but when I get a day off I'll have a better look. And I live it in Cumbria, so it will probably be raining cats and dogs when I do

 

[Roops]

Frank: yes, fan relay is nearest the front and ECU relay is just behind. Shorting the switched terminals runs the fan, so I am getting there. Still no labels on or near the relays, though

 

[frank]

the coolant sensor is obviously working if its reading 100deg eh (the 2 wire one under the dizzy)
and the relay is probably triggered via earth from the ecu btw (and a constant live)

 

[Roops]

Yes, the dash gauge and the ECU (via OBD2) are both reading about the same so I trust them. The relays are different from my old 1999, so I can't swap with that. I might just swap the fan and ECU relays that are side by side, to see whether it fails to start

 

[Roops]

Grrr! The relay is fine and I tested it by swapping with the ECU relay. I checked the wiring for the coil of tbe relay with engine running and both wires are floating somewhere near ground. No 12V supply.

There are no blown or missing fuses in the 2 fuse boxes I found and everything else works normally.

The problem is that I don't know which wire should be 12V and which wire is switched ground from the ECU. If I patch in 12V to the wrong side, the ECU may fry the next time it tries to turn on the fan!

Grrr!

 

[frank]

The problem is that I don't know which wire should be 12V and which wire is switched ground from the ECU. If I patch in 12V to the wrong side, the ECU may fry the next time it tries to turn on the fan!

a test meter is a lot cheaper than an ecu !

 

[Roops]

I havr a meter. For the second time in my life it's a good one!

But what to test without a wiring diagram from the BOL? The best I can think of in my lunch break is a temporary wire with a 1/4" spade on it stuck into the relay coil connector, via a resistor (or the relay coil itself) and the test meter and onto a 12V live somewhere, then let it heat up until the fan should be running (95 °C?) and see whether the ECU pulls ot low and the meter shows current flow. If it doesn't, try the other terminal. If one works, I can patch the other one live for now. If neither works, either the ECU is faulty or the wire from it.

 

[frank]

the pdf manual has the coilpack wiring diag iirc

 

[Roops]

Doh! I didn't spot that. I'll download and have a look after work.

P.S. that may be the friendliest RTFM I have ever seen