Fans not workiing

[dlewis]

As the search function no longer works, can someone tell me about the fan circuit logic as fans are not triggering at all.

There are two switches in the block, does one control the gauge and one feed the ECU.

Fuses are OK and relays swapped with spares.

The switch towards the front has a damaged cable (so will be replaced)but shorting the lead out did not have any effect.

Anyone been there?

Dave

[nrick]

Hi Dave

No expert, but I have one fan down.

The first fan comes on at 93-95 deg (or ac), and then if the temp hits 98deg (ish) then the other switches in. Looking at mine the cable was damaged, looks like it just hangs there and got chewed by the fan. The guys on here will tell you to look at the plugs as they tend to corrode.

That is all I can suggest, but I am a newbie so don't shoot me down

Neill

[dlewis]

Thanks Neill

Looking at the way the front switch cable waves in the wind with the weight of the connector is a certain fatigue failure.

Maybe we all need to check this as the part is not cheap and the consequences could be expensive.

I am hoping that is all that is wrong but would like to hear if I need to change the other, albeit cheaper, temp switch.
Dave

[nrick]

I would look at the white connectors as well as a known fault.

N

[dlewis]

Yes, I cleaned them up while the bonnet was off.
Dave

[dvs_dave]

Assuming you've checked the fuses?
The ECU is set up to fail safe so that if a bad temperature sender signal is detected it automatically switches on the fans. Have you tried just unplugging the senders to see if the fans come on? Failing that, check the 2 fan relays (the yellow ones) by taking them out and swapping them over.

[drivingfroggy]

When mine stopped working, it was corrosion in the spade connector for the sensor in the block under the airbox. Cleaned it up and squeezed it closed a bit, job done.

[dlewis]

Dave

Yes, as OP, fuses OK.

Did fire up ignition with both sensors diconnected but nothing.
Phil

Terminals were cleaned.

Dave

[onny]

Water temp sensor is the likely problem if not fuse/relay.

[blueg33]

dlewis said:

Dave

Yes, as OP, fuses OK.

Did fire up ignition with both sensors diconnected but nothing.
Phil

Terminals were cleaned.

Dave

I may be wrong, but doesnt the sensor complete the circuit, so disconnecting them won't be enough, you would need to short across them

[NCE 61]

blueg33 said:

dlewis said:

Dave

Yes, as OP, fuses OK.

Did fire up ignition with both sensors diconnected but nothing.
Phil

Terminals were cleaned.

Dave

I may be wrong, but doesnt the sensor complete the circuit, so disconnecting them won't be enough, you would need to short across them

It's not like the switch on the RV8 where you can short out the connections on the temperature switch. If disconnecting the rear temperature sensor does not bring on the fans i.e gives a default reading of 95 Deg.C at the ECU, then as you have already eliminated the fuses and relays it could be the electrical connectors to the fans.

[nrick]

As above, my understanding is ecu controls fans through the relays , any faults and it should default to 95 and switch one fan on. It is an intelligent system, not like the old hardwired versions. Other option is to hardwire fans in to check fans.

[dlewis]

Well armed with a digi meter I found lives all present and correct.

Looking like the ecu ground is not working to drive pin 85 on the relays.

Have cleaned multiplug.

Can someone tell me where the ecu is - either tucked up in the dash or in the side panel, certainly looks tight in there.

Dave

[nelly1]

The ECU is on the bulkhead behind the pedals - held in with a 'U' bracket - tight is an understatement!

Depending on which year car you have, the ECU plug could look like this:



The ECU drives the two fan relays via this connector:



ECU pin 6 drives fan 1 via pin 6 of the 24 way.
ECU pin 41 drives fan 2 via pin 16 of the 24 way.

If you have the later type ECU with 3 smaller plugs you need the black plug (as oppose to the grey or brown ones) and pins 4F (fan 1) and 2F (fan 2).

[dlewis]

cheers Neil

I will take a look at ECU and will go back to the 24 pin block now I know the pins.

Its a 2001 model.

Dave

[dlewis]

They are now!

Not entirely sure but a direct feed to the fans to run them up for a while, new temp sensors, reseat all fuses and relays, cleaning all loom connectors blocks from fans back to ECU with a reboot of the pod has done the trick.

Dave

[nelly1]

Whatever it was exactly doesn't matter now.

If it happens again you know this bit of the puzzle inside out now.

Easy when you break it down isn't it?