14 replies to this topic

[mk22door]

Hi,

 

We think the relay for the fan might have gone?

 

Where is it located?

 

R reg '97 MPi

 

Cheers

[FlyingScot]

It's in FAQ's http://www.theminifo...elay-locations/

FS

[mk22door]

Thanks, that's a great link, very handy.

 

 

...but now we have power all the time at the relay at two points, if you earth the relay the fan is constantly on and doesn't go off regardless of the ignition being on or off.

 

[mk22door]

Just found this which is helping us think it through..

 

http://www.cantymini...al_cdxn990e.pdf

[71bay]

No help I know but my fan comes on with the ignition and is on all the time !

[FlyingScot]

Yep you need to check the wiring for chaffing. Temp sensor wiring loom section (there was a service upgrade as the wiring was too short). Fan controlled by MEMS on MPi not thermo switch as SPi.

FS

[mk22door]

Well, that can't be right surely?

 

It'll burn out eventually, like the original one here that has just been replaced.

 

We've done new expansion tank, new water pump, new thermostat, new coolant temperature sensor (presuming that is the one in the sandwich plate/thermostat?) New radiator, new fan, no pressurised pipes - all cleaned/flushed out with gentle hosepipe and back filled the coolant system to make sure we had no airlocks.

[mk22door]

Yep you need to check the wiring for chaffing. Temp sensor wiring loom section (there was a service upgrade as the wiring was too short). Fan controlled by MEMS on MPi not thermo switch as SPi.

FS

 

The telesales bloke at minispares told me the sensor was both coolant sensor for the fan to be switched on and for the temperature gauge in the dash.

 

Anyway, do you mean check that section of the loom for chaffing or that there is a Temp sensor wiring loom section here on the forum that I need to read to enlighten me?

 

Going to check if now that the engine is cool, that the fan still comes to life by creating ground from the relay...

 

If the fan is still coming on then it may be that it's arcing out somewhere???

[FlyingScot]

Yes I mean the wiring rubbing, the sensor is in the thermostat housing and sends the signal to the MEMS ECU, this controls the fan via the relay. Common faults are damaged wiring and a bad connection to the sensor.
I don't recommend creating new connections especially earths on items controlled by MEMS....

If MEMS doesn't get the right reading from the ECT (engine coolant temperature) sensor it turns on the fan.....
Check wiring, clean up brown socket and contacts on sensor.
Link to sensor (which also mentions loom change section - original was too short and led to chafing)
http://www.minispare...er/GTR206.aspx?

FS

Edited by FlyingScot, 18 May 2016 - 10:55 PM.

[mk22door]

Fan still comes on with earth added.

 

Some rubbing has occured but cannot find anything broken at the moment.

 

Can we not just use the sensor in the thermostat sandwich block in situ to make our own fan cooling kit? You know add in our own loom with in line fuse and it's own relay? Just like when you buy a kit off the shelf.

 

Thanks for the help.

[FlyingScot]

Don't add an earth... MEMS internally earths the relay coil to switch it on (see 20.2 on the wiring diagram). Also don't put a meter across MEMS to test for the earth...
Do trace the power feed (purple) to the switch side of the relay and trace to the fan. Also check coil side of relay, are you sure it isn't stuck on?
The sensor isn't a switch - it's a NTC measuring device powered by MEMS and the MEMS ECU determines when the fan should come on (>98C from memory).
Step by step my friend and you will find the issue, please take care around adding extra wiring around things controlled by MEMS as I wrote above - if you knacker the control voltage or driver circuits you will need an ECU repair £££

FS

[mk22door]

The relay and wiring to it is all working fine, tested with 12v tester (illuminated slotted screwdriver/croc clip) to the fan multiplug. Swapped the relay itself for headlights/directional indicator relay - so we know that is all good. Already been all over with the multi meter im afraid!

 

Cut out the plug connection and a load of wire to the sensor and fitted temporary wire straight from sensor to just before the wire dissapears into the loom, still no fan until you dissconnect one side and this activates the fan - which stops the coolant from overheating in the bottle but the fan stays on until you turn off the engine.. then doesnt come back on.

[FlyingScot]

Can you measure the ECT sensor in ohms?
Disconnecting the sensor will cause the fan to run as MEMS sees a fault state and runs the fan to prevent overheating.

FS

[mk22door]

At the minute it reads nothing but the engine is cold as bacon butties forced a lunch break.

 

I like the temporary solutuion of fooling it into life, might put in a switch to the dash to make the fan come on if needed whilst I look for a good used loom or something?

 

What should the ECT measure in ohms?

 

Cheers

[FlyingScot]

It's it reads 0 ohms it's knackered.... Because that implies to MEMS it's over 110C
At 20C it should read 2200-2800 ohms at 10C it's 4000 ohms so dependent on the "cold" engine temp it should be something around there.

FS