Cooling Fans

[SimonKD]

Hi All

The saga continues with my cooling fans and I have a few more questions to try and sort it out once and for all.

Firstly I'm led to believe that fan No.1 should be on all the time if the aircon is on, is this correct?

Which fan should come on first as engine temperature rises, n/s or o/s, my o/s fan seems to have smaller blades than the n/s one?

My No.1 fan is not working at all at the moment so the second fan is doing all the cooling hence the car is running hotter than normal.

I've had the large cover behind the air filter box off and jumped 12V to each fan in turn and the both work fine.The plug and sockets on each fan are clean and dry.

I've also swapped the yellow relays over in the fusebox for fan No.1 & fan No.2 but problem remains.

Could it be the temperature sensor that tells the ECU how hot things are that is faulty or even the ECU itself. I think not because the second fan is coming on?

Where is this temperature sensor located and is it easy to change?

Once again any help greatly appreciated

Regards
Simon

[morebeanz]

Simon

I agree with your logic about the sensor, which really only leaves the physical wiring to the first fan. Have you checked for any drops across the wiring that's in use? Are you sure you have a sound circuit using the wires for number one fan?

[Extra 300 Driver]

SimonKD said:

Firstly I'm led to believe that fan No.1 should be on all the time if the aircon is on, is this correct?

Regards
Simon

Mine didnt, looking forward the left one came on about 92 the right about 99, aircon or not, oh and my air con was really good too!

[SimonSparrow]

Apparently removing the plug to the temperate sensor will cause the ECU to power up both fans at all times as a precaution. Might help if you're trying to troubleshoot. I think this will turn on the MiL light too, so you might want your laptop handy to reset any fault codes.

[SlvrCrb]

SimonKD said:

Hi All

Where is this temperature sensor located and is it easy to change

Looking at the car face-on, it's under & to the right of the washer bottle (Assuming your reservoir is front & centre) and is screwed into the top of the rear swan neck pipe. Remove the plastic F1 wing and you'll see where the spirally (sp?) sensor wire from the mech guage comes from the bulkhead on the left and is routed down the front if the block and is screwed in to the swan neck. Follow the swan neck along to the right about 6 inches or so and the ECU temp sensor is there. Unplug the sensor wire and unscrew. You can replace this without draining the cooling system but be bl88dy quick and have a spare finger to jam in the hole until you screw the new one in..!!

[jbvipercerb]

The "big" fan on mine stopped working while I was tuning the engine, so I saw it straight away, one minute it was working the next it wasn't. all it was, was a bad connection in the plug just underneath the fan, a good clean up and sealing with vasaline its been right as rain. Now I've said that......

[marcus1970]

SimonKD said:

Hi All

The saga continues with my cooling fans and I have a few more questions to try and sort it out once and for all.

Firstly I'm led to believe that fan No.1 should be on all the time if the aircon is on, is this correct?

Which fan should come on first as engine temperature rises, n/s or o/s, my o/s fan seems to have smaller blades than the n/s one?

My No.1 fan is not working at all at the moment so the second fan is doing all the cooling hence the car is running hotter than normal.

I've had the large cover behind the air filter box off and jumped 12V to each fan in turn and the both work fine.The plug and sockets on each fan are clean and dry.

I've also swapped the yellow relays over in the fusebox for fan No.1 & fan No.2 but problem remains.

Could it be the temperature sensor that tells the ECU how hot things are that is faulty or even the ECU itself. I think not because the second fan is coming on?

Where is this temperature sensor located and is it easy to change?

Once again any help greatly appreciated

Regards
Simon

No1 fan shouldn't be on unless the water temp is 92+, regardless of air con.

n/s fan should come on first (fan number 1)

number 1 fan should come on if you unplug the water temp sensor (and number 2).

Water temp sensor is on the n/s top of the coolant rails near to the n/s fan and closest to the front n/s wheel.

If you plug the laptop in, the water temperature will be displayed. As the temp coincides with the fan settings the ecu will display fan Number ? on. Until then the fan will be displayed as off. Fan 1 should come on at around 92 fan 2 at around 96/97.

Temp sensor is easy to replace and costs around £10. However be careful if your water rails look corroded as you may end up replacing these as well as the nut/thread can seize up due to corrosion etc.



MB

Edited by marcus1970 on Wednesday 13th June 16:06

[SimonKD]

Thanks for all the info people, I think it's sorted.

The plug and socket terminals on the temperature sender were covered in green crap this was causing a faulty temperature signal being sent to the ECU.

Cleaned all terminals and sprayed with WD40 fans now both operate properly coming on at 95c and 100c (on the dash gauge that is)

If I'd had the new type lead I could have plugged the laptop in and seen the dodgy temperature reading straight away and saved time in diagnosis.

Does anyone know if the new type plugs (my late type ECU has a flylead external to connect the laptop to) can be purchased from RS or the like so I can make a lead up as I think £40+ is a little expensive for a serial lead?

I would need a pinout drawing for the new type lead as well.

Thanks again for all the help

Happy again
Simon.