Cooling Fan Problem - Confirmation Of My Diagnosis

[joni 0]

Hi All,

 

There's loads of useful stuff out there about cooling fan problems which i've read and i've come to the following conclusion about my 205 problem which i just wanted a bit of confirmation about given that i have a rally this weekend and little time to fix the problem....

 

Problem - My fan doesn't come on when the engine is (too) hot. I overheated in a traffic jam yesterday.

 

Suspected problem cause - Temperature sensor mounted in radiator.

 

Reasons - I have a three pin sensor in my rad. There is 12.5v live going to it, if i bridge to the other two terminals they both work i.e. slow and fast speed.

 

Sound right or am i missing something?

[ade 4wd 11]

Yes, your temp sensor is faulty. Replace it and all should be well.

[M@tt 77]

have you tried cleaning up the sensor terminals first, they are known to get a bit furry, worth a try before splashing out on a new one

[joni 0]

Yes, your temp sensor is faulty. Replace it and all should be well.

 

Thanks!

Can anyone confirm the part number for this temp sensor mounted in the radiator? Its 3 pin, all the pins are in line with each other (like this - - - ) and the plastic surrounding the pins is blue.

Edited September 30, 2010 by joni

[joni 0]

Found this elsewhere from DrSarty!:

'Replace like with like.

 

The temp operating range is stamped into the body of the switch usually, or it's indicated by a coloured plastic band.

 

Here's a link to the range of switches, and is in a resource you'd benefit greatly from learning how to use. It's brilliant!

 

You should state what car/year it's for too when you have a problem.

 

Rad fan switches

 

You want item 5. To get to the main menu to look up other items just end the web address at "pug/".

 

These come from ECP, GSF and naturally main stealers. '

[joni 0]

have you tried cleaning up the sensor terminals first, they are known to get a bit furry, worth a try before splashing out on a new one

 

Sorry didn't see this till now. I'll check but i think they looked ok to be honest. Cheers, J

[joni 0]

Terminals are clean.

Just did a test - took the sensor out, manouvered the loom so it was poking out the top of the engine bay, reconnected the sensor, surrounded it by a wet towel and subjected it to a blow torch! First speed switch seems to be working ok (92.5 degrees according to the writing on the switch) but second stage speed at 97.5 degrees is not kicking in. Based on these figures it looks like my part number is 1264 24. I'll get a new switch.

I also have an underlying overheating problem which i suspect is due to the timing being too far advanced and causing it to overheat at low speeds. I like to advance the timing as much as possible to free her up at the top end of the rev range but looks like this is a bad idea if i'm going to be stuck in traffic (rare).

[smithy 1]

Terminals are clean.

Just did a test - took the sensor out, manouvered the loom so it was poking out the top of the engine bay, reconnected the sensor, surrounded it by a wet towel and subjected it to a blow torch! First speed switch seems to be working ok (92.5 degrees according to the writing on the switch) but second stage speed at 97.5 degrees is not kicking in. Based on these figures it looks like my part number is 1264 24. I'll get a new switch.

I also have an underlying overheating problem which i suspect is due to the timing being too far advanced and causing it to overheat at low speeds. I like to advance the timing as much as possible to free her up at the top end of the rev range but looks like this is a bad idea if i'm going to be stuck in traffic (rare).

 

 

Temp switch notoriously weak because they switch a live,with mine I got rid of all the wiring and resistor then made it so temp switch is now switching a earth to a relay coil. The relay then switches earth for fan motor, took live for fan and relay from shunt box so both are fused, hopefully no more overheat issues now

[joni 0]

Temp switch notoriously weak because they switch a live,with mine I got rid of all the wiring and resistor then made it so temp switch is now switching a earth to a relay coil. The relay then switches earth for fan motor, took live for fan and relay from shunt box so both are fused, hopefully no more overheat issues now

 

Sounds like a good idea. I could save some money and use my existing sensor switch and hook up the first stage switch to the relay. It would mean that the fan would come on at full power but that sounds good to me.

 

How much ampage do the fans take? I have two in place - one is wired to a switch. What i might do instead is have both fans, running at full power off one relay (30Amp - is this enough?) operated by the first stage of the temp sensor OR my switch in the car by the steering wheel so i have the best of both worlds and if the temp sensor finally gives up i can make sure the fan stays on!

 

I don't know how the fan is wired up exactly but i presume its along the lines of the first stage switch goes via the resistor the second stage switch goes straight to the fan? Hence how you get two speeds?

 

Update:

Reinventing the wheel again when Sarty's already done it! http://forum.205gtidrivers.com/index.php?s...ling+fan+ampage

Looks like the fans can draw up to 15amps so i'll need to use 1 relay per fan though.

Edited September 30, 2010 by joni