Technical Mk2 punto coolant temperature sensor

[TONY55S]

hi,where exactly is the coolant sensor on a mk 2 punto 8 valve.
there are 2 connectors on the right hand side of the engine attached to inlet manifold,one has 2 wires,the other has 4 wires attached,is it 1 of these???
tony

 

[benny279]

coolant/temp sensor? look on n/s of engine where the coil pack is look down and you'll see a green connector thats coolant/temp sensor.

 

[TONY55S]

Yeah i unscrewed it with 22mm spanner,its located near gearbox,everything i read said it was on inlet manifold,how do i test it now i have it removed??

 

[benny279]

why have you removed it? whats the issue you was having? overheating? no temperature reading? need more information

 

[TONY55S]

The radiator fan is not switching on and off.the fan runs when i put power to it,and fuses are ok,so must be sensor.
But the sensor i took out is located on gearbox,and its basically a mechanical switch,put a metre acoss the 2 pins and when i pushed pin at the back of switch it made circuit,dont think its the one for the fan.

 

[benny279]

disconnecting temp sensor with igntion on the fan should turn on within approx 5 seconds, are you getting a temp reading on speedo? have you checked the connector for the fan for condition of the plug for any corrison/rust etc?.

 

[TONY55S]

dont have a temp guage in car,the fan runs ok when i give it 12volts,will see if fan runs when i take sensor out again.

 

[Ziggy122]

The Temperature sensor has a failsafe mechanism built in

when the cars ECU goes - Knock hello temperature please

And there is an eare silence from it the car goes and switches into limp home mode

Limp home mode does the following
A - Put the EML light on
B - The temperature guage may go off / red light come on but register cold
C - Overfuel, overfueling gives a cooler combustion = Less heat produced
D - The Radiator fan switches on
E - The car may reduce availible power, to help prevent excessive heat build up

In the haynes manual - there are all the resistances as the car warms up - using that you should be able to tell whats what if the sensor has failed

Next the Coolant temperature sensor is no where near the gearbox.... its on the inlet manifold on the cylinder head
Have a lookie here
2nd picture on the middle ish - is a green sensor on the manifold
Yes it actually is clipped in there so its part of the manifold

ziggy

 

[TONY55S]

removed sensor,ignition on,but the fan didnt run,i have a feeling that the screw in sensor attached to gearbox is not the one i am looking for,how would sensor on gearbox monitor coolant temperatur?
wheres ziggy?????

 

[Ziggy122]

removed sensor,ignition on,but the fan didnt run,i have a feeling that the screw in sensor attached to gearbox is not the one i am looking for,how would sensor on gearbox monitor coolant temperatur?
wheres ziggy?????

Sensor on gearbox = Speedo sensor

See post #8 - link to a nice big picture set

Eye candy

Ziggy

 

[TONY55S]

ziggy,if i disconnect the plug on the temp sensor,should the fan run then? and if it does should i buy a new sensor???

 

[Ziggy122]

ziggy,if i disconnect the plug on the temp sensor,should the fan run then? and if it does should i buy a new sensor???

it comfirms that the car is seeing the Temperature sensor has ""failed"" by disconnecting it

If by reconnecting it and it doesn't turn the fan off, it would say to me a dicky cable somewhere

Ziggy

 

[TONY55S]

ok put it another way,how can i find out if the temp sensor is faulty??
they are around 50 euro so dont want to buy one unless its definately faulty,
thanks,tony

 

[Ziggy122]

ok put it another way,how can i find out if the temp sensor is faulty??
they are around 50 euro so dont want to buy one unless its definately faulty,
thanks,tony

This is the hard part
But basically you can measure the resistance the Temperature guage is producing
the car knows how hot or cold the temp sensor is

For example as stated in my haynes mk2
All in celcuis btw

0c = 5.37k ohms (k/o)
20c = 2.50k ohms
40c = 1.15k ohms
60C = .57k ohms
80c = .3k ohms
100c= .17k ohms

I'd stick a temperature probe in the radiator cap and run the engine checking the resistance as it warms up

problems
- Rad fan will be running as you have to disconnect the connector to read temps
- So disconnect the rad fan power cable

A temperature guage in the radiator = water has been cooled, so its hard to tell if the temperature vs readings will match

Ziggy

 

[TONY55S]

just looked again,my car doesnt have that sensor as shown in the diagram,
mine is 188a4000 model,will have to get some photos up to see whats going on.

 

[benny279]

dicky cable

a what?

 

[Ziggy122]

just looked again,my car doesnt have that sensor as shown in the diagram,
mine is 188a4000 model,will have to get some photos up to see whats going on.

188a4000 = 1.2 8v engine

that picture set is a 1.2 8v

I cant say this any clearer - YOU WILL HAVE A SENSOR THERE

unless there has been a hooligan under there before and somehow remvoed it and left a bodge job in there


What makes you believe CTS is at fault?

Ziggy

 

[adam79]

Re: Mk2b punto coolant fan

Hi, it has been said loads of times but my radiator fan is not working,
I was in slow moving traffic and the engine started to over heat.


Having a look at the car

The rad fan was seized and the 50amp maxi fuse had blown.
I have put a fan in from the scrappy (Powered up by a 12v power source and it works)
New fuse in.
The temp gauge is working ok, but when I take the wire off the sensor the fan will not kick in, I have put a wire in to short the sensor wire.

I have checked the wiring from the fan to the battery and that is fine.
I switched the 2 red relays about and still nothing (my blower fan still works)
I changed the Big black relay, one from a scrappy so not 100% sure it is a good one.


Would the temp gauge still work with a dodgy wire? any idea where the sensor wire goes? is it direct to the ecu or via the battery fuse box?


I will check the sensor wire next but any other ideas?



Thanks
Adam

 

[judderbar]

Re: Mk2b punto coolant fan

Hi, it has been said loads of times but my radiator fan is not working,
I was in slow moving traffic and the engine started to over heat.


Having a look at the car

The rad fan was seized and the 50amp maxi fuse had blown.
I have put a fan in from the scrappy (Powered up by a 12v power source and it works)
New fuse in.
The temp gauge is working ok, but when I take the wire off the sensor the fan will not kick in, I have put a wire in to short the sensor wire.

I have checked the wiring from the fan to the battery and that is fine.
I switched the 2 red relays about and still nothing (my blower fan still works)
I changed the Big black relay, one from a scrappy so not 100% sure it is a good one.


Would the temp gauge still work with a dodgy wire? any idea where the sensor wire goes? is it direct to the ecu or via the battery fuse box?


I will check the sensor wire next but any other ideas?



Thanks
Adam

If you remove the fan relay and bridge the larger connections the fan should run without involving the sensor, ECU or their wiring. If nothing happens you need to troubleshoot the wiring to the fan from the base of the relay and ensure you have a good earth at the Fan.

 

[adam79]

Ok will try, thank you.


Adam