Coolant temp gauge not working

[shonkers 6]

Hi guys i’m trying to get the temp gauge working again and iv’e found this grey wire had chafed in two places, is that a temp sensor? it looks like a crank sensor to me as it goes into gearbox or flywheel but it can’t be ‘cos it connects to wires 47 and 47a and a white wire with no number on it through the brown multi plug, anyone know the part number please? the gauge above it does’nt work either i think it’s the oil temp

[Gohn 68]

yeah that grey line with the black cylinder is your TDC (top dead centre) sensor

 

you didn't say but assuming yours is a GTi, this is Anthony from an earlier topic :

 

"Obvious one to check is the ECU coolant temperature sensor - blue 2 pin sensor, either underneath the dizzy (earlier cars) or on the back of the thermostat housing (late cars).

 

They tend to fail reading cold in my experience leading to the ECU giving constant warm-up enrichment, giving dreadful fuel economy and (presumably) high CO numbers on an emissions test.

 

Easy enough to test with a multimeter - should be somewhere around 2500-3000 ohm ambient, dropping as the engine warms up to something around 250-300 ohm with the engine at normal operating temperature."

 

wasn't able to find the part no.

[Tom Fenton 1,542]

11 hours ago, shonkers said:

Hi guys i’m trying to get the temp gauge working again and iv’e found this grey wire had chafed in two places, is that a temp sensor? it looks like a crank sensor to me as it goes into gearbox or flywheel but it can’t be ‘cos it connects to wires 47 and 47a and a white wire with no number on it through the brown multi plug, anyone know the part number please? the gauge above it does’nt work either i think it’s the oil temp

That sensor is an unused engine speed sensor used by an old piece of Peugeot special tooling. You can remove it and bin it if you like with no detriment.

If the water temp gauge doesn't work I would check the brown multiplug in the engine bay first of all, it can be the source of many electrical problems.

 

10 minutes ago, Gohn said:

yeah that grey line with the black cylinder is your TDC (top dead centre) sensor

 

you didn't say but assuming yours is a GTi, this is Anthony from an earlier topic :

 

"Obvious one to check is the ECU coolant temperature sensor - blue 2 pin sensor, either underneath the dizzy (earlier cars) or on the back of the thermostat housing (late cars).

 

They tend to fail reading cold in my experience leading to the ECU giving constant warm-up enrichment, giving dreadful fuel economy and (presumably) high CO numbers on an emissions test.

 

Easy enough to test with a multimeter - should be somewhere around 2500-3000 ohm ambient, dropping as the engine warms up to something around 250-300 ohm with the engine at normal operating temperature."

 

wasn't able to find the part no.

No, the ECU coolant temperature sensor does not have any bearing on what the dash gauges display.

[shonkers 6]

Sorry forgot to say it’s an ‘88 gti 1.6 with a 1.9 engine, that tdc wire is connected to the brown multiplug under the afm that’s why i thought it must be something to do with the temp gauges, i don’t get it why is the tdc sensor connected to temp gauge? so i don’t need to replace it then and can i leave it disconnected? I did change the blue sensor under the dizzy but that made no difference except that i don’t think it’s running as rich and fuel economy seems better

[shonkers 6]

Just re-read your post tom saying i can bin the tdc sensor, so that would leave the other half of the brown multiplug dangling doing nothing something doesn’t add up here, have i got the plug mixed up with another one? ‘cos they are different shades of brown

[welshpug 1,657]

Looks like the sub loom from brown multiplug is missing,

[shonkers 6]

Oh i knew something did’nt make sense, where does the sub loom come from? Iv’e niggling feeling that it’s since i put the 1.9 engine in ‘cos those two gauges were working before

[shonkers 6]

Right i think iv’e sussed it, there’s two sensors one long one short as in pic with no wires attatched that’s gotta be it, so i think i can just snip off the multiplug and connect wire 47 and 47a direct but i don’t know what the white wire does, thoughts please gents

[pug_ham 244 3 Cars]

 

The white wire is possibly the oil temp sensor, down the back of the engine on the back of the sump.

 

g

[shonkers 6]

Yes graham it is oil temp ‘cos when i put it to earth the oil temp gauge went to max so i’ll connect that to sensor at back of sump, i feel like i’m getting somewhere now, when i earth 47a the green one the water temp goes to max an when i earth 47 the pink one the water temp light comes on, but which sensor to connect to the long one or the short one? or just swap them over if wrong, thinking about it if i get it the wrong way round the light will come on straightaway

[Anthony 1,003]

11 hours ago, shonkers said:

which sensor to connect to the long one or the short one? or just swap them over if wrong, thinking about it if i get it the wrong way round the light will come on straightaway

 

The shorter sender is for the temperature gauge, the taller is for the warning light.  If you get it around the wrong way, the gauge won't move but the warning light will slowly get brighter as the engine warms up.

[shonkers 6]

Ah i see that makes sense thank you everyone for your replies