Black n Blue water temp sensors - 92' G60

[G60_91 0]

Ive had a broken dash water temp gauge now for bout 2 weeks and cant seem to find what the problem is.

 

The cooling system seems to be working fine. No problem with the fan, radiator, not losing coolant etc. I read on a thread somewhere to swap over the black n blue water temp sensors on the piping joint near the front of the block to see if its working. The temp gauge moves when i do this, but only upto about 70-72 degrees. Ive also read that you can unplug the blue sensor with the engine running to test if that one is working (as you hear the engine note change/revs drop and fluctuate). Thats working fine.

 

so, when i swap the black plug over to the blue sensor and get my dash gauge working slightly, i can still unplug the blue plug on the black sensor and get the drop in revs/change in engine note... does that mean there is something else wrong? is there any/much difference between the black n blue sensors? maybe one is more sensitive?

 

Ive also found today an extra clip thats not connected up to anything and cant find where its meant to go. Its off the same wiring as the black n blue temp. plugs, with 3 smaller spade type fittings lower down the length of the cable. Blue and green are connected up but there is a 3rd white and blue one which is just left unconnected.

 

I had some work done to it a month or so ago and dont know if maybe its been taken off and the guy just didnt know where to put it back on? The dash gauge WAS working after i had this work done tho so maybe it was loose and has come of its connection??!!??

 

Im a bit stumped and dont really know how to tell whats knackered and whats not anymore, any help wud be mucho appreciated.

 

sam

[Yandards 0]

Righto here we go.

 

Blue temperature sensor: This is the one that provides the ECU with the temperature of the engine which the ECU uses to calculate fuel injector opening time, provides cold start enrichment (more fuel) up to 60 degrees C, acceleration enrichment, after start enrichment, overrun fuel cut off at temps above 50 degrees C, position of the idle stab valve during startup. So as you can see the little blue bugger is critical in the smooth running of the engine. Without it or if it malfunctions the ECU assumes it has a warm engine and it also prevents firing point (timing) advance. So you will get a power loss as well.

 

Black temp sensor: Its sole purpose in life is to provide you with a temperature reading for the gauge in the dash, if the dash gauge isnt working then I suggest you change this. VAG part number 251 919 501 D assuming you don't have aircon.

 

The other part of the loom is a part of an odd one without more info. I take it the blue and green ones you are referring to are connected to switches on the top of the oil filter housing? Had a quick look at the wiring diagram for your model year, I am guessing the blue and white one is for the .3 bar oil pressure switch, the green one should go to the other oil pressure switch. Are you getting the oil light come on when you put the key in and put it into the run position without starting?

[G60_91 0]

No aircon on mine no.

 

dash Guage does work when i swap the plugs over, but doesnt work at all when black plug is on the black sensor. Wud that still happen if the dash gauge was faulty in anyway?

 

The blue sensor has been replaced fairly recently, will dig out the receipts and check when exacly.

 

Yeah oil perssure light comes on before turning it over, then goes away when started.

 

Gave the car a good going over today and noticed a few other bits to replace. The cable from the Knock sensor is slightly worn where some muppet had zip tied it to the water hose WAY too tight. Also, got a fairly small split in the short pipe running from the oil breather cap to the S/C hose. Need a new cat or a bypass puipe soon aswell.... Will be getting my wallet knocked outa shape this week as ive got to sort a new mortgage on weds.

 

cheers for the advice, will get a new dash guage ordered.

[Yandards 0]

I would swap the black sensor not the gauge, the blue one provides a different output due to the way the ECU needs the signal.

[Supercharged 2]

Yep - new black sensor needed (blue one is slightly different scale)

 

You can also test the black one being dead with a multimetre (set on Ohms)

 

 

That wire your on about on the same loom for the above connectors is fine (same on all UK cars I think)

 

Knock sensor - I have an original bosch one (known working) you can have for £20

[vdubCorrado 0]

so here's the deal with the Black and Blue sensors... when you swaqp them back and forth they're supposably capable of making the ECU or the gauges function properly... i have never had that be the case... it lets you know if one of them are functioning improperly but that's about it... and the reason i think this may be is because the black sensor has been updated i believe twice since i have been buying them regularly...

 

Black - gauges

Blue - water temp

 

replace them both they're cheap... i don;t think paid any more than what would be for you guys £15

[g60ff 0]

Knock sensor - I have an original bosch one (known working) you can have for £20

 

If G60_91 doesn't take you up on that i'll have it off you

[G60_91 0]

cheers for the advice guys. Supercharged, I will have that knock sensor off you if youve got it still? will PM you my details later.

 

Blue sensor is less than a year old, even found the old one wedged behind the dizzy against the engine!! Is it worth changing them both at the same time? Might just get both ordered and keep blue one safe and sound. Hopefully oil breather pipe shudnt be much?? or will i get stung for that?

 

Thats a few jobs hopefully sorted anyways. Now its time to think about the charger and exhaust. Charger is due to be rebuilt in just over 15k, but thats only going off the jabbasport certificate and the mot mileage so will look at getting it done in the next 5k or so.

 

cheers again ppl.

[dirtytorque 0]

Hi

 

 

Having same prob with my jreg 92 g60 i.e temp gauge needle does not move.

 

The black sensor has an infinite resistance i.e it is open circuit across its two terminals.

 

The blue sensor incidentally was 1.7 k ohms.

Is this the sort of region the black one should be in?

I guess the black one is duff?!?!!!

 

p.s I was reading the factory manual.

It shows the coolant temperature send unit connected to this gauge.

It has the wire colours as y/r.

 

The wires going to the black unit are not yellow and red.

Has anyone else come cross these types of discrepancies

 

I'm looking in the carrdo 1991-1992 engine code pg section,which should relate to my C.

[G60_91 0]

Hi dirtytorque,

 

mines working fine now and it was the balck temp sensor. New one was £22 from VW with new ring seal.

 

The black temp sensor on mine has two wires, one is y/g like an earth wire and the other is solid brown.

 

The blue temp sensor has the same y/g and has a br/white 2nd wire.

 

Is this the same as yours?

 

Also, in my excitement to fit the sensor and see if it would work, i didnt remove the header tank cap and got a nice spray of coolant and water all over my specs when i pulled out the old sensor as it was still under a bit of pressure. I would remove the cap if i did it again :oops:

[Yandards 0]

Hi

 

 

Having same prob with my jreg 92 g60 i.e temp gauge needle does not move.

 

The black sensor has an infinite resistance i.e it is open circuit across its two terminals.

 

The blue sensor incidentally was 1.7 k ohms.

Is this the sort of region the black one should be in?

I guess the black one is duff?!?!!!

 

p.s I was reading the factory manual.

It shows the coolant temperature send unit connected to this gauge.

It has the wire colours as y/r.

 

The wires going to the black unit are not yellow and red.

Has anyone else come cross these types of discrepancies

 

I'm looking in the carrdo 1991-1992 engine code pg section,which should relate to my C.

 

I take it this info comes from a bentley?

 

It will be a US spec wiring harness so may not be the same, the other consideration is that the wiring diagrams are by model year, this does not directly correlate to the year of registration. You may find as yours is a 92 that the wiring is different.

[Walesy 0]

Also, in my excitement to fit the sensor and see if it would work, i didnt remove the header tank cap and got a nice spray of coolant and water all over my specs when i pulled out the old sensor as it was still under a bit of pressure. I would remove the cap if i did it again

 

Also, try and change it when the cars been sat overnight so the engines cold, a face full of boiling hot water can be painfull!

[dirtytorque 0]

:cry: :cry: alas your advise about waiting for the engine to cool down came to late :oops:

 

 

Oh well you live and learn.

 

Yandards

 

yes info was from the Bentley manual,I will bear what u said in mind.

 

g60_91

 

yes mate colours on the wire are the same.

 

p.s

 

try gsf next time for the blue sensor,fair bit cheaper.

 

I changed both the blue and the black sensor but still the cool temp clock does not budge

 

:0(

[Supercharged 2]

p.s

 

try gsf next time for the blue sensor,fair bit cheaper.

 

I changed both the blue and the black sensor but still the cool temp clock does not budge

 

:0(

 

Did you test it before you fitted??? I am sure GSF sell 'seconds' when it comes to sensors - I once went in with a multimeter and out of 10 blue sensors, 3 were open circuit, 2 were off scale and the other 5 were all different readings...

[dirtytorque 0]

yeah,both the old and the new black sensor was open circuit.

 

Both the blue sensors are in the 1.7-2.4 k ohm range.

I think the blue ones are fine when I disconnect the blue one the engines running note drops etc...

 

So yeah the reading on the black one seems strange.

 

I did however swap the black and blue sensors around but the temp gauge still didn't budge.This test would only be valid if they have similar resistances at a given temperature,

I guess they do as everyone says to do this test!?!!?

[Supercharged 2]

Yep - get a new black one from VAG - they keep them instock...

[G60_91 0]

Yeah id heard about GSF parts in general so steered clear. VAG part was quite expensive, but its worth it for peace of mind They also had it in stock at the first small VW garage i tried . I feel much better on longer trips now i know the coolant temp.... the oil temps are a different matter which will require some money chucking at it soon. Seeing 130 degs on the motorway!