Audi 90 Quattro engine sensor identification

Ecosse · 02-04-18, 03:11 PM

IMG_3361.JPG
Hi - I need some help and advice please regarding the functions of the electrical sensors on the KV engine .
The photo shows the area of interest !
There are two temperature sensors on top and below the coolant elbow attached to the head.
One on the top has two wires - the one below a single brown wire. What is the function of each ? I have replaced both but my temperature gauge still doesn't work ( despite re soldering the dash instrument panel ).
And the red overheat symbol on the dash illuminates very quickly - but the fan works and the engine doesnt seem to overheat.
Then - in the picture there is a spare plastic plug 2 wire brown and red - I cant find any purpose for this ?
And then just visible below the warm up valve there are 2 single wire sensors screwed into the block - purpose of these ?
I have spent some time trying to bottom out the non working temp gauge - even a dash swap didnt give a result so now suspecting a wiring / sensor fault .
Thanks !

mikes2 · 02-04-18, 03:36 PM

The single wire sender is for the gauge.

If you ground this wire, does the gauge move off the scale ?

The 2 senders close to the warmup regulator will be the oil pressure switches. The spare plug is probably for the after run cooling fan - not all cars had it but the loom would be common.

Ecosse · 02-04-18, 04:37 PM

Hi - thanks !
Grounding the single brown wire has no effect on the gauge - using either dashboards .
I have dismantled one dashboard and resoldered many joints to no effect .
Any further pointers would be much appreciated !

Mellis46 · 02-04-18, 06:15 PM

Er, is this a B3 90q? Talking about where the top radiator hose attaches to the cylinder head? Because on my KV the sender with the 2 pin plug is for the gauge and warning, the little bottom sensor is the coolant temperature sensor, (and grounding it will make the revs drop under warm up)?

In your photo i notice you havent got the proper plug on the end of the wires going into the 2 pin sender, have you got the wires the right way round? (!)

Mellis46 · 02-04-18, 06:59 PM

That spare plug, on a B3 90 with the KV you should have an injector cooling fan and a load of plastic ducting that collects air from by the gearbox and blows it onto the injectors, the fact your photo could be taken from this angle suggests it is completely missing, probably because it stopped working or the ducts got broken somehow..

Ecosse · 02-04-18, 07:19 PM

Hi - that is really helpful thank you.
The car us a 1988 B3 10v with a TSR Performance 2.6 litre conversion.
The car has been off the road 5+ years and is taking a but of fettling to get to run well and is not currently roadworthy.
No sign of any cooling ducts to the injectors !
The plug for the top 2 wire temp sensor had disintegrated so I have created some temp plugs - they may be wrong way round ! There is power to one wire . I replaced the sensor .
Sounds as if I need to concentrate on wiring from the top plug to the temp gauge !

Mellis46 · 02-04-18, 07:22 PM

I would have said so, if you have the same set up as me. The KV ended up in quite a few variants including the B2 and there are differences between cars it seems. Good luck with it

Ecosse · 07-04-18, 06:16 PM

OK - so with power at the engine sensor it was back to the dashboard - and the blue and brown wire from the sensor was present on one of the dashboard plugs.
So out with the dash pod again - dismantled and re soldered the plug tags on the board . I had concentrated last effort on re soldering the rings where the gauge screws to the board.
This time better luck - the gauge immediatly sprung into life with the engine running . One more task sorted !

02-04-18, 03:36 PM	#2
mikes2 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Location: Polmont Posts: 2,617	The single wire sender is for the gauge. If you ground this wire, does the gauge move off the scale ? The 2 senders close to the warmup regulator will be the oil pressure switches. The spare plug is probably for the after run cooling fan - not all cars had it but the loom would be common. __________________ 1991 90 quattro 20v sport 1991 90 quattro

02-04-18, 06:15 PM	#4
Mellis46 Aero Advocate Classic Audi Club Member Join Date: Aug 2014 Location: Lancashire Posts: 1,448	Er, is this a B3 90q? Talking about where the top radiator hose attaches to the cylinder head? Because on my KV the sender with the 2 pin plug is for the gauge and warning, the little bottom sensor is the coolant temperature sensor, (and grounding it will make the revs drop under warm up)? In your photo i notice you havent got the proper plug on the end of the wires going into the 2 pin sender, have you got the wires the right way round? (!) __________________ -1987 90 2.2E / Sapphire Blue (Rest in Pieces) -1989 90 quattro with Sport Equipment / Satin Black -1997 A4 Avant quattro TDI 110 / Tropical Green (Sold) Last edited by Mellis46; 02-04-18 at 07:01 PM.

02-04-18, 06:59 PM	#5
Mellis46 Aero Advocate Classic Audi Club Member Join Date: Aug 2014 Location: Lancashire Posts: 1,448	That spare plug, on a B3 90 with the KV you should have an injector cooling fan and a load of plastic ducting that collects air from by the gearbox and blows it onto the injectors, the fact your photo could be taken from this angle suggests it is completely missing, probably because it stopped working or the ducts got broken somehow.. __________________ -1987 90 2.2E / Sapphire Blue (Rest in Pieces) -1989 90 quattro with Sport Equipment / Satin Black -1997 A4 Avant quattro TDI 110 / Tropical Green (Sold) Last edited by Mellis46; 02-04-18 at 07:01 PM.

02-04-18, 07:22 PM	#7
Mellis46 Aero Advocate Classic Audi Club Member Join Date: Aug 2014 Location: Lancashire Posts: 1,448	I would have said so, if you have the same set up as me. The KV ended up in quite a few variants including the B2 and there are differences between cars it seems. Good luck with it __________________ -1987 90 2.2E / Sapphire Blue (Rest in Pieces) -1989 90 quattro with Sport Equipment / Satin Black -1997 A4 Avant quattro TDI 110 / Tropical Green (Sold)

02-04-18, 04:37 PM	#3
Ecosse Newbie! Join Date: Sep 2017 Posts: 13	Hi - thanks ! Grounding the single brown wire has no effect on the gauge - using either dashboards . I have dismantled one dashboard and resoldered many joints to no effect . Any further pointers would be much appreciated !

02-04-18, 07:19 PM	#6
Ecosse Newbie! Join Date: Sep 2017 Posts: 13	Hi - that is really helpful thank you. The car us a 1988 B3 10v with a TSR Performance 2.6 litre conversion. The car has been off the road 5+ years and is taking a but of fettling to get to run well and is not currently roadworthy. No sign of any cooling ducts to the injectors ! The plug for the top 2 wire temp sensor had disintegrated so I have created some temp plugs - they may be wrong way round ! There is power to one wire . I replaced the sensor . Sounds as if I need to concentrate on wiring from the top plug to the temp gauge !

07-04-18, 06:16 PM	#8
Ecosse Newbie! Join Date: Sep 2017 Posts: 13	OK - so with power at the engine sensor it was back to the dashboard - and the blue and brown wire from the sensor was present on one of the dashboard plugs. So out with the dash pod again - dismantled and re soldered the plug tags on the board . I had concentrated last effort on re soldering the rings where the gauge screws to the board. This time better luck - the gauge immediatly sprung into life with the engine running . One more task sorted !