Ambient temperature display, complete retrofit.

[Jas11n]

Jas11n: correct "seed" with "speed"

It was late, that's my excuse

I have an A4 B5 temp display ready to be fitted. any tips on that? it is big, it will need some cutting, and the handbrake bulb on the cluster will have to be removed and replaced by a led.

I've never seen one, got a picture of it? (off to hunt in the FA)

[Skull]

Jas11n: correct "seed" with "speed"

I have an A4 B5 temp display ready to be fitted. any tips on that? it is big, it will need some cutting, and the handbrake bulb on the cluster will have to be removed and replaced by a led.

[Jas11n]

Can't add much more, apart from saying it has a connection to the speed signal wire too. It'd probably still give a reading without that, but the displayed temp wouldn't take into consideration the wind chill factor on the sensor out front.
The wiring pinouts on the yellow connector on the rear of the clocks (that the ATD plugs into) are numbered above. A multimeter would easily confirm the integrity and continuity of the wiring between there and their respective terminations at the yellow and blue 26 pin connectors on the rear of the clocks. That leaves a check to see the continuity of the signal wire from the sensor and the condition of it's earth and the earth at the yellow 5 pin connector on the rear of the clocks.

[johne]

Basically, yes. The ATD is a simple unit that stands on its own just needing connection to the temp. sensor down in front of the radiator, +12v, ground and the panel lights. If it's got those it will work. The temperature sensor is a temperature sensitive resistor (a ntc one to be technical) whose resistance to earth changes with temperature.

John

[alg]

Ok on reading this it makes me think my previous specialist was useless. If you replace the sensor & dash unit & wiring checks out to dash then you are only left with a faulty earth to explain no (nothing at all i.e. no failed bulb BTDT) display. Correct ?

[nbvolks]

Thanks for the info again, especially good for the guys in the US or outside of the UK.
I say that as it must be noted we here in the UK don't have to worry about the ACC headunit and it's associated wiring, as we never got digital air-con or climate control on ours cars, just plain old manual air-con.

Jas..

hehe... you should just play it up, by saying it's because Audi knew the Brits and the Irish (if it's all RHD cars) are simply too manly to be bothered with hairdresser luxuries like auto climate control.

[Jas11n]

Thanks for the info again, especially good for the guys in the US or outside of the UK.
I say that as it must be noted we here in the UK don't have to worry about the ACC headunit and it's associated wiring, as we never got digital air-con or climate control on ours cars, just plain old manual air-con.

Jas..

[nbvolks]

Good bit of info there
I've never seen this black plug behind the clocks yet, have just been going off what others have reported. Be a good idea for those that have this black plug already there to check where it's respective pinouts actually go to.
An auto cq20v was never available here in the uk (FWD yes, quattro no!) but I guess a generic dash loom might have been used from the factory, same goes for early S2's.
Guy who lives near me is wanting me to fit this in his 2.3 5 pot cabriolet, be interesting to see whats behind his clocks.

Jas..

There were no automatic CQs here in the states either, but it seems that Audi just used a generic dash harness for the 80 models. In my case the black connector was not screwed down to the back of the cluster, but was taped down and away from the cluster on the line coming off the dash harness and going to the blue cluster clip/connector. Does that make sense?

I also solved my problem with using it along with the 3b auto climate control. I sort of cheated. I simply cut the line at the acc headunit for the exterior temp sensor and ran a line from that to the temp display in the cluster. The acc has two "exterior" temp sensors. One is up front near the grill and functions only as an optional point of reference for displaying the outside temperature on the acc display. The other is labeled as an ambient temperature display and is located at the base of the windshield where the air intake and fan for the climate control system are. This is the ONLY sensor the acc ECU references for exterior temp, if I'm looking at my Bentley wiring diagram properly. But acc headunit will also display the output from this sensor should it be lower than the sensor behind the grill.

hmmm...rereading that, that may not make sense, so I'll break it down...

sensor #1 at the grill: Sends temp signal to the ACC headunit.

sensor #2 at the fan/fresh air intake point: Sends temp signal to the ACC ECU and the headunit. It's displayed on the headunit only if it is lower than the temperature seen by sensor #1. Or in my case, it's displayed because now there is no signal to the acc headunit from sensor #1.

[Jas11n]

Good bit of info there
I've never seen this black plug behind the clocks yet, have just been going off what others have reported. Be a good idea for those that have this black plug already there to check where it's respective pinouts actually go to.
An auto cq20v was never available here in the uk (FWD yes, quattro no!) but I guess a generic dash loom might have been used from the factory, same goes for early S2's.
Guy who lives near me is wanting me to fit this in his 2.3 5 pot cabriolet, be interesting to see whats behind his clocks.

Jas..

[nbvolks]

My experience is that a black connector is for the automatic gear selection display. You can still use it but you will need to reposition the pins on the connector to be in the proper order. At least that's what I had to do for my 1990 CQ over here in the states. I'm also waiting to get another temp sensor, because as I should have realized, you can't split the line with the auto-climate control system since that just splits the sensor signal between the two. (ie: if it's 40 degrees F outside the climate control will read 20, as will the temp display in the cluster)

[Error404]

I'll give that a go once its a bit warmer outside

Thanks Jas

[Jas11n]

just out of interest, like Pete, my CQ already has the black connector behind the clocks and is missing the +12v pin - i've had a good look when doing my cambelt but couldn't see any redundant connector in the engine bay for the sensor.... do the wires just terminate somewhere in the loom for this?

I've bought a sensor and have the display in the S2 clocks i fitted.... i might just start from scratch

Excellent write up BTW Jas - extremely helpful

On that spare dash loom Paul had, it was just terminated in the loom. Well buried too inside all the other wires and black loom tape. I'd just run a wire from the new sensor through engine bay, the bulkhead to behind the clocks and connect it up to pin 2 of your black 5 pin connector. Other wire off the sensor connect to a ground point or the body in the engine bay.
+12v can be taken off the black/blue wire in position 16 on the blue 26-pin connector.

Jas..

[Error404]

just out of interest, like Pete, my CQ already has the black connector behind the clocks and is missing the +12v pin - i've had a good look when doing my cambelt but couldn't see any redundant connector in the engine bay for the sensor.... do the wires just terminate somewhere in the loom for this?

I've bought a sensor and have the display in the S2 clocks i fitted.... i might just start from scratch

Excellent write up BTW Jas - extremely helpful

[Jas11n]

Paulgo, don't be daft, I would have lost patience whilst getting that wire through that grommet

Thanks Greg

In answer to a PM, whole job took 90 mins tops

Jas..

[Greg_S]

Excellent guide chaps, ive made it a sticky too since very handy for ambient temp display bulb replacement