Tails

There is no High Temperature Warning Light. MY89 onwards cars fitted with the digital Cluster the High Temperature Warning Light is displayed in the the three digital read out panels in RED.
The LH paned displays "ENGINE TEMP", the centre panel displays the "temperature icon" and the RH panel displays "TOO HIGH".

The alarm display is activated when the temperature is over 120 decrees C.

In Electrical Drawing 5 cor Model 1990 "ENGINE COOLING, HEATER, AIR CONDITIONER" the location on the drawing is K40. I could not find the actual location on the engine, as it is not shown on Drawing Sheet 13, but it maybe from the Temperature Sensor I & II located on the thermostat bridge, I think.

The high temperature warning take its signal from the coolant temp sender shown on drawing 4 field P26 and enters the Digital Cluster PCB via plug 4 terminal 15.

Tails

I will try and do some more investigation, however Stan may know, off hand, as the coolant temperature sender location should be the same on all S4's, GT's and GTS's (that is from MY87 through to MY95.

69gaugeman

My 90 GT has a warning light as well as the message. Yes the signal is extracted from the variable temp sensor, so it should come on based on the needle. If they added resistors to the needle it could be problematic.

After working Audi's for MANY years I just found out their dash temp gauge is more of an advanced idiot light. The temp shows 90 for any temp between 80 and 105, then moves past ninety if the temp is over 110. Neat and frustrating if you don't know about it. Was driving me crazy when looking at a reservoir leak but the gauge only showed 90. The ECU showed a temp of 104. The coolant tank was separating at the higher temp and weeping coolant. Replaced a thermostat and brought the temp back down and voila no more leaks. Keeps the needle in normal range so you don't worry about normal swings of temp (when A/C on, etc.) while driving.

flyrade

I just saw this pic of a 90 GT dash with the numbers on the temp gauge. Do you think I can use these temp numbers to calibrate my temp gauge?

Randy V

Post a pic of your gauge when the engine is at normal operating temp, with the engine running.

Tails

Yes.
The conversions for 40, 80 and 100 degrees C are as follows;
40 X 2=80 -10% = 72 + 32 = 104 degrees F
80 X 2=160 - 10% = 144 + 32 = 176 degrees F
100 X 2 = 200 - 10% = 180 + 32 = 212 degrees F

flyrade

Since my car is at the shop right now I can't post a picture of the temp gauge. However, when running at normal temp the needle on the gauge is right on top of the first line - the one reading 170 above.
And thanks for the conversion.

Rich9928p

My '79 928 engine temp was reading hot, near the read bar, occasionally going into the red. An IR temp gun indicated that it wasn't the engine temp over heating, it was an inaccurate gauge reading.

My volt meter also read low and the odo reset often didn't have enough "umph" to reset to zero.

The solution for this was to wire in a direct relay controlled (using ignition on for control - 5A fuse protected) circuit from a 30 circuit location in the central electric panel to the 12V input to the instrument panel. A direct ground link was also wired in. I now have the correct voltage reading AND the temperature reading is down where it should be.

My shop has done this "update" for several other ealry 928 owners and everyone is pleased.

My '79 instrument cluster lamps are on when the ignition is turned on. If later 928s are different YMMV.

Rich
'93 GTS Cover Girl
'87 S4
'79 now with correct voltage reading
'79 Euro track beast

flyrade

Rich - are you saying the entire instrument panel was not getting the proper 12 volts? If that's the case, I'll have my mechanic check the voltage on my panel since he has the car for other work right now.
Thanks for that input.

bogdann

Hi
I would only be concerned if the gauge was moving around during normal driving conditions. If it gets to a consistent position after it has warmed up and remains static I would follow post #2 to see if the temps were correct. Mine will rise if I am stationery in traffic on warm to hot days but go back to its normal position when I start moving.

Seems to be a lot of work to remove the pod to get it looking correct. My fuel gauge never gets past 3/4 full.

In post #19 isn't that the external temperature?

Rich9928p

Yep .... most of the older cars have low voltage to the instrument cluster ... why? Who knows, just is. A dedicated circuit clears the problems (from 1978 - 1985 is what I've been told by my wrench is what he's done) ... I would imagine this would work for all up to the new "electronic" clusters with the trip computer.

It also could be the ground ... "both" sides were fixed.

Hilton

Oddly.. it seems only the GT's have numbers on the temp gauge. S4's don't, including 5-speed S4 (thanks to Dave Roberts of 928 Specialists for pointing out that little oddity, as one of the ways of telling a car is a GT and not a 5-speed '89 S4).

Which leads me to believe that Tails' picture above is actually of a GT's cluster which I lent him, and not from his own car at all

On my 87 S4, with the earlier style of temp gauge, the needle sits just about horizontal.

When running during normal driving, my 89 sits in the same place as this other USA GT dash (from another thread):

flyrade

Thanks for everyone's input. I have a better understanding of the temp gauge and its possible problems and solutions.

Since my mechanic has the car, my only option now is to wait till I get it back. My temp gauge is just like the one on post #11, except without the numbers. Why they did not include the numbers on the 89 S4 is beyond me - that would have made things so much simpler. Also, as in post #11, I expect my needle to point directly at the left hand square when the engine is off or cold, and then I can calibrate as in post #2.

Since the timing belt and other work is being performed, I should get the car back later this week. I'll let you know how it winds up. But thanks again for everyone's help.

flyrade

It's interesting to note that the temp gauge numbers are the same in posts 11 and 27 as per the conversions in post 21. That gives me a high degree of confidence that the gauge in my car is the same.

However, my gauge in normal running would sit on the 170 mark as in post #27, which I did not believe is right, and why this thread was started.

flyrade

One other point Hilton. As in my post #28, does your temp needle sit on the square when the ignition is off, or when the car is cold?