forum.audiv8.com Foren English Audi V8 Forum The direction :)

Hi and thanks for the great forum you got here. =)

And now to the subject.. The temperature sensor for coolant, does the resistance get lower or higher when motor heats up?
She is '93 4.2l quattro, if it does matter somehow.

I've got some broblem with her when accelerating slowly, she doesn't know should she go or not. Hesitating might be a word for the action.

as for your question, I unfortunately do not know that.
As for your "hesitant acceleration", the most likely culprit for that is the oxygen sensor aka lambda probe. I`d disconnect that one and then see if the problem goes away. Have you pulled the fault codes yet?

Not yet, hoping to get my Ross-Tech cable today. My thought about the hesitating action is something about the air flow sensor, but as well it can be the oxygen sensor altought the exhaust gas was in limits at vehicle inspection.
Also to mention the dashboards temperature which shows the coolant(my guess?) temperature at start keeps showing -45 degrees, is this the same sensor that tells the ECU to add more gasoline?

hi,
the resistance gets lower when the engine is heating up.

The sensor in the cylinderhead has to have about 360 OHM at 22°C
and 70 OHM at 130°C coolant temperature.

When you look from cooler, in front of right cylinderset is sensor that says approx 700ohm when there is about 25 degrees and about 80 degrees it says 550ohm. Did I measured the right sensor? I dont know but the autodata says, that the ohm value in about 25 degrees should bee somewhere between 1,5 to 2 kilos. Picture might be best way to locate these kind of sensors

send me your email-account and I send you a picture.

There are three coolant sensors:

One is located at the back of the rhd cylinder head near the firewall and this is for the ECU-box.

One is at the front of the lhd cylinder head and this is for the coolant temperature indicator in the dashboard. (I guess, it´s the one you have checked). If it indicates 7oo Ohm, it´s worn.

The third one is located in the coolant radiator and it is for the electric coolant fan.

I took my data from the original Audi maintenance instructions and I guess, they are correct.

Tim,

I wonder: The common understanding is that both sensors in the front are evaluated by the cockpit instrument and used as a decision base for the cooling fan speed level. Is this incorrect?

So is the sensor in the cooler a real "sensor" or just a thermic switch like the one in the Type 44s? So does the cockpit have any influence on the fan speeds at all?

Thanks

Bastian

How come the dashboard sometimes shows the coolant temperature and sometimes not? is there somekind of logic?
If you have more pictures of other sensors locations ie. knock and air inlet temp etc. would be nice to found them too.

Hi Sam,
you have got mail and now you have explained what, your problem is.
I guess there are three possible reasons for the temporary indicator malfunction:
1. Broken or short circuited wires
2. Bad welding points in the dashboard. This is a well known problem.
3. Bad sensor G2

@Bastian (why do we communicate in English?)
There are two sensors (G62 and G2) and one thermo switch (in the radiator):
G62 is for the motronic ECU only
G2 ist for the temperature indicator in the dashboard.
I guess (means: I DON´T know exactly), the switch in the radiator is an additional switch for the cooling fan. Maybe even for the highest revolution level.
The cooling fan is activated by the dashboard ECU, witch is getting it´s data from the coolant temperature indicator.