Hello.

I'm from Sweden and i shall try to write in english as good as I can.

I'm sure you will understand my problem.

I have an Ocatavia 1.6 2002 with Climatronic AC.

When I had my car at shop for service they replaced the tempsensor because the tempgauge was hopping.

After that it worked OK.

But now after nearly a month I have another strange phenomenon.

The water temp will not become warmer than 70 degrees C.

I have noticed that the both fans, for the cooling water and for the condenser of the AC starts immediately after I have stated the engine. Even if the engine is cold. They run all the time.

It doesn’t matter if I turn on the heat or cold. They run anyway.

If I turn the AC completely off, the fans stops.

When the car is standing on idle the temp will rise to normal temp 90C and stands there stable.

But when I start to drive on a road the temp will fall to about 70C thanks to the wind through the radiator.

When I then start the AC the fans starts too and the temp will fall a little bit moore to 65C.

So only when the car is standing still in idle the and the AC is off the temp will rise to 90C.

So what is the problem?

It can’t be the tempswitch for the fan. The fan should be running all the time then and not be stopped when I turn the AC off.

And it can’t be the thermostat since the temp will rise to 90C and be stable there when the engine is idling.

Can someone please help me what the problem is?

With AC on the fans should always be on to keep the compressor cool so thats normal.

I suspect you are seeing the symptoms of a stuck open thermostat, so water is flowing all the time through the radiator even when its not supposed to be. When my old car thermostat failed it would never reach normal temperature unless stuck in traffic and would never rise above the point where it would usually be (90c in your case).

With AC on the fans should always be on to keep the compressor cool so thats normal.

I suspect you are seeing the symptoms of a stuck open thermostat, so water is flowing all the time through the radiator even when its not supposed to be. When my old car thermostat failed it would never reach normal temperature unless stuck in traffic and would never rise above the point where it would usually be (90c in your case).

It can be a stuck thermostat.

But I have another theory I want to test.

The manual states that “The cooling system of this engine is map-controlled by the engine control unitâ€.

I suppose the control unit gets values from temp sensors and then controls the opening of the thermostat and when the fan should be running.

Nearby the radiator outlet there is a temperature sensor named G83.

The resistance should be 1.5 – 2.0kΩ at 30C and 275 – 375Ω at 80C.

If the resistance has short circuit then the control unit must think the water is very hot so it will open the thermostat fully.

So I wish to measure up this temp sensor.

But I can’t seem to get the connector off the sensor.

It’s little space there so it’s hard to maneuver my hands.

It seems there is some sort of block for the connector

I have tried to just pull it right out but it’s stuck.

There are two slots on the connector and I have put a flat screwdriver in both slots and push at the same time I pull it out but it’s still stuck.

I’m afraid to break something.

What is the method to get the connector off the sensor?

Here is a picture of the connector were you can see the two slots.

I can't find anything in my manuals to suggest that the engine ECU has control of the cooling system.

I can't find anything in my manuals to suggest that the engine ECU has control of the cooling system.

I don't know what car you have or engine but in my service manual chapter 19:2 it states this.

See for yourself down below.

It looks like you have a stuck open thermostat.

see http://briskoda.net/forums/topic/191554-electrical-plugs/page__p__2285681__fromsearch__1#entry2285681 for how to remove the connector.

It looks like you have a stuck open thermostat.

see http://briskoda.net/forums/topic/191554-electrical-plugs/page__p__2285681__fromsearch__1#entry2285681 for how to remove the connector.

And, since the thermostat iself is a conventional "hot wax" type, there is no way that the EMS can control the thermostat. It could, in principle, control the cooling fan speed(s).

And, since the thermostat iself is a conventional "hot wax" type, there is no way that the EMS can control the thermostat. It could, in principle, control the cooling fan speed(s).

Actually, there are engines that control the engine thermostat. The wax capsule has a heater element embedded in it and that heater is controlled by the ECU.

IIRC, engines AVU and BFQ have this arrangement.

Actually, there are engines that control the engine thermostat. The wax capsule has a heater element embedded in it and that heater is controlled by the ECU.

IIRC, engines AVU and BFQ have this arrangement.

You learn something new every day. Surely that can only spoof the stat into thinking the engine is running hotter than it actually is though?

You learn something new every day. Surely that can only spoof the stat into thinking the engine is running hotter than it actually is though?

Not really...

On the AHF the stat starts to open at 85°C and is fully open at 105°C

On the AVU the stat starts to open at 105°C and requires 100% duty cycle on the heater to fully open

Not really...

On the AHF the stat starts to open at 85°C and is fully open at 105°C

On the AVU the stat starts to open at 105°C and requires 100% duty cycle on the heater to fully open

Ok, so how do you achieve an engine temp of 100C and a stat temp of "only", say 95C by heating the stat?

Ok, so how do you achieve an engine temp of 100C and a stat temp of "only", say 95C by heating the stat?

You are adjusting the duty cycle.

At 100% duty cycle, the stat is fully open at 105°C - 8mm more than at 0% duty cycle. In other words you are controlling the flow. When you increase the flow of engine coolant through the radiator, you cool the engine more.

Another way to look at it is...

At 100% duty cycle the stat starts to open at 85°C and is fully open at 105°C (same as the AHF)

The opening of the stat is dependent on the coolant temp+heating effect of the element. By using the ECU, you have a closed loop system. You can arrange for the engine to be hotter at low loads and cooler at high loads.

Actually, there are engines that control the engine thermostat. The wax capsule has a heater element embedded in it and that heater is controlled by the ECU.

IIRC, engines AVU and BFQ have this arrangement.

Exactly!

This is not a stat of conventional "hot wax" type.

This electronically controlled cooling system gives a more even and precise temp of the cooling water no matter what the load of the engine is or the temp outside.

Here below you can see how it looks like on my car.

The stat is at pos.9 and has it's own housing with the heat resistor that control the wax at pos.7.

And the ECU controls the heat resistor.

With AC on the fans should always be on to keep the compressor cool so thats normal.

I suspect you are seeing the symptoms of a stuck open thermostat, so water is flowing all the time through the radiator even when its not supposed to be. When my old car thermostat failed it would never reach normal temperature unless stuck in traffic and would never rise above the point where it would usually be (90c in your case).

I don't agree on this.

I have my hood open many times when the engine is running and I have very seldom seen the big fan running.

Why should it run if the temp on the water is low and the AC is set to heat?

Now it runs immidiately you have started the engine, even an cold engine. I am 100% sure it has never done that before.

There must be some fault in the system.

And if the stat is stuck at open, why does that affect the fan to run all the time? I thought there could be a sensor error or similar.

But now I have managed to take the connector of the sensor G83 on the radiator outlet, thanx rwbaldwin for the link how to do that.

The resistance should then be infinit and according to the diagram that corresponds to a very cold engine.

My plan was to fool the system by this and to see if the fan stops running and the stat to close but.....no.

The problem is still there. So I don't think there is any fault on this sensor.

So maybe it's a stuck stat then.

But I still can't understand why the fans runs all the time. Right after the start of an cold engine..

It doesn't seems to be that hard to loosen the stat. It's only 2 screws.

Do you think it's totally broken or can the stuckness be cured with some mild force or someting.

I think this advanced stat is quite expensive..

Edited 6 June, 201115 yr by rail

Actually, it is a hot wax type, but with a heating element embedded in the wax capsule.

Unfortunately, they stick open - just like the ones without the element. Sometimes you see that the spring in the stat is broken.

You can test the element with a multimeter but you MUST NOT apply voltage to the element when the stat is not immersed in water or it will be damaged.

You should also test the coolant temperature sensor as the this part of the control loop.

Actually, it is a hot wax type, but with a heating element embedded in the wax capsule.

Unfortunately, they stick open - just like the ones without the element. Sometimes you see that the spring in the stat is broken.

You can test the element with a multimeter but you MUST NOT apply voltage to the element when the stat is not immersed in water or it will be damaged.

You should also test the coolant temperature sensor as the this part of the control loop.

Which temp sensor do you mean?

The G83 at the radiator or G62 at the coolant distributor housing, pos.5 at the drawing in the earlier post.

Which temp sensor do you mean?

The G83 at the radiator or G62 at the coolant distributor housing, pos.5 at the drawing in the earlier post.

G62.

Do you have access to VCDS?

G62.

Do you have access to VCDS?

No, sorry.

I guess I have to take the car to the shop so they can read codes.

I don't think I can do anything more.

So I went to the workshop for Skoda cars with my cooling system problem.

According to the bill it was “defect thermostat housing†that was the problem.

They replaced it with a new one, part #06A121111.

The whole repair cost 262€…

I looked up this part on internet and it seems it is the complete housing including the thermostat itself.

You can buy the thermostat seperately which has the part #06A121114.

So I wonder if the housing was defect but the thermostat was good, why don’t they just replace the housing and use the existing stat? Sounds like that should be cheaper..Or maybe the housing don’t come separately without the stat.

Anyone who knows?

Anyway, now the temp rises to 90C and stays there stable. So it works 100% OK.

But despite this I found the action of the fans still puzzling.

Let’s take it slow…

The big fan is for the cooling of the radiator and the water in the system.

The little fan is for cooling the AC condenser, right?

But if my Climatronic is on auto BOTH fans starts immediately when I start the engine. Even on a totally cold engine. Even if I set the control to heat 28C both fans are still running.

Shouldn’t the AC condenser fan stop when I turn on the heat?

Both fans stop when I turn the Clima to econ or off. Well, that’s logic I think.

But….I’m 100% sure that the big radiator fan have not been running in the past when I have the clima in AC mode. Only the little fan for the condenser.

What watertemp requires for the big fan to start? It must be over 90C? And my car have never reached that.

I’m pretty sure that the big fan shall normally NOT been running even when I have the clima on AC mode. It only runs when the watertemp reaches a certain high level.

As it is now this big fan runs ALL THE TIME when I have the clima at auto. This can’t be normal. And I know it didn’t do that in the past.

It’s easy to check.

Can one of you guys set your clima at, let’s say 22C and auto, and then open the hood and see if both fans run. Do it when the engine is cold.

Let me know what happens.

Edited 10 June, 201115 yr by rail