Technical Climate Control [frost sensor fault?]

[schlau2]

Hello all. I have stilo 2002 with climate control. But I can't use aircon because it doesn't start. When I press the AC button (button with "snowflake") nothing happens, even lamp on the button doesn't light up. And sometimes I get a error message on dashboard (where the mileage is) that says "coolant sensor fault". Maybe this is cause or anything else? Many thanks for any help.

p.s. Sorry for my English, it isn't my native language.

 

[john55]

got gas in the system?

 

[minimad99]

fuses?

 

[mally]

Is the outside temp < 5 degrees. It doesnt work if cooler than 5 degrees.

 

[schlau2]

I was trying to turn it on when temp was about +12 degree. I'll start with fuses, thanks.
Nevertheless, may that "coolant sensor fault" thing be cause of the problem or not? I wasn't able to find any information about this sensor

 

[schlau2]

Hello again I checked gas and it's ok. I went to fiat service and got checked by Examiner. It showed error "Frost Sensor". But a service guy said that he didn't know how to replace the sensor (Fiat Stilo is very rare car in our city and other services don't know either) I search in ePer and found 2 sensors for aircon (or climate) but they have not named (just "sensor") number 46545740 and 46723690 (see in attach number 5 and 6). Which is frost sensor? Maybe anyone knows how to reach the frost sensor (maybe can it be replaced by me?)
I really need your help. I'll appreciate any advice!

 

[Deckchair5]

You don't say which engine you have as almost each engine has a different system. All my information says that it's only the 1.2 engine that has a frost sensor as the 1.2 aircon is different again to the rest. If you have one then it's K86 shown here but this is ONLY the 1.2 engine.



Here's a 1.6 manual air con system rather than climate control and it doesn't have a frost sensor


If you have a frost sensor then the sensor will be right next to the evaporator, that's the small radiator looking item in the ventiliation control, as it will need to detect the evaporator temperature getting near to freezing

Evaporator

A frost sensor is more likely to look like item 2 here

(Although i don't know for certain as my car doesn't have one)

So what engine do you have? Do you have access to an electonics store?
There are some tests you can do if you're capable

 

[schlau2]

So what engine do you have?

2002 Stilo 1.6 Dynamic 5 door but Examiner says that I have the frost sensor and it has error..

Do you have access to an electonics store?
There are some tests you can do if you're capable

I have

If you have a frost sensor then the sensor will be right next to the evaporator, that's the small radiator looking item in the ventiliation control, as it will need to detect the evaporator temperature getting near to freezing

How I can reach the evaporator? Is this thing located in the dashboard or in the engine compartment?

Although i don't know for certain that's it as my car doesn't have one

This is odd.. If I get it straight you have Stilo 02 1.6 Dynamic. How could it be that you haven't the frost sensor and I have(or Examiner is lying)?

Thank you very much:worship:

 

[Deckchair5]

You have climate control and I have manual control air con so they are different systems unfortunately. You may have a frost sensor but it will be located right next to your evaporator
Have a look at the drawings above as I've put a picture of the evaporator location there now

You say your gas pressure is good, can you say what you've done? Was it carried out by an air con engineer? Has your air con ever worked? Did it suddenly stop?

 

[Deckchair5]

Here's some information for you and this for Stilos WITH climate control

It still seems that it's only the 1.2 that has a frost sensor but i can't be 100% certain. Maybe a forum Fiat tech can give more hands on knowledge there

I would guess it's more likely that your "coolant sensor fault" might be your linear pressure sensor and i've had a lot of dealings with that as I have one of those

Linear pressure switch

You can bypass some of the sensors for testing purposes which is why i ask if you have access to an electronics store

 

[schlau2]

You have climate control and I have manual control air con so they are different systems unfortunately. You may have a frost sensor but it will be located right next to your evaporator
Have a look at the drawings above as I've put a picture of the evaporator location there now

Sorry, I don't get where the evaporator is located.. Can it be reached in the dashboard (maybe behind the radio?) or in the engine compartment?

You say your gas pressure is good, can you say what you've done? Was it carried out by an air con engineer? Has your air con ever worked? Did it suddenly stop?

Only check the gas pressure and checked by Examiner. About gas it carried out by an air con engineer; Examiner by Fiat service engineer.
I bought the car not long ago, last owner said that it hasn't work about a year(he was in another fiat service and they said to replace frost sensor, but for some reason he didn't it and now that service doesn't exist)
Sorry for bad English..

 

[schlau2]

Here's some information for you and this for Stilos WITH climate control
View attachment 40590
It still seems that it's only the 1.2 that has a frost sensor but i can't be 100% certain. Maybe a forum Fiat tech can give more hands on knowledge there

Can you give me the link to that forum?

I would guess it's more likely that your "coolant sensor fault" might be your linear pressure sensor and i've had a lot of dealings with that as I have one of those
View attachment 40591
Linear pressure switch

You can bypass some of the sensors for testing purposes which is why i ask if you have access to an electronics store

I found out that it's coolant temp. sensor fault
How I can bypass the pressure sensor? Can I bypass frost sensor?

 

[Deckchair5]

I meant a Fiat tech on THIS forum as we have a few but they're probably in South of France right now as it's holiday time here

The evaporator is near to where your right foot is when driving so it'll be behind the panel close to your right foot. It's buried deep in the ventilation control box but you don't have to get all the way in there as you're just looking for a sensor very close to the evaporator. If you have a "coolant temp sensor" fault then that sure sounds like a frost sensor

If your air con hasn't worked for a long time then it'll be far quicker and cheaper to let an air con engineer check out the system.

You can bypass certain parts just for checking purposes and only for short periods.

 

[schlau2]

The evaporator is near to where your right foot is when driving so it'll be behind the panel close to your right foot. It's buried deep in the ventilation control box but you don't have to get all the way in there as you're just looking for a sensor very close to the evaporator. If you have a "coolant temp sensor" fault then that sure sounds like a frost sensor

Is this frost sensor located directly into the evaporator or the sensor located near the evaporator?

If your air con hasn't worked for a long time then it'll be far quicker and cheaper to let an air con engineer check out the system.

The problem that no one don't know how to fix it..

You can bypass certain parts just for checking purposes and only for short periods.

Can I use a resistor or something to temporarily replace the frost sensor?

 

[Deckchair5]

Is this frost sensor located directly into the evaporator or the sensor located near the evaporator?
Yes the frost sensor, if you have one, will be very near or touching the evaporator but as far as i know it's only the 1.2 that has one as that has a fixed capacity compressor

Here's a wiring diagram the air con with climate control. K86 is the frost sensor. As you can see, it's only the 1242cc engine type that has one

The problem that no one don't know how to fix it..
Ha! You just need a better air con engineer

Can I use a resistor or something to temporarily replace the frost sensor?
Yes you could

Do you have any problems with your outside air temperature display readings perhaps? As I believe your air con system uses the outside temperature sensor to detect if it's too cold to run the compressor

 

[schlau2]

Yes the frost sensor, if you have one, will be very near or touching the evaporator but as far as i know it's only the 1.2 that has one as that has a fixed capacity compressor
Here's a wiring diagram the air con with climate control. K86 is the frost sensor. As you can see, it's only the 1242cc engine type that has one

Until the Examiner says the Frost Sensor Error I think there is no possibility to start the aircon

The problem that no one don't know how to fix it..
Ha! You just need a better air con engineer

On past weekend I was in 3rd service.. The problem is that Stilo is very rare car

Can I use a resistor or something to temporarily replace the frost sensor?
Yes you could

Any chances to know the value of the resistor?

Do you have any problems with your outside air temperature display readings perhaps? As I believe your air con system uses the outside temperature sensor to detect if it's too cold to run the compressor

No, I haven't. Temperature sensor works and outside temp shown in display is correct (I compare it with weather report) The outside temperature sensor doesn't allow to start compressor if outside temp is cooler than 5 degrees, but I tried to start when it was 20

 

[schlau2]

Maybe you can say what kind of sensors (maybe name) on this pic. Number 5 and 6. Num.6 was replaced by last owner but it didn't solve the problem(it seems to me that num.6 definitely is NOT the frost sensor )
Maybe is num.5 is the frost sensor?
Do you hear about Solar sensor? What do it does?

 

[johnson550]

If your aircon hasnt worked for a long time the chances are it wont anyhow due to the time factor the gas will be flat it should be sort of fizzy yours will be like the top has been left off

 

[schlau2]

I refilled it up few days ago, pressure is ok
(if I correctly understand you)

 

[Deckchair5]

Yes I would think that you need to get this frost sensor error cleared whatever it is. The problem is that you shouldn't have a frost sensor on your system. The linear pressure sensor decides whether it's ok for the compressor to start or not. If the system pressure is too high or too low then it prevents compressor operation

You haven't said whether you have checked the fuses, there's a lot of them
F19 compressor activation
F16 air con control unit and compressor
F8 heater fan
F31 heater fan relay
F49 heater fan and air con control unit.
Particularly F49 as this should make the air con switch light work and turn the heater fan on to its No 1 slow setting regardless of whether the compressor starts or not
Let us know how you get on.


This is the solar sensor which detects how heat from the sun's rays will affect the climate control settings

The is an air quality sensor which detects air pollution entering the system and automatically turns on or off cabin air recycling. This item won't prevent your air con compressor starting though


The linear pressure sensor WILL prevent the compressor starting if the system pressure is too low or too high