General Punto mk2b air-condition problem

[jimzak]

Hi again, i have a problem with 1.2 8v Punto mk2b with air-condition. When i push the ac button nothing happens. What i have checked so far... The gas/freon what ever is ok, i check it in garage, the compressor when i sort the relay it works and send cold air in the cabin, i check the relay itself and seems to be fine. The garage when plug the ecu scan saw a problem to the pressure switch, change the pressure switch but again nothing. I measure with multimeter the plug from pressure switch, seems ok. The internal fan control when i push it, the ac light comes on. The heater when i turn it to hot, it doesn't come so hot but something like natural/warm air.

Another thing, in all wiring diagrams i saw the pressure switch have five wires, mine have 3 wires and I can't find a diagram for punto with 3 wire pressure switch...

Every help will appreciate

Sorry for my English, is not my mature language

 

[judderbar]

So you now have no fault codes and the system was repressurised after the sensor was replaced?

On my 5 wire pressure sensor wiring diagram the clutch operates from a relay. If you pull out the relay and short the two large fuse box contacts the clutch should work.


on the two small relay connections one side is always at 12V. The other side is grounded by the ECU to operate the relay. you can trace that wiring back to the ECU.

If you have no fault codes on the pressure switch I am supposing that side of the circuit is fine. The switch should be grounding one of the signal wires. The ground wire will be black with a coloured stripe.

 

[jimzak]

Thank you for replying, no the multiecuscan continue to saw fault at pressure switch. I changed it with new but nothing happens, i check the plug from pressure switch and seems to be ok.

 

[judderbar]

Thank you for replying, no the multiecuscan continue to saw fault at pressure switch. I changed it with new but nothing happens, i check the plug from pressure switch and seems to be ok.

What code do you get? does it have a description from Multiecuscan?


If you open the bundle of wires going to the engine ECU you should be able to find the two signal wires from your sensor. If the other wire is black with a coloured stripe then you can check it is grounded.

 

[jimzak]

Thanks again for helping me, I don't own obd, the car i take it in a official fiat dealer garage and that guy told me see at his computer "pressure switch fault". I live in a little town in Greece and here where i live no one can solve my problem. I change 5 garages and still nothing. If you remember i have and another problem with my speedometer and i fix it myself with your help in another post.
Is any chance the problem to be in a heater matrix or at temperature sensor that was attached on it?
I checked the plug from pressure switch and seems to be ok, if was a wire from ecu to pressure switch i think i have get 0 volts at wires.

 

[judderbar]

Thanks again for helping me, I don't own obd, the car i take it in a official fiat dealer garage and that guy told me see at his computer "pressure switch fault". I live in a little town in Greece and here where i live no one can solve my problem. I change 5 garages and still nothing. If you remember i have and another problem with my speedometer and i fix it myself with your help in another post.
Is any chance the problem to be in a heater matrix or at temperature sensor that was attached on it?
I checked the plug from pressure switch and seems to be ok, if was a wire from ecu to pressure switch i think i have get 0 volts at wires.

If you have zero volts at all 3 wires that cannot be right because there would be no way to check the switch in the sensor.

I dont think you have a temperature sensor at the heater matrix? Have you just got ordinary AC? Later models have climate control.

As far as I know the ordinary AC just cycles on and off with the load on the compressor dependant on the opening of the hot/cold vent and the ECU not allowing it to operate if the temperature is under 5C.


Anyway whatever system you have zero volts at all 3 wires must be a fault and probably just another broken wire.

 

[jimzak]

Sorry for miss understood, i have 5v and when i press the ac button I read somewhere between 8-14v. If was a broken wire i should had have 0v right? I have ordinary ac, but from diagrams i see a small temperature sensor at evaporation thats activate and deactivate the compressor, i am wrong?

 

[judderbar]

Sorry for miss understood, i have 5v and when i press the ac button I read somewhere between 8-14v. If was a broken wire i should had have 0v right? I have ordinary ac, but from diagrams i see a small temperature sensor at evaporation thats activate and deactivate the compressor, i am wrong?

I do not know exactly how these AC systems operate.


How is that 8-14V changing? is it just random?

Have you found the compressor clutch relay and checked that?

 

[jimzak]

No it's not random, if i remember correctly when i press the ac button at first scale (1) from 5v I read 8v and up to four scale it reach at 14v.
I check the relay out from the car with a 12v battery and I hear the clicking sound, in the engine fusebox when I sort there where must be the 30 and 87 pins from the relay, the compressor clutches and i have cold air in the cabin.

 

[judderbar]

No it's not random, if i remember correctly when i press the ac button at first scale (1) from 5v I read 8v and up to four scale it reach at 14v.
I check the relay out from the car with a 12v battery and I hear the clicking sound, in the engine fusebox when I sort there where must be the 30 and 87 pins from the relay, the compressor clutches and i have cold air in the cabin.

Those voltages at the pressure sensor changing with the switch setting seems very odd. Why would there be any relationship?? I cannot see how it can cause those voltages to change but the pressure switch and the fan motor most likely share the same earth at E3 between the radiator and fusebox. There is a small box there connected to the gearbox earth.

Are you able to provide any voltages when the pressure sensor is connected? you will have to back probe the plug or put a pin into the wires.

Pity you do not know what the fault code is!

 

[jimzak]

Thanks for your help, i will check the voltages again and i will post.

 

[judderbar]

Thanks for your help, i will check the voltages again and i will post.

I was under my car and saw I had a 3 wire pressure sensor.

As you look at the connections there are two that are closest together and nearest the clip. I got 5 volts on those two. With the clip at the bottom, the right most connection and the top connection gave me 4.6V. There was nothing on the top one and the left one.

There was no change between fan speed 1 and 4.

Those voltages you got are odd. I know if you measure the voltage at the fan motor you get very similar voltages across the fan motor for those 4 settings. Potentially there is a problem at the AC switch

 

[jimzak]

Thank you for your response, the truth is I haven't checked yet, maybe i was measure wrong or the problem was at pressure switch plug, i must re check, you got 5v at idle, or with ac on? Thanks again for your help!

 

[fiatodyssey]

Hi! I'm having a similar problem but I think it's a simple fix. Does anyone know where the aircon pressure switch is on the 2b 1.4 16v sporting? I've had a look behind the o/s wheel cover but can't see it! I think the wire has come off ? any help would be most appreciated please.

Thanks

 

[judderbar]

Thank you for your response, the truth is I haven't checked yet, maybe i was measure wrong or the problem was at pressure switch plug, i must re check, you got 5v at idle, or with ac on? Thanks again for your help!

Those voltages are with the A/C light on. I tested all the wires to ground without the AC light on and got zero volts

 

[judderbar]

Hi! I'm having a similar problem but I think it's a simple fix. Does anyone know where the aircon pressure switch is on the 2b 1.4 16v sporting? I've had a look behind the o/s wheel cover but can't see it! I think the wire has come off ? any help would be most appreciated please.

Thanks

ePER which you can look at on this forum shows the same parts drawing for condensor and pressure stat for the 1.2 16V and the 1.4 16V.

On my 1.2 16V the stat is under the lower hose. You can see the wiring from inside the engine bay if you stand by the wheel and look over the air intake hose

 

[fiatodyssey]

ePER which you can look at on this forum shows the same parts drawing for condensor and pressure stat for the 1.2 16V and the 1.4 16V.

On my 1.2 16V the stat is under the lower hose. You can see the wiring from inside the engine bay if you stand by the wheel and look over the air intake hose

Hey judderbar,

Thanks for your reply and link. I've looked for the switch but couldn't find it, assuming its located near the drivers fog lights/ ac pipes. Nothing on eper that I could see.

Maybe I'm looking at this wrong. Do you recognise this wire at all? (Attached pic) This is in the same area and I'm convinced it's something to do with the aircon...

 

[jimzak]

Yea that's is the plug from pressure switch, when you open the hood and you stay in front of the car, at your left hand you will see a white water flask, that wire going at the bottom left of that flask, up from the fog light.

 

[fiatodyssey]

Thank you for the help, I will be sure to check it out tomorrow. It's been driving me crazy!

 

[crankshaft]

Another thing, in all wiring diagrams i saw the pressure switch have five wires, mine have 3 wires and I can't find a diagram for punto with 3 wire pressure switch...

Just some side note:
The five wire diagram is for the Punto mk2a. Punto mk2b only has 3 wires for the pressure switch.
On the mk2a one of the wires goes from the thermostat in the AC evaporator to the pressure switch, maybe that's what is different, but I really don't know. Would be nice to have some diagrams for mk2b.

Fiat Reference: 51768498