Technical Air Conditioning Problem – Fiat Grande Punto 1.2 2007

[hoxty]

Hello everyone,
I have a problem with the A/C in my Fiat Grande Punto 1.2 (2007). The refrigerant gas is full. When I press the A/C button, most of the time the compressor does not engage. Sometimes it works and when it does, the cooling is excellent.

The issue is that:

The A/C often refuses to start, even though the gas is present.

When it works, the cooling performance is very good.

Sometimes, when driving at low speed or stopping in traffic, the A/C suddenly cuts off.

After it stops, it usually won’t start again unless I completely switch off the car ignition or press the A/C button many times.

I already checked all fuses and relays ? they are OK.

I replaced the compressor control valve ? problem still exists.

I replaced the A/C pressure sensor ? problem still exists.

So, the A/C is working intermittently. It seems to be an electrical or sensor-related issue, not a gas or compressor mechanical problem.

Does anyone know what could be the cause? Could it be the evaporator temperature sensor, wiring issue, or fan control module?

Any advice would be appreciated.

Thanks in advance!

 

[GrandePunto PL]

Algeria? It is on the hot side "a bit"...
Maybe 30-40°C is too much for old Punto?
Check eLearn, read all parts (description, functional description, wiring).

Manual A/C (you didn't tell which one you have, manual/auto): https://aftersales.fiat.com/elearnsections/main.aspx?nodeID=199001428&languageID=2&markID=1&modelID=199000000&valID=199000000&prodID=199000000&modelName=Fiat - 199 - Grande Punto&langDesc=English&sectionName=Impianto Elettrico&validityName=1.2 8v

Compressor engagement: https://aftersales.fiat.com/elearnsections/main.aspx?nodeID=199001443&languageID=2&modelID=199000000&valID=199000000&prodID=199000000&markID=1&isExaminer=&dhb=AIR CONDITIONING - DESCRIPTION&modelName=Fiat - 199 - Grande Punto&langDesc=English&sectionName=Impianto Elettrico&validityName=1.2 8v
There are conditions and restrictions to it. Maybe that's why it's disengaging periodically.

Someone has to diagnose it, not swap parts.
Measure pressures (High, Low side) and pressure transducer ("sensor") voltage output.
Maybe you have too much refrigerant in the system?

 

[hoxty]

Thanks for your answer. Yes, I live in Algeria and the outside temperature is often 35–40°C in summer. I understand that high ambient temperature makes the system work harder.
understand that high ambient temperature makes the system work harder.
Here is what I already tested:

• With the scanner, the refrigerant pressure shows around 8 bar when the A/C is off, and about 14 bar when the compressor is engaged.
• When the A/C suddenly stops, the fans also stop at the same time. If I disconnect the compressor solenoid (valve), the fans work normally (low speed then high speed). When I reconnect it, I can hear the compressor engage for a second, then everything (compressor + fans) shuts down.
• I already replaced the control valve in the compressor and the pressure sensor (K120), but the problem is still the same.
• When it works, the cooling performance is very good.
• The system works perfectly when the weather is cooler, which makes me think it’s not a permanent blockage (expansion valve for example) but something related to pressure or electronics.

From what I see, it looks like the ECU (M10) is cutting the compressor due to an abnormal signal (pressure too high or too low), and since the fans are controlled by the fan control unit (M001), the shutdown affects both compressor and fans.


So, my question: has anyone here had similar symptoms related to the M001 fan control unit, or could this still be only an overcharge of refrigerant?

 

[jalopear]

Yo primero que haría es quitar gas refrigerante, parece ser una sobrecarga de gas.

 

[The Panda Nut]

It seems that there are 4 possible causes.
A poor switch
A faulty relay
A faulty thermostat
a bad compressor but that seems unlikely

I would identify and change the relay, or break the top off and clean the one you have.

MES would help check things out and does show the system pressure which on one of our yesterday was 10 to 11.5 bar with the engine running. There has been another post where someone had a faulty thermostat which fixed the problem. That was a 500 where the stat is housed in the dashboard.

 

[GrandePunto PL]

Manual or Automatic A/C?

PS
Which version of the MES, reads the A/C pressure (Manual type)? Older MES (and FES) does not have that parameter.

 

[Mike1alike]

Which version of the MES, reads the A/C pressure (Manual type)?

MES 4.7 can.
You can have it from here:

https://www.fiatfan.ro/forum/files/file/72-multiecuscan-v47r3-multilanguage/

 

[GrandePunto PL]

 

[Mike1alike]

Try this

MES 4.7

2 files sent via WeTransfer, the simplest way to send your files around the world

we.tl

I've uploaded it to wetransfer.

 

[Mike1alike]

View attachment 472676

I think you have to create an account on that forum first and log in. You can't access it because you're not logged in.

 

[GrandePunto PL]

Nope. For example MES 4.9 does NOT have an A/C pressure reading (manual A/C)!
Engines 1,4 8V, Euro4 (Grande), Euro5 (Evo). Manual A/C is managed by ECU.

Climate control module (connection via Yellow adapter) is for Auto version. But there is no "bar" value also.

Take a screenshot (where is that reading). Maybe it depend on the MES version (one do, others - older AND newer - don't read specific data).

---------------------------------------------------------- EDIT ------------------------------------------------------------------------------

By the way. Watch out using eLearn. There is an error probably. Pressure transducer ("K120 sensor") pinout mixed-up.

Plug. Pin numbering routine. Pay attention. Where is 1, 2, 3...spot the difference.

Example schematic/wiring diagram. This is the right one probably (diagram + picture above, connector pinout). To be confirmed...

So watch out while repairing the wiring harness, replacing damaged connector...

 

[Mike1alike]

Punto 1.2 8V Euro4, Manual A/C

 

[hoxty]

Yo primero que haría es quitar gas refrigerante, parece ser una sobrecarga de gas.

i removed some of gas the air condioning stoped

 

[hoxty]

It seems that there are 4 possible causes.
A poor switch
A faulty relay
A faulty thermostat
a bad compressor but that seems unlikely

I would identify and change the relay, or break the top off and clean the one you have.

MES would help check things out and does show the system pressure which on one of our yesterday was 10 to 11.5 bar with the engine running. There has been another post where someone had a faulty thermostat which fixed the problem. That was a 500 where the stat is housed in the dashboard.

thank you for your reply.
Can you please tell me where exactly the A/C thermostat (evaporator thermostat / sensor) is located in the Grande Punto? My car has manual A/C, not automatic climate control.
Also, I would like to mention that I have already replaced the A/C relay and the fan relays, but the problem still remains.

Thanks in advance.

 

[GrandePunto PL]

Punto 1.2 8V Euro4, Manual A/C

Punto_2, not Grande. So different ECU (it reports A/C pressure, others don't - MES version is not that critical, older v.3.1 has it).

 

[Mike1alike]

Punto_2, not Grande. So different ECU (it reports A/C pressure, others don't - MES version is not that critical, older v.3.1 has it).

Correct!

 

[The Panda Nut]

Sorry, I dont know wher the thermostat is in your but you may be able to identify this in EPER on here with a bit of effort.

 

[GrandePunto PL]

He didn't read the eLearn! https://aftersales.fiat.com/elearnsections/main.aspx?nodeID=199000630&languageID=2&markID=1&modelID=199000000&valID=199000000&prodID=199000000&modelName=Fiat - 199 - Grande Punto&langDesc=English&sectionName=Descrizioni&validityName=1.2 8v&isExaminer=
There is no mention of any "thermostat"! Expansion valve has some thermostat action built-in. That's it.

Compare it to Punto-2. There is (was) a thermostat/temperature sensor. But I digress.
https://aftersales.fiat.com/elearnsections/main.aspx?nodeID=3123047&languageID=2&markID=1&modelID=2000003&valID=2000308&prodID=2003009&modelName=Fiat - 188 - Punto Classic&langDesc=English&sectionName=Descrizioni&validityName=1.2 8v&isExaminer=
Google (LINK).

 

[GrandePunto PL]

Looks like Grande is reporting the AC pressure, but FES/MES author forgot to add this to the program! Let him know.
Competition is able to read this parameter. Example, AlfaOBD for Windows.

This is my faulty AC, doesn't cool (just a little bit) and makes hissing sound from the dashboard. Pressure is fluctuating like that.

Assuming this is a good pressure transducer. This graph must be confirmed with pressure check (both "H" and "L" side) is it really oscillating.

There's a leak somewhere and/or other issue (means bumper or dashboard out, probably). Maybe I will fix it next year (2026)...

 

[Mike1alike]

@GrandePunto PL, yours definitely lost refrigerant gas (the hissing sound in the dashboard is a sign, the expansion valve does not open completely due to low pressure) so it's better not to use it like that otherwise there is a risk to damage the compressor.
For fixing it dashboard does not need to be taken out and probably nor the bumper. If the bumper has that detachable low side part you can take that out and service the AC.
There is still some refrigerant gas in the system so that means there's no hole or cracks in it. So the leaks happened through the orings in the system and sevice valves. You need to put new orings and new service valves caps, refill and you'll be cool.
You have orings on the system at the end of every pipe that is connected to other part. Mainly there are 2 on the expansion valve (you find it under bonnet, I post picture), other orings on pipes connected to compressor and also the pipes to condenser plus pressure sensor.
The service valves are a strong leaking point and are usually ignored by specialists, probably because is good for their business. They leak small amounts of gas, but constantly and if you don't replace them you end up needing refill every year. I was told by refill guy that it's 'normal maintenance' to refill every year and he was encouraging me to do so. Bullshit. At that time I had new orings put in and the leaking point was the service valves. I got new valves and put them on myself before another refill and after that I have no leak in the system. Cold air works great and pressure is very good.