krest
Member
Hi all...hopefully this is the place to be and learn all about any fixes needed especially any trade secrets kept under the bonnet so to speak 
500X AC not working
- Thread starter krest
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500X AC not working
Mike1alike
Established member
Hi and Welcome on the forum!
Tell us more about the non-working AC.
Tell us more about the non-working AC.
Hi all...hopefully this is the place to be and learn all about any fixes needed especially any trade secrets kept under the bonnet so to speak
Does the compressor run?
krest
Member
No..the clutch turns via hand but does not engage when the ac is turned on…need to identify which is the ac relay to test.
Mike1alike
Established member
Well... does the AC have refrigerant (freon)? If not, the presostat reads incorrect pressure for functioning and the compressor feed (12 V) is cut off. That's why clutch doesn't engage. It's almost never due to relay. I don't know which is tha AC relay, but you can do some voltage measurements on the compressor feed. And, first of all, make sure there is freon in the system.
krest
Member
I took it to an ac garage who put the gauges on and just said ’you have high pressure’…they didn’t say if it had freon or not..I suppose first thing is to establish the high pressure..I have pressed the valve to see if any gas is leased and did.
krest
Member
How would I know if there is freon as the garage didn’t say if there was or not.
Mike1alike
Established member
Well, there's no other way to know. But normally, there should be, if the pressure is high. If there wouldn't be freon, the pressure would be low. Would help to know the exact number of that high pressure.
The possible causes of ac not functioning would be: in the worst case scenario, the dehydration filter disintegrated and the silicagel capsules went through pipes and blocked them. This would be possible if the filter is old. So, what year is the car? Was the filter ever replaced? On this same line of clogged pipes, a simpler cause would be broken pressure switch (valve) that doesn't open any more. It remains closed, the pressure builds up and ECU turns the compressor off to avoid damage.
Other reason: the presostat is no working anymore and having no data for the system's pressure, the compressor feed line is cut off by the ECU. Here would be helpful to mesure the voltage on the compressor, when you turn the AC on. Also, would be great if you have a tester to connect to the car's computer and see if it reads the pressure. Also, you could see what errors are stored about the ac. If there's no reading, means the presostat is bad, a certain fact is that the pressure is high in the system. If you don't have a tester, you could just replace the presostat and see if AC works again afterwards.
Other reason: the compressor is not working. You can test it by feeding it 12 V. If it starts when you feed it, means that probably presostat is bad, but you should see that already while you mesure the voltage compressor gets, before you feed it separately. Or it means the pipes are clogged like in the first scenario, so don't keep the compressor running too long. Have someone inside the car to check if ac is working when compressor goes. If it works, the presostat is the fault. If it doesn't, the system is clogged by faulty pressure switch or worse.
If compressor doesn't start when you put 12 V to it, means it is bad and you need to go to AC service to first extract the freon from the system and then fix the problem.
The possible causes of ac not functioning would be: in the worst case scenario, the dehydration filter disintegrated and the silicagel capsules went through pipes and blocked them. This would be possible if the filter is old. So, what year is the car? Was the filter ever replaced? On this same line of clogged pipes, a simpler cause would be broken pressure switch (valve) that doesn't open any more. It remains closed, the pressure builds up and ECU turns the compressor off to avoid damage.
Other reason: the presostat is no working anymore and having no data for the system's pressure, the compressor feed line is cut off by the ECU. Here would be helpful to mesure the voltage on the compressor, when you turn the AC on. Also, would be great if you have a tester to connect to the car's computer and see if it reads the pressure. Also, you could see what errors are stored about the ac. If there's no reading, means the presostat is bad, a certain fact is that the pressure is high in the system. If you don't have a tester, you could just replace the presostat and see if AC works again afterwards.
Other reason: the compressor is not working. You can test it by feeding it 12 V. If it starts when you feed it, means that probably presostat is bad, but you should see that already while you mesure the voltage compressor gets, before you feed it separately. Or it means the pipes are clogged like in the first scenario, so don't keep the compressor running too long. Have someone inside the car to check if ac is working when compressor goes. If it works, the presostat is the fault. If it doesn't, the system is clogged by faulty pressure switch or worse.
If compressor doesn't start when you put 12 V to it, means it is bad and you need to go to AC service to first extract the freon from the system and then fix the problem.
krest
Member
1.6d reg 66...what is a presostat...I've watch YouTube vids on relay and pressure switch...need to check if power to the switch from relay then power at switch for the compressor...the car has been serviced via Fiat dealership.
"Freon" is a brand name. Used to be used on old CFC refrigerants, Not really used these days as it can lead to problems with putting the wrong gas in AC systems.
Gases used in Car aircon systems consist of
R12 (Freon) used up until the early 90s.
R134a used to the mid 2010s
R1234yf current
Yours being a 2016 Fiat 500x quite possibly has the latter, the R1234yf, as this started being phased in by most manufacturers around that time.
This is all largely irrelevant to solving your problem, but one thing is if you had "high pressure" then this alone can be enough to stop the aircon working if there is to much pressure the system will shut down.
You need a good qualified aircon person to take all the gas out of the system. Check for leaks then recharge it with the correct amount of gas (measured by weight)
If it is still not working, then you can start hunting around for other faults but until you have set the Aircon system as it should be you can't fault find if you don't know that the gas in the system is good.
Finally R1234yf needs different machines to the old R134a, as a result some garages won't be able to work on your car. This might be why you got someone tell you the system had high pressure and then didn't do anything about it, because he didn't have the means to do anything about it.
Please don't muck about with it without knowing what's going on. Releasing the gas knowingly into the air is illegal, so you shouldn't go pressing on the valves to let the gas out. Its a good way to cause burns as aircon gas can cause very nasty freeze burns in an instant.
The gas is also very dense and can cause asphyxiation by displacing the oxygen in the air, so again, don't mess about with the gas side of things
krest
Member
The garage was an ac specialist so they say and maybe as you said they need to fault find and so couldn't/wouldn't advise...the car was topped and serviced by the Fiat dealership two or three years prior so I suppose it was done correctly would think.
krest
Member
Surely checking for faulty relay & pressure switch would be the first go to as easiest and cheapest items to replace if they are broken!?
Mike1alike
Established member
Sorry. The presostat is the pressure switch. The one I ment to refer to above, is the one on the condenser.
The pressure and temperature sensor on the ac system stops the voltage feed to the compressor relay if the pressure is not between 2 and 26 atmospheres, low pressure means lack of refrigerant gas, high pressure means blocking of refrigerant gas at the expansion valve or faulty gas pressure sensor.
As you took your car to the ac service specialist and they said there's high pressure, measured with their machine, means that the pressure is above 26 atm. That is really high and that's why compressor does not engage, to avoid damaging the system.
You, personally, can't do much about it. You really should find an ac specialist willing to work on it an fix it. If the pressure is really that high, first thing to do is to get the gas out of the system.
krest
Member
Could you be able to tell me which is the ac relay so I can test if faulty..manual and YouTube do not pin point which one.
Mike1alike
Established member
I can't.
