Air Conditioner High Low Pressure

[borgward]

2013 Fiesta SE Hatch. AC stopped blowing normally cold air right before Texas to Ohio trip. Decided to do without until I get home in Texas. I suspected low on refrigerant. In Ohio my nephew installed gauges. Noted high side pressure before starting engine and abnormally high low pressure after starting. Probably blockage.

Compressor was replaced about 8 years ago. There is a bit of leakage from both Schrader valves.

 

[Chris142]

Waaaay too high! Is the condenser fan working?

 

[mk378]

375 high side is the problem. First thing to consider is do the condenser fans work.

 

[Chris142]

375 high side is the problem. First thing to consider is do the condenser fans work.

Hey that's what I said. He's about 2x what the pressures should be. Depending on ambient temp of course.

 

[Nukeman7]

I would suspect a partially/fully blocked expansion valve if the condenser fan is working correctly.

 

[borgward]

I do not see a "Condenser" fan. There is radiator fan on the back side of radiator. Not on right now as engine is cold and ambient air pressure is 64F. The condenser sits in front of the radiator. Don't see a separate "Condenser" fan. I always monitor the temperature gauge it it indicated normal engine temp while driving here.

 

[Nukeman7]

I do not see a "Condenser" fan. There is radiator fan on the back side of radiator. Not on right now as engine is cold and ambient air pressure is 64F. The condenser sits in front of the radiator. Don't see a separate "Condenser" fan. I always monitor the temperature gauge it it indicated normal engine temp while driving here.

Looks like that Fiesta only has a single fan to cool both the radiator and the condenser. It should normally operate when the A/C compressor is engaged.

 

[clinebarger]

I do not see a "Condenser" fan. There is radiator fan on the back side of radiator. Not on right now as engine is cold and ambient air pressure is 64F. The condenser sits in front of the radiator. Don't see a separate "Condenser" fan. I always monitor the temperature gauge it it indicated normal engine temp while driving here.

The PCM commands the fan(relay) on with A/C head pressure as well as coolant temp, Right around 250psi on most vehicles.

You need to hook up a capable scan tool & monitor A/C head pressure.

 

[Chris142]

The PCM commands the fan(relay) on with A/C head pressure as well as coolant temp, Right around 250psi on most vehicles.

You need to hook up a capable scan tool & monitor A/C head pressure.

He's well over the pressure needed to get the fan on

 

[clinebarger]

He's well over the pressure needed to get the fan on

I agree, What pressure is being reported to the PCM? What is the coolant temp? Does the fan work at all?

 

[spasm3]

I would unhook the fan, and jump 12v to it and see if it runs.

 

[borgward]

I agree, What pressure is being reported to the PCM? What is the coolant temp? Does the fan work at all?

I suspect the fan works as I was driving in mid 90F weather with no overheating. Will Hot wire the fan to see if it works as it is cool here.

I suspect PCM. Will see if it is throwing a code. when I am done with my visit.

 

[repairman54]

Most fans turn off above 35 mph as forward motion drives air through the rad / cond.
It should turn on idling with the A/C on at idle, at least at its slow fan speed mode.

 

[BrendanC]

resting static pressure looks high. may be over charged aswell. i would spray the condensor with a good degreaser and let that soak for a while, verify fan works, replace cabin air filter (if it has one) and evacuate the system. vacuum down for 30+ minutes and charge the correct WEIGHT of freon in.

i no longer just add freon to vehicles. if i have an ac problem, its full evac and charge by weight. never even look at the pressures. vehicle engineers went through the thorough thermodynamic calculations to specify charge weight.

 

[Chris142]

resting static pressure looks high. may be over charged aswell. i would spray the condensor with a good degreaser and let that soak for a while, verify fan works, replace cabin air filter (if it has one) and evacuate the system. vacuum down for 30+ minutes and charge the correct WEIGHT of freon in.

i no longer just add freon to vehicles. if i have an ac problem, its full evac and charge by weight. never even look at the pressures. vehicle engineers went through the thorough thermodynamic calculations to specify charge weight.

I do a lot of custom jobs. There's no weight given for those. I go by pressure and feel with my fingers.

 

[BrendanC]

I do a lot of custom jobs. There's no weight given for those. I go by pressure and feel with my fingers.

i also do LS swaps and with that custom AC systems. In those cases I charge off of R134a temperature charts. no guessing here.

 

[borgward]

resting static pressure looks high. may be over charged aswell. i would spray the condensor with a good degreaser and let that soak for a while, verify fan works, replace cabin air filter (if it has one) and evacuate the system. vacuum down for 30+ minutes and charge the correct WEIGHT of freon in.

i no longer just add freon to vehicles. if i have an ac problem, its full evac and charge by weight. never even look at the pressures. vehicle engineers went through the thorough thermodynamic calculations to specify charge weight.

Since compressor was replaced, system recharged about 8 years ago, I doubt it is overcharged or this problem would have exhibited itself years ago. Condenser and radiator cleaned last year while doing other things. Will verify fan even though coolant temperature is normal in hot weather. Time to change cabin filter. Last time I used non charcoal type. I could tell the difference. Will replace with charcoal type this time. Since the AC began performing poorly all of a sudden I suspect a control module. Will look into that and change the cabin filter when I get home.

 

[repairman54]

I just pulled a charcoal filter out of my '16 Equinox due to poor air flow. Not loaded up with junk either but it majorly restricted airflow too easily over only 5-6k miles. I initially thought there may be a rat nest in it. No more charcoal ones for me. I've seen standard ones go 50k miles too long in family vehicles full of junk flow better.
And I'm a every year filter changer as soon as spring pollen season dies down.

 

[Huskyguy68]

im no expert on vehicle AC, But google a d youtube AC Schrader valves.
Apparently its common for them to leak, and you can buy new schrader valves for cheap. Need a schrader valve tool to remove them, that too is cheap to buy.
So before you go spend a lot of money on AC repairs, google/youtube schrader valves.
I too have an ac leak and i suspect it might be both the high and low schrader valves.
i need to buy the valves and tools, and if it works, i can try an AC recharge kit next month on my 20 year old suv Nissan 2.5L.


Apparently, mechanics often realize the valves leak, but can be sneaky, charge you for hours of labor , pad the bill, and replace just the schrader valves, with the customer unsuspecting.
just saying.

 

[borgward]

I do not think they will be able to change the Schrader valves without loosing the charge, and then having to recharge the system.
Some inner tubes have a cap that doubles as a Schrader valve tool. I have one on each of my bikes so I do not have to carry the tool with me.