2017 Transit Custom AC Problem

[Nick.bryant]

Im really hoping that somebody maybe able to shed some light on my issue but basically I cannot get the ac to work.
its a 2017 2.0 eco blue, I initially started by having it regassed but didn't cure it so put it down to the compressor and replaced that with a brand new one, still didn't work so tried about 4 different relays again no luck.(only cheap ones off amazon if that makes any difference)
I can get it to engage the clutch by bridging 2 pins in the relay port.
I can't find anything that stands out in for scan, the fans at the front click on when I engage the ac in the cab.
The only thing that seems a little odd to me is that the evaporater core temp sensor is reading 50 degrees (this was a few weeks ago before ingot hot) but I would have thought that would jus make it run at 100% rather than not let it click on.
I can't remember what the pressure reading was in for scan but will check again tonight

I'm just at my wits end and have run out of knowledge and patience so any help would be greatly appreciated

[metalworker0]

i just made a search on google and:

Other than faulty clutch - which you don't have
Fuse which you're already checked
Relays which you've already swapped

The only causes left, that come up frequently are:

blocked pipework - at the expansion valve

or
Bad high pressure switch

all the best.mark

[Nick.bryant]

Wouldn't a faulty switch throw some sort of error in forscan etc, I did look into replacing the hp switch and ordered one but cancelled the order as I believed it was ok due to what I was getting in diagnostics,I located it behind the front bumper and tucked up the side of the condenser and couldn't for the life of me work out how to get to it.
Im gonna see if I can find some more info regarding the expansion valve.

[metalworker0]

believe the expansion valve contains a small orifice / hole, this is where the liquid turns into a gas and thus makes the cooling happen, the valve is the most likely place for a blockage.

testing from google AI

One method is to use a pressure gauge to measure the pressure on both sides of the expansion valve. If the pressure on the high-pressure side is significantly higher than the low-pressure side, it could indicate a faulty expansion valve.

meaning the test is to connect both gauges to the filler valves .. low side and high side

so you need the duel gauge ac tester apparatus, and need to know what are the normal pressures , and you need to do your jumper thing to get it running to test it

see Rainman Ray's you tube videos on AC , he's made a quite a few of them, and points out frequently what is normal and what is not on the gauges

https://www.youtube.com/channel/UC7qMMY ... kTDMz6vVXQ

all the best.mark

[Nick.bryant]

Thanks mate, I've just watched a couple of YouTube videos regarding blocked ac so will also check across the condenser tomorrow with a heat gun to see if there's much difference.

[Nick.bryant]

So I’ve hooked up some gauges and have a low pressure reading of 125psi and a high pressure of 100psi

[metalworker0]

Google AI

Normal operating AC system pressures in a car vary depending on the ambient temperature and the specific refrigerant used, but generally, the low-side pressure should be around 30-50 psi, and the high-side pressure should be around 150-250 psi. These pressures can fluctuate, so it's important to consult a pressure chart specific to your vehicle's refrigerant and ambient temperature for a more precise range.

so something not right

all the best.mark

[metalworker0]

And google AI again, with this question "ac low side higher than the high side"

If an AC's low-side pressure is higher than the high-side pressure, it usually indicates a problem with the AC system, often due to a faulty expansion valve or orifice tube, a blockage, or an overcharged system. This situation can lead to poor cooling and potential damage to the compressor if not addressed.

Does not say anything about not engaging the clutch though... and there will be some pressuire known as static pressure, when system is shut down .

i asked google this "is pressure present in ac system when not running"

and got this:

Yes, pressure is present in an AC system even when it is not running. When the AC compressor is off, the high and low sides of the system will equalize, resulting in a static pressure reading that reflects the refrigerant's equilibrium state. This static pressure is different from the operating pressures when the compressor is engaged and circulating refrigerant.

Perhaps blockage makes static pressure remain at running pressure and sensor detects this and stops it running.

I then asked what static pressure should be in psi: "what is the static pressure of ac system psi CAR"
and got this:

The static pressure of a car's AC system is the pressure measured when the system is not running and can be used to assess whether the system is holding pressure and if there might be a leak. For an R134a system, static pressure should be roughly equal to the ambient temperature in PSI. For example, at an ambient temperature of 70°F (21°C), the static pressure should be around 70 PSI.

then :
"ac which pressure sensor will stop an ac systems clutch from engaging"

and got this .

The low-pressure switch is the AC pressure sensor that will prevent the AC system's clutch from engaging if the refrigerant pressure is too low. This safety mechanism protects the compressor from damage due to insufficient lubrication and overheating.

Here's a more detailed explanation:
Low-pressure switch function:
The low-pressure switch is typically located on the low-pressure side of the AC system, often near the accumulator or receiver-drier. It monitors the refrigerant pressure and, if it drops below a certain threshold, it opens the electrical circuit, preventing the clutch from engaging.

High-pressure switch function:
The high-pressure switch also plays a role in safety. It monitors the high-pressure side of the system and will also prevent the clutch from engaging if the pressure is too high, protecting the system from potential damage from over-pressure.

Importance of pressure sensors:
These sensors are crucial for the overall health of the AC system. They prevent the compressor from running when the refrigerant charge is low, which could cause damage to the compressor. They also protect against over-pressure conditions, preventing leaks or component failures.

hope it helps

all the best,.mark