Air Conditioner High Low Pressure

[Nukeman7]

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.

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.

You can change out the Schrader valves without losing the refrigerant charge or evacuating the system with a special tool like this Lichamp Valve Core Replacement Tool.

If you can't change out the valve core (or the valve core threaded interface is damaged), replacing the plastic dust cap with these Dorman 902-025 brass plugs and Teflon tape will prevent the refrigerant from escaping.

 

[clinebarger]

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.

Your only concern is getting airflow across the Condenser!!!

 

[borgward]

I am home from the trip now. No airflow problems at condenser or cabin.
I suspect the ECM. I have OBD Link reader but does not show anything about AC controls.

I have had occasional throttle problem. Its not the pedal or the throttle body and its controller. I usually unplugged the harness connector and made sure the contacts were clean and moisture free. Sometimes the connector would come loose and all I had to do was make sure it was firmly pushed in all the way.

I suspect the real problem is the ECM itself. On this last trip The throttle was no problem at 80 MPH highway speed, only at low speeds. I was driving at speed with the light indicating the throttle was acting up. I would stop to fuel up and then start the car up w/no low speed throttle problem. I did not fool with the connector as I would be traveling at 80mph for hours. I could go for about 100 miles before the warning light came on again. Next time I fueled up and immediately took off and the indicator light would stay off and the low speed throttle worked well for another 100 miles. This happened over and over. I am retired and rarely drive over 50 miles at a time so the throttle does not act up very often.

That's why I think the ECM is causing the Low side Hi pressure. what diagnostic tool will read ECM to see if it is causing the problem? Would somebody like Autozone be able to get a module reading? Is there some other AC module not part of the ECM that regulates the high and low side pressures?

 

[MaximumMini]

I am home from the trip now. No airflow problems at condenser or cabin.
I suspect the ECM. I have OBD Link reader but does not show anything about AC controls.

I have had occasional throttle problem. Its not the pedal or the throttle body and its controller. I usually unplugged the harness connector and made sure the contacts were clean and moisture free. Sometimes the connector would come loose and all I had to do was make sure it was firmly pushed in all the way.

I suspect the real problem is the ECM itself. On this last trip The throttle was no problem at 80 MPH highway speed, only at low speeds. I was driving at speed with the light indicating the throttle was acting up. I would stop to fuel up and then start the car up w/no low speed throttle problem. I did not fool with the connector as I would be traveling at 80mph for hours. I could go for about 100 miles before the warning light came on again. Next time I fueled up and immediately took off and the indicator light would stay off and the low speed throttle worked well for another 100 miles. This happened over and over. I am retired and rarely drive over 50 miles at a time so the throttle does not act up very often.

That's why I think the ECM is causing the Low side Hi pressure. what diagnostic tool will read ECM to see if it is causing the problem? Would somebody like Autozone be able to get a module reading? Is there some other AC module not part of the ECM that regulates the high and low side pressures?

A normal OBDII tool won't. You need something more advanced like an Autel. I have an X-Tool D8. For my Chrysler vehicles I also have the same tool the dealerships use.

The ECM controls engine functions such as timing, fuel injection etc. AC is normally handled by the PCM and BCM. Of course, it can vary from manufacturer. Some vehicles have a dedicated HVAC control module. Having a FSM (Factory Service Manual (if available) is the first thing I obtain whenever I acquire a different vehicle. The pressure varies depending on fan operation, ambient temps, compressor cycling to name a few. Lots going on there.

If you're having other module related issues then it could be a clue. I'd check ALL the wiring for possible damage, breaks, chafing, abrasion and poor grounds. The modules are well protected usually in beds of silicone or epoxy resin.

Ask around among your friends and friends of friends. LOTS of guys have advanced scan tools these days.

 

[borgward]

The fan is not working. I checked the relay in the fuse box. It is OK. Ran 12v to the big slot the relay plugs into. Still no fan. Broke my finger so won't work on the car for another month. Will check the rest of the harness to the fan then. Engine runs at normal temperature w/out the fan even in slow traffic.

The compressor makes such a racket that I am afraid it is bad. I have not run AC since I noticed it was not cold enough.

Considering buying gauges, vacuum pump and etc as I think I can buy them for less than it would cost to have somebody good to replace compressor, and a small Oxy/acetylene set so I can do my home AC repairs. Used to do AC work back in the dark ages.

I noticed that 2013 is the cut off date for 134 A for the Fiesta. Noticed that OEM compressor is the same all the way to last year the Fiesta was made.

 

[mk378]

The compressor noise is likely due to abnormally high pressure and it may be fine once the fan is working.

As you noticed keeping the engine from overheating really doesn't need the fan unless the car sits still for a rather long time.