Automotive Air Conditioning Information Forum (Archives)

540itouring on Fri January 10, 2014 5:19 PM

Year: 1999
Make: Ford
Model: Ka
Engine Size: 1300
Refrigerant Type: R134a
Ambient Temp: 10 deg
Country of Origin: United Kingdom

In early 2009 I retrofitted air con system from another car of same age and type and has always worked perfect apart from one problem . The car is a basic ford model Ka with a accumulator system AC . The car has just been recharged as I have done every year since I converted it in 2008. The aircon on days with outside air temp above 10 deg the ac will work perfect with no problems all the time but does not work with a outside air temp of 10 deg or below. When I start the car at 10 deg and switch the AC on the compressor cuts in for about 8 seconds and then I can hear the low pressure cycle switch trip out. The compressor will then not cut in again for another 10 mins or so when the engine bay warms up the ac system. After this point it will again work normal all the time . I have other cars and have read that the AC system only works at 4 deg or above so strange why this car only likes above 10 deg .

I need to put a manifold gauge on a colder day to check the pressures to confirm what I have but have replaced the low pressure switch with the same results. I wondered if it could be a part blockage in the Orifice Tube as this was not a new one when I fitted it ? The system blows very cold when the outside air is above 10 deg so just can not understand what it can be or is this normal for this model ? I was thinking a blockage causing the low side to go very low and hold low until the temp rises but I cant explain why it works perfect above this 10 deg ?

The reason I would like it to work on colder days is to help remove the condensation in the mornings from the screen. Any info for if this is a fault of normal please .

Thanks in advance for your help.

Dougflas on Sat January 11, 2014 3:32 PM

That is 50* F. You may be low on charge and the orfice tube is freezing up. When the engine bay heats up, the metering device (orfice tube) may have enough ambient heat to keep it from freezing. Try adding a few oz of refrigerant.
You should not have to add refrigerant every year. You have a leak in the system.

540itouring on Sun January 12, 2014 8:25 AM

I have looked at the outside air temp today and is about 5 or 6 deg c and the static pressure on the manifold is 2.4 bar on both high and low gauges. This must be why the low pressure switch trips out but I am sure the system has a full charge with no leaks. I only recover and vac it out each year as I have all the equipment and like to keep it in good condition . The system does not have any leaks and so I cant understand other than the static pressure will drop with outside air temp unless this is normal for a small AC car. The system only holds apron 650 to 700 g and I always charge to 700g. When the engine bay warms the ref up it works perfect with the return suction pipe at the compressor very cold so looks as system charge is ok ?

What do you think ? Can you get a adjustable low presser switch or a slightly lower presser switch . What presser would the Ford switch trip out at 50psi ?

Edited: Sun January 12, 2014 at 2:51 PM by 540itouring

mk378 on Mon January 13, 2014 8:30 PM

There's no need to recharge every year. If there are no leaks one charge can last for years, possibly the life of the car.

Static pressure depends only on temperature, specifically the temperature of a part that contains liquid and gas in equilibrium.

Turn-on pressure of 45 or 50 psi is typical for CCOT switches. They're designed for a certain swing of pressure to reduce the rate of cycling and clutch wear.

540itouring on Tue January 14, 2014 6:14 PM

Ok thanks for the info