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Old 07-04-2013, 08:43 AM
RhoXS RhoXS is offline
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Location: Florida
 
Join Date: May 2008
Posts: 394
Mein Auto: Z3 & X3
Assuming all the controls are set correctly, insufficient cooling is probably related to one of the following mechanical issues that you will need a qualified A/C mechanic to deal with.

- Low refrigerant. Contrary to what many people think, it is impossible to determine if the A/C is charged properly by measuring only pressures. Additionally, due to the small size of a typical automotive A/C system, the correct amount of charge can only be determined by "weighing it in" and the amount is usually only a pound or two and is required to be correct to within a single ounce. Even an ounce too much or too little can adversely effect performance. For this reason, any A/C mechanic that states he will just add a little gas should be instantly avoided. Only after carefully checking for leaks, to charge a system, shops use a computer controlled cart. The cart first recovers all refrigerant that is in the system, then establishes an almost perfect vacuum, and then very carefully recharges it by exactly weighing in the required amount. If the system then cools properly it was low on gas and now it is necessary to find and fix the leak (frequently a compressor shaft seal). One more thing, a system low on gas will cool to some extent but left running long enough the evaporator will freeze up and air flow will significantly decrease. In fact, a frozen evaporator is an excellent indication of an inadequate refrigerant charge.

-Bad expansion valve. Even with a proper charge, a bad expansion valve will either cause inadequate cooling or cause the evaporator to freeze up (if it is stuck open).

-Loose or damaged compressor belt or bad compressor clutch (not likely).

-Bad/weak compressor. A gauge set will help diagnose this.

In any case, IMO, you need to find a TRUSTED shop that regularly does A/C work and have them check it. A friend or neighbor that tells you they can fix it is something to avoid as they will have no way of properly charging the system. Unless they have a good gauge set AND an accurate temperature probe, to measure something called superheat (and probably subcooling too) there is just no way to determine if it is charged properly without recovering and then weighing in the proper charge from scratch.

Last edited by RhoXS; 07-04-2013 at 08:45 AM.
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