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Focus on the condenser!

By Richard Hawkins, MACS Contributor

In last week’s article, we focused on applying temperature testing to an evaporator in an orifice tube system.  In it we illustrated how and why a low liquid level in the evaporator can cause a large temperature differential between the inlet and outlet.  We also indicated how and why raising the liquid level will cause the temperature differential to decrease.  Now it is time to focus on the condenser.

There has been some information written over the years that indicates that the condenser temperature differential on both orifice tube and expansion valve systems should be in the range of about 20° to 50°.  That information pointed out that a temperature differential of greater than 50° would point toward either a refrigerant undercharge or a restricted condenser.  A temperature differential of less than 20° would point toward a refrigerant overcharge or lack of heat transfer.  Note: This is assuming that there are not any other problems in the system.

Based on some testing we have done in recent years, that information seems to have been written about systems that use fixed displacement compressors as our tests confirmed that altering the refrigerant charge on those systems can have a dramatic effect on the temperature differential.  See pictures #1 below and #2 below.  

However, vehicles with variable output compressors (especially electronically controlled variable displacement units) will often have condenser inlet and outlet temperature differentials which fall outside of those ranges.  We are talking about perfectly operating systems with the proper charges, not systems with problems.

A temperature test taking place on an orifice tube system with a fixed displacement compressor operating with the correct charge.  The 1.3° differential on the evaporator is acceptable and the 39.2° differential on the condenser falls in the 20° to 50° range which was referenced above.

The same system being tested a few minutes later with the charge having been reduced by 25%.  The evaporator differential increased to a huge 32.1° and the condenser differential increased to 62.8° which is well outside of the 50° which was referenced above.

 I have personally tested numerous low mileage vehicles with electronically controlled variable displacement compressors which had properly charged, perfectly operating systems and found the condenser differentials to be in ranges of about 55° to 75°. 

MACS also did test on some other vehicles with electronically controlled variable displacement compressors with systems which were properly charged and operating perfectly and found very low condenser temperature differentials (in the 10° to 15° range).  With this being the case, it is recommended that extreme caution be utilized when temperature testing these systems and arriving at a diagnostic conclusion and considering replacing a condenser.  See picture #3 below.

Condenser temperature differentials like these are often encountered on properly charged perfectly operating systems that use electronically controlled variable displacement compressors.

One of the most common questions asked in tech line calls is: How much refrigerant is in that system you are working on?  Check back in next week as we cover some interesting answers to that question.

One response to “Focus on the condenser!”

  1. Thomas Lech says:

    Condensers is a hot topic when a technician does not know the car had a poor quality aftermarket condenser installed.
    Case scenario that I see often on a weekly basis. To perform an accurate test the condenser must be OEM or at least almost exactly perfectly matched aftermarket the “number of fins per inch”
    “The number of refrigerant passage tubes”
    Mini aftermarket condensers leave off those foam strips that are glued on the top in the bottom or the side that block hot under hood heated air from rolling back around from the engine compartment back in front and reheating the condenser another large problem.
    And even the “number and the size of the internal dimension of fins inside the cooling passage tubes themselves”

    If you’re unfortunate to get one of the lower quality aftermarket condensers and try to run your test you’ll get some really bad numbers on hot days

    But on a mild or a cool day you may nearly see no difference at all.

    I’ve been called into shops or had customers cars come to me where compressors have been replaced expansion valves have been replaced receiver dryers have been replaced or fixed tubes have been replaced all by not knowing what was going on and technicians just stabbing at wild guess throwing darts at the wall and see what sticks replacement method.

    And the only problem poor quality aftermarket condenser replace it with OEM and the car would cool perfectly on hot days.

    On some hybrid vehicles that have poor quality aftermarket condensers installed. If the condenser was replaced in the winter time in a body shop after a collision the customer will notice no difference in the winter.
    What time in spring time or summer time the customer will complain of poor gas mileage because the engine is running all the time because the high side pressure is so high the electric compressor is drawing a lot of amps from the high voltage battery. Constantly draining the high-voltage battery cycling the battery much more often than it was designed to be drained and recharged and the engines are always turning back on to recharge the battery.

    So the customer thinks they need a tuneup and bring it to a mechanic shop and parts start getting replaced checking fuel system parts ignition system parts spark plugs a whole bunch of wild guessing starts going on and replacing parts for this poor gas mileage condition sometimes rough engine idle on small displacement gas powered engine cars.
    And the cause ? “ poor quality aftermarket condenser installed” costing the customer hundreds and sometimes thousands of dollars in unnecessary parts replacement.

    I think just this month alone , I’ve probably released a half dozen videos on bad aftermarket condensers come backs for body shops.

    Very many upset customers upset body shop owners were told by the insurance company to use aftermarket condensers, And not so happy insurance company adjusters and supervisors when I give them a second fill for having to diagnose find a leak the first time customer have to go into a rental car again part has to get ordered front bumper front of vehicle taken apart to re-move the bad aftermarket condenser and replace it with an OEM and then if it’s a R1234YF vehicle they get my astronomically large recharge bill at second tiime.

    I had one large range rover with the dual air conditioning evaporator’s that was nearly 3+ pounds R1234YF I believe with a total cost approaching $600 for a recharge. Two times in a row bad leakING condenser so I had a total of three recharges before they put the OEM condenser on.
    And every time they called me out to re-diagnose define why it wasn’t working was a minimum $173 just to look at the vehicle and drive out to it on top of the recharge cost.

    All that caused by poor quality aftermarket condensers.

    On all my work orders and I am a direct vendor for mechanical shops or body shops when I see a poor quality aftermarket condenser that is grossly under fined . Example. If the condenser comes with 21 cooling fins per inch and the aftermarket replacement condenser only has 16 cooling fins per inch you’re probably going to have a problem on a very hot summer day.
    On top of that if the factory condenser had 58 refrigerant cooling passages . The aftermarket condenser only had 46 refrigerant cooling passages on top of it having fewer fins per inch you’re going to see some really unusually high side pressure on very hot days.

    Not to mention on a hybrid vehicle or a electric vehicle the hybrid the gas engine will probably never shut off because of the high amp draw on the compressor

    And I see on 100% electric vehicles extremely short high voltage battery range reduction.

    This is a topic that needs to be looked into and discussed and brought to light.

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