Test Aircon performance

[nickmann]

Hi all.

I've been running my aircon on max cold for a day or two. I thought that seeing as how it's not done any cooling for several months I would give it a bit of a workout. (I should point out that it is always on, just that I usually have the dials on white which means I get warm air most of the time over the winter and won't get cool air till the outside temp is about 13 or 14 degrees.)

Well, as it happens the air seems less cold than I remembered. The little sightglass in the engine bay is full, with just the occassional swirl of bubbles, all fans operating normally, just the output don't seem too cold. It use to be really unbearably cold after 10 mins or so. I will try and measure the output temp later tonight.

There are no leaks, as evidenced by the sightglass, but maybe the refrigerant should be replaced? Thoughts? Comments?

 

[prprandall51]

Polen filters: when they get blocked up they prevent the heating and cooling working at full efficiency.

When I got lazy and decided to save the cash by not replacing them on my old BMW, the entire ventilation system was eventually reduced to a lukewarm waft of air instead of a strong flow of hot / cold.

Changing the filters immediately restored the full air flow.
Philip

 

[prprandall51]

And another one: I have no idea about Mercs but BMWs have a big electric fan at the front that has three speeds (in addition to the viscous-coupled fan that runs off the front end of the engine). The fan is designed to come on at the low speed when the air con is switched on. The lower two speeds are achieved using a ballast resistor in the supply line to cut the voltage to the fan. The resistor for the lowest (air-con on) speed works very hard and frequently burns out after a few years (on BMWs...). Without the fan, the refrigerant will not be properly cooled as it passes through the condensor (the radiator-like thing in front of the radiator) so the air-con will not be able to work at full efficiency. Especially if you haven't changed your polen filters, either

 

[panason1c]

I was told by a specialist that you should briefly see air bubbles in the sight glass on start up of the air con and from then on the sight glass should remain clear.....however, if you continue to see air bubbles then that is indicating that the gas is 'low'.

As an aside......it is advisable to run your aircon for at least 10 mins every week or so to keep the seals in the compressor lubricated and thus lessen the chance of gas leakage, as may be the case for your vehicle.