Automobile A/C advice
 

Need some advice from anyone with experience with the A/C system on cars. I'm about to take my BMW in to be serviced because the air is not blowing very cold. Before you say it's low on 134, there is another symptom that I think is related. When the air is functioning correctly, there is water discharged from beneath the car from, I believe, the evaporator. Since my problem started, there is no water being discharged and the distinct "smell" of the conditioned air is no longer present. Basically, the air doesn't feel "refrigerated" like it should.

Is the evaporator a part that breaks down? If so, could this account for the fact the air does blow cool but not really cold as it used to. I would like to have some idea of the system before turning it over, blindly, to the shop.

Thanks for any help.

The evaporator is just a radiator, it does not break down but it can get clogged with dirt on the fins.

The reason it is not dripping water is it in not getting cold. If you are lucky it is just low on charge and has a very slow leak. The leak should be fixed if they can find it.

Agreed with Glenn. The water is condensation drain when your warm outside air is blown over the cold evaporator. The evaporator is not getting cold so there is no condensation. The evaporator is very rarely the problem.

First have them confirm operating pressures. Pressures = temperature. If that checks out, then a scan of the HVAC control system is next with BMW or Autologic tool for DTC's. Lastly change the cabin filter with OEM quality (like Mahn)

Thanks guys. That helps a lot.

Also... Check that the water drain isn't blocked. If it is it will eventually overflow and leak into the cabin.

The most common leak on all a/c systems are the schraeder valves. They are very slow leakers sometimes. Remember airing up your bike tires in the spring? Same thing. Look for oil under the valve cap and around the valve for verification. You should always change them anytime the system is discharged.

A small leak could also be the shaft seal on the compressor. I've seen some that only leak when the compressor shaft is at a certain point in its rotation/rest. Those leaks are attributed to non use, drying the shaft seal out. Those leaks do get larger over time.

Never put stop leak in your system, find the leak and repair it.

Good luck!