I thought it eats away at other components..like evaporators.

this is a good debate... I am good with things that bolt and unbolt, and moderate with things that involve electronics, but A/C is far from an exact science in my book.

Yes, moisture in the system indeed combines with the refrigerant and produces an acid. That acid eats away at everything.

That said, the acid does not form unless there is more moisture in the system than what the dessicant can absorb. That dessicant is there to trap the microscopic amount of moisture that would remain after proper evacuation.

Once the system is properly evacuated and charged there will be no moisture in the system unless there is a leak. As long as the system is charged there is greater pressure inside than outside, so nothing can get in.

If you want to get moisture in, just start replacing filter driers as a preventive maintenance item. Every time you crack open that system in any way you stand a good chance of getting moisture in the system. As long as the system is charged and working properly, don't do so much as connect your gauges to it. That is cracking the system with a chance of introducing moisture.

As far as changing the evaporator because you are working on the system, please pardon me, but that is about as absurd as anything I can think of. If that evaporator is not leaking then DON'T DISTURB IT! If it starts leaking and you have diagnosed enough to determine that it is indeed leaking then by all means replace it.

Beyond seeing that the evaporator and condensor are clear of lint, bugs and other obstructions and seeing that the drive belt is in good shape, I would HIGHLY recommend that you take no other preventive maintenance steps. When the system needs service, you will know when you start wiping the sweat from your brow while driving. Until then, don't disturb it.

Good luck,

Thanks, larry...I appreciate your insight

...and I do change it hot and often... dino 10/40 in the winter 20/50 in the summer

I do all my own AC service. It seams to me what you really need is a good electronic leak detector. This way you can spend a fair amount of time finding the leak yourself. Usually service facilities only give you a 10 minute once over and often leaks are missed. Once you find the leak youself then you can point it out to your mechanic and he will be very likely to fix it right.

John Roncallo

Just before I started including a/c repair in my repertoire, I got quotes on two cars from the trusted local mechanic. Both times the quote was considerably higher and more comprehensive than the job really needed. DIY a/c repair can pay off considerably returns. I can understand the mechanic wanted to replace almost everything to ensure a good fix and avoid a return customer, plus you don't really know what's wrong until you start tearing into some of these jobs.

On these two jobs, one was quoted $700 when it really just needed a new $25 relay, the other was quoted $1500 (more than the car's worth) when it only needed a new compressor and clean up the spring-lock couplings ($350 diy).

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95 E320 Cabriolet, 169K

If anyone is interested in learning it theirself I have a r12/22 recovery machine that will sell for $500 obo. It was given to an a/c type friend from work and he already has one. Last time I had one shipped it was ~$75 from Kansas to Georgia.

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Jim

This is a very good thread with some excellent comments. I particularly agree with Larry Bible regarding learning a/c systematically. Although it's not rocket science, it can be complicated and expensive if not done correctly. However, a system built or rebuilt correctly can last for many years. I have worked on quite a few of them over the years and have two complete rebuilds that are going on 20 years with original freon. Never a leak or problem. (Actually, I am always surprised when I start them up after winter and they work!) But, I have been careful, and was taught by a master at a/c work, my father, and we have all the tools necessary.

DS
87 300D
01 Dakota