I refilled my A/C a couple of times a year, then it got to where it would only work for a couple of weeks.

At that time I decided to do mine and am satisfied with the decision to do it. Including ALL efforts (web and book study/research, writing out a plan, finding, ordering and running for parts, the work itself, finding and re+nting an evacuation pump, etc), it took the equivalent of 4 days. Much of this time you will not be able to use the car, so plan for that. By working methodically and not rushing things I avoided breaking anything (such as plastic parts). Carefully label things as you pull them out. One of my sons worked with me through the entire job.

The posted instructions referred to are a very good starting point. You do need the TORX bits and the spring clip removers.

You need to remove the entire dash and climate control unit. There is no other way. You will be able to clean/inspect the plenum and heater core at the same time.

If other A/C parts prove to be bad you will be able to get access to them without removing the dash - unless it is a bad compressor which has sprayed metal fragments or other contamination throughout the system.

The issue of bending the lines on the evaporator was not so difficult - see some previous posts (including some with my name) on this issue. The evap is a durable aluminum part.

Not long ago a posted on a couple of things I ran into that you might watch for.

There is one more item I had not mentioned - there is a very large red connector (at least on the 850) which is the main connector for the dash functions - it swings open on a hinge. It was very hard to remove the retainer clip on this and I damaged the clip some. The connector did not want to stay together when reassembled, resulting in appearance of a number of check engine codes and erratic running. I secured this with a nylon wire tie and it is still ok (about 4000 miles later).

All told, the decision would depend on what your time is worth.

I replaced the evaporator in my 96 850 earlier this summer and overall my reaction was that it was not as bad a job as I expected. I'm glad I did it myself -- saved a bundle. It does take a long time because of all the steps but most were very straightforward -- and mostly "clean" too, just unscrewing parts in the interior. I would consider myself an average DIYer in terms of skill and experience although I am fairly slow. It took me 1+ days to finish, mostly because I forgot some things in re-assembly and had to back up.

I'd say you definitely want to follow some good directions to you use the right sequence of steps. I followed those found at: www.volvo-forums.com/t2756-evaperator-replacement-instructions. These are really detailed and accurate. I did find one or two slight deviations that were apparently due to changes by Volvo from year-to-year, but that shouldn't be a problem.

You need to be careful to mark all the connectors etc so you can get the right ends back together -- there are a zillion wires dangling when everything is apart.
And it really helps to have an extra body to help lift the dash in and out -- but it is not hard to do, just too long and awkward to handle by yourself.

As far as special tools, you do need spring lock disconnectors (I bought the cheap set of them at Sears) and the torx drivers. I had to make an extra trip to Sears because one of the torx drivers needs to be especially long -- I forget which. The web instructions have a list of the sizes you need.

Good luck if you do it.

No one wants to spend a lot of money to fix an AC system. ALL of our 850/70 series will have evaporator leaks, and it is a pain to repair. The real problem is the fact that the "new" evaporator isn't any more reliable than the old one.
Yes, the dash has to come out and that takes 2 mechanics all day, and they supposedly know what they are doing. It is not for the novice. Besides, once the system is hooked back together, you will need to have the system vacuum pumped out and r134a replaced.
If you belong to VCOA, and your dealer accepts their 10% discount, ask the dealer for a discount?
I am putting off having mine replaced, it is cheaper to add a can of r134a every 4 weeks or so. Besides, winter is almost here in Minnesota, I can wait until next May for my next can!

Klaus

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(1975 164, 1995 854T, 1998 V70R)