I have an 86 245DL and live south of I10 in Hades, err Houston. We have two seasons, August and the rest of the year.

Depends on how much work and money you are willing to spend, you can get an 88 to cool quite well.

The best working system is going to be a clean R12 System with a new expansion valve. The down side is the coolant is going to run over $100 and you will need a pro to install it. But if you flushed the entire system and replaced the dryer and expansion valve with new and get the system sealed tight, that is going to be the best cooling option.

The next option is using an alternative refrigerant like F12. Need a license to get your hands on it, but does work quite well. You will not get a pro to go near it once you have the gas installed. It will destroy the seals inside the recovery system. But if you were to install it in a clean unrestricted system, the results are pretty good. Ran that option for a while and liked how it worked. Sadly the compressor locked up and my F12/R12 source dried up leading to the next option.

Next best option is replacing the Compressor and Expansion Valve and converting to Pag 40 oil and R134. Flush the entire system and get old oil and gunk out of lines. Replace the Compressor and expansion valve R134 units, and change out the dryer. Replacing the Evaporator as you already stated would also help. You can get very respectable results with this set up.

The lowest cost option and also the least effective is the R12 to R134 conversion. You add mineral oil to the existing system and replace the fittings with R134 ones. With all that old oil and gunk still in a system, that seems to be a short term fix. Ran that system for a couple of years and it pretty much sucked. You prayed for the light to change so you could get up to speed and give the system time to catch up. This most likely works in places that have more than two seasons, you will sweat to death IMOH out in the desert and south of I-20 with this set up.

I now run the flushed R134 system without the upgraded Evap. Also have a Swamp Cooler (AKA Tropical Fan Clutch) and a pusher fan out of a 90's model under the hood. Makes coming to a stop much less of an issue by keeping the air moving across the coils. Anything below 95 degrees (even high humidity),no problem at all the system keeps the car nice and cool. However it does struggle in stop and go traffic in temps over 95. Once you get moving the system catches right up. I do plan to replace the Evaporator with the one out of a 90's model the next time the system is opened. I was going to call Tasca Volvo and order the factory one when the time comes.

My final observation is that you need to read up on how much oil and coolant you need and pay attention to that. Too much oil will make a system run like crap and a lot of the R12 to R134 conversions have that issue. The person doing it replaces the fittings and pours in a couple of oz of mineral oil and overfills the system. Then the blame is assigned to "Those R12 conversions just never work right". The next thing to watch is how much coolant you add, F12 and R134 both use the 80% rule meaning you use 20% less than the sticker calls for. For some reason a lot of pro's just add in the same amount and over fill the system. That leads to excess pressures, shortens the compressor life and it will not cool properly. In fact it will not really cool at all once the temps hit the low 90's.

No matter what refrigerant you go with, the key to success is to clean out the lines, drain the compressor, then to replace the expansion valve and dyer. Adding the correct amount of clean oil and the right amount of refrigerant to a tight, leak free, and unrestricted system is what is going to get you the best long term results.

Hope this helps,

Paul