OK, I've been researching this for a while, but don't know what to do with the current pricing. I am working on my 85 300cd. My AC works just a hair less then it did last year, however I have noticed it does something weird. I don't get any AC when it's raining. Any ideas on that? I don't know if there is a leak, but I haven't seen any dye stains anywhere (if that matters).

I want to do at least a semi-rebuild of the system, being price conscious. I don't really want to drop the $250 for a new compressor, but I plan on replacing the seals, dryer, and evaporator. I know most people here like to stick with the r12, and I would really prefer to do that. The biggest problem is that the best price I could find on r12 is $23/ea from a member here. I can go to any store and get r134a for like $4, and freeze-12 for just a little bit more.

The model number on the current compressor is 1131627, it doesn't say anything about r4. I don't know if it's the original, but the sticker says it contains r12, and the valves are still r12.

I don't know much of anything about AC other than what I have been reading lately, so any advice is appreciated.

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

It really depends on where you live, and how efficient you need your AC system to be. Here, I could never imagine using anything less than R-12, simply because the system works so much better with it. If I lived in Minnesota, R-134a might be fine.

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Bob
'82 300D Petrol B-G Metallic

If the compressor cuts off when raining, it sounds like the water may be causing the belt to slip. Check your belt tension.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

I live in N. Louisiana. The highs will be in the 100's plus humidity in July and August. I need efficiency, and I will need relief in a few months. Does anybody have side by side numbers of the different refrigerants, so I could see if it's worth the money to do?

One argument people use about freeze-12 is it is made of different chemicals, so it will break down and leak at a different rate. My argument is it's about 1/5 the price, is it going to be so inefficient that r12 will stay colder 5 times longer? I could completely drain and refill almost 5 times before making up the money from r12. Another question is will the compressor work for it to begin with?

__________________
My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Also, what did anybody that has messed with the AC use to pull vacuum on the system?

I was looking at prices, and ********az has a conversion kit. If I go to an r134 based refrigerant, is this one of the "death kits"?

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

More likely the system's low side switch is opening due to an insufficient charge or, the evap is too cold.

BTW, where can you get R134 for $4?

In Louisiana I can tell you that R134a isn't gonna cut it and you won't be happy. Trust me!
I have 3 W123's. One has R12, and is by far the best. Another has Freeze12 and it is acceptable. Not as good as R12, but better than R134a. And the 3rd one has R134a and it is fine until temps are above 90, then you can't get vent temps below about 50 degrees, which won't cool a car that started out at 135 degrees inside! I have some Envirosafe coming this week for that one, and I'm gonna remove the R134a and give that a chance. Just doing this because I don't have to break into the system and flush. If I'm not happy with that, then I will have to flush the entire system, replace o-rings, rec/dryer and will go with R12.
You should pay the extra price for the R12 as it will certainly be worth it. What is the cost difference, the price of dinner and a movie?
BTW, have had Freeze12 for 3 years now, and have had no "break down" of the different mixed gasses. RRGRASSI has had it for 5 years in his pickup and it has worked well. I think the person that spoke of the break down of the mixture was espousing "theory" of what could happen, but hasn't used the product personally.
In the end, it is your decision, but R134a isn't worth spending any $$$ on, so who cares if it is less?

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Jimmy, I'm guessing I need to take you for a ride in the " R134" SD.

Better bring a jacket.

http://store.lenzdist.com/product.php?xProd=717&xSec=42 - $3.79/12oz can

Whiskey, what all did you replace on your system to get a great r134 setup? I have read that some people got good results after replacing the the evaporator (I believe). The current one was made for r12, and it takes some modifications to make a good modern one fit.

Jimmy, thanks for the reply...that is exactly the kind of info I was looking for. You have a pretty close climate as I do as well. Did you rebuild all of your systems the same (same rebuild process)?

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

dog, I guess I hit everything just right. I saw a vent temp of 32f today with an ambient outside air of 92f.

My '85 SD has a twin tube condensor which came on the car from the factory.

I bought this SD last fall and the AC was marginal then. It had been converted to R134 so, I had plans to do the PF condensor and install a larger aux fan. This spring I found the system low so, yesterday I replaced the leaking shrader valves, pulled a good vacuum for at least an hr with the ar sitting in the sun and played around with various amounts of R134 while watching temps and pressures in the system.
I found the condensor to be marginal but I was able to get good results with a slightly undercharged system. About two cans worth.

Also, my fresh air flap is tied in the recirculate position due to a leaky vacuum pod.

Go get a IR thermometer. It was very helpful when charging the system.

Here's more good info for you:

Air conditioning and refrigeration is ALL about HEAT and the intensity of it! Air Condition is just a means of moving heat from one place to another. The amount of heat concentrated within a certain volume with determine it's temperature. If you remove heat from that same certain volume, it's temperature will fall (become cooler). The Automotive Air conditioning system is a mechanical means of acomplishing this, using compression to reduce a certain volume to a smaller size. That smaller volume still contains the same amount of heat as before, but now the heat is more concentrated within that smaller volume, and therefore it's temperature is increased. The heat is letterally "squeezed" out of the refrigerant gas. Then the hot high pressure refrigerant gas (could be approximately 180F to 200F degrees)is moved to an area where it's heat can be transfered to the outside air (condenser), it's temperature is therefore reduced, and still being under high pressure, it's characteristics cause it to condense to a warm high pressure liquid (could be approximately 130F to 150F degrees). The high pressure liquid refrigerant then moves to the refrigerant control, which is a calibrated designed restriction, (orifice tube or TX valve) that divides the high pressure side from the low pressure side, acting like a small garden hose nozzel, it allows a small stream of refrigerant to spray into the low side. The liquid refrigerant, now being under low pressure boils and ABSORBS HEAT from in the evaporator (could be approximately 30F to 35F degrees). The low pressure refrigerant gas and mist flow from the evaporator out the evaporator outlet pipe (could be approximately 45F to 50F degrees)to the accumulator, which provides a place for the excess refrigerant mist to turn to gas, and also has a bag of dryer chemical in it, to trap any moisture that may get into the system. Then the low pressure refrigerant gas is sucked from the accumulator, through the suction line, back to the suction port of the compressor (could be approximately 55F to 65F degrees), where the process begins again. At each portion of the Air Conditioning circuit, the temperature and pressure will indicate how the refrigerant within it at that point is behaving, and has a direct bearing on the air conditioning performance. As an example on the High Side, at the condenser, if the refrigerant is behaving properly, the refrigerant gas will enter at a high temperature, and the refrigerant liquid will exit at a lower temperature (because it has transferred heat to the outside air). The difference is the temperature drop across the condenser (could be approximately 30F to 40F degree drop at idle or 40F to 60F degree drop at 1500 RPM, and the high pressure gauge reading will corrospond to a value on the temp/press chart for the lowest temperature on the high side, meaning the high pressure reading on a R134a system should be 212 PSI if the refigerant is exiting the condenser at 135F degrees. If you don't have enough temperature drop across the condenser and high side pressure is too high, look at the possibility of an overcharge, air in the system, condenser, air flow and fans for a problem.
As an example on the Low Side, at the evaporatorer, if the refrigerant is behaving properly, the refrigerant liquid will enter and boil at a low temperature (could be approximately 35F degrees), and the refrigerant gas and mist will exit at the evaporator outlet pipe at a higher temperature (could be approximatly 45F to 50F degrees, because it has picked up heat from within the vehicle). Then the refrigerant gas and mist pick up more heat and are completely vaporized back unto a gas as they are sucked through the accumulator and through the suction line back to the compressor suction port. The temperature at the compressor suction port should be higher (approximately 55F to 65F degrees, because the refigerant gas/mist has picked up more heat and completely vaporized since leaving the evaporator). There should be approximately a 10F to 20F degree diffence between the evaporator outlet pipe and the line at the compressor suction port at idle, or 2F to 10F degree drop at 1500 RPM, and the low pressure gauge reading will corrospond to a value on the temp/press chart, meaning the high pressure reading on and R134a system should be 30 PSI if the refigerant is boiling in the evaporator at 35F degrees. If you don't have enough or any temperature drop from the evaporator outlet pipe to the line at the compressor suction port and the low pressure reading is high, look at the possibility of an overcharge. The correct charge will cause the line at the compressor suction port to be slightly warmer than the evaporator outlet, ensuring that liquid refrigerant will not be sucked back into the compressor. An overcharge will cause the system to not cool as well, pressures will be higher, and liquid refrigerant being sucked back into the compressor, shortening it's life. If you have very low pressure on the low side, the evaporator outlet pipe is much warmer than it should be, check for a low charge or restriction at the orifice tube or TX valve.

A good way to check all the line temps is with an infrared thermometer. It's the best thing since sliced bread, and I would'nt be caught dead without mine!

Here's some info and guidelines for using it:

Using the Infrared Thermometer:
If you have an infrared Thermometer, you can easily measure the temps of the lines and get the charge just right. It works best on Dark Surfaces, so before starting, neatly spray paint the surfaces you intend to measure with some Flat Black Spray Paint and let dry. Wet surfaces should be wiped dry before measuring. Hold the thermometer close to and pointed at the object to wish to measure temperature. Since there is so much hot metal in the engine compartment and hot air blowing in the engine compartment, these will affect the thermometer to make reading inaccurate. To minimize these effects, take your readings quickly to keep the thermometer from getting hot, allow time for it to cool between each use, blow cool air on it between each use. Use the thermometer only when the thermometer is cool and stable. You must also use a heat shield around the component you are measuring, to keep stray heat away from the thermometer. Using a piece of light colored cardboard is a good heat shield against engine heat, exhaust manifold heat, and radiator heat. Place the heat shield in place quickly and measure the temperature quickly, then remove the thermometer and heat shield quickly, so that the heat shield itself does not become hot. Allow the heat shield to cool between uses.

These are APPROXIMATE TEMPERATURE numbers and will vary according to application, make and model, but are still good guidelines:
FOR AUTO RADIATORS:
At IDLE - Inlet Tank temp should range from 155 to 185 degrees, depending on thermostat and cooling system condition.
Outlet Tank temp should range from 130 to 170 degrees.
IMPORTANT-the DIFFERENCE between the inlet tank temp and outlet tank temp is the most important factor to determine how well the radiator is doing it’s job, which is TEMPERATURE DIFFERENTIAL ACROSS THE CORE.
With the A/C OFF, the temp diff should range from 20 to 35 degrees.
With the A/C ON, the temp diff should range from 10 to 25 degrees.
If there are problems with a too low temp diff and overheating, check temps across the core for evenness, check air flow through radiator, check fan & fan clutch and check coolant flow through core.

FOR AUTO AIR CONDITIONING R134a SYSTEMS:
At IDLE - Condenser inlet temp 170 to 180, Condenser Outlet temp 135 to 150 (usually a 30 to 40 degree drop in temperature across the Condenser), Evaporator Outlet temp 45 to 55, Compressor Suction temp 60 to 70 (usually a 15 to 20 degree drop in temperature from the evaporator outlet to compressor suction port). With the engine IDLING, you want to adjust the charge so the line at the Compressor suction port is about 10 to 20 degrees WARMER than the Evaporator Outlet pipe, and with the engine running at 1500 to 1800 rpm, you want the line at the Compressor suction port to be about 2 to 10 degrees WARMER than the Evaporator Outlet pipe.

At 1500 RPM - Condenser inlet temp 190 to 200, Condenser Outlet temp 135 to 155 (usually a 40 to 60 degree drop in temperature across the Condenser), Evaporator Outlet temp 45 to 55, Compressor Suction temp 55 to 60 (usually a 7 to 12 degree drop in temperature from the evaporator outlet to compressor suction port).

At 90 degrees ambient, for R134a systems, look for about 200- 220 Pressures on the high side and about 25-30 Pressures on the low side at idle, and at 1,500 RPM look for about 220- 230 Pressures on the high side and about 20-27 Pressures on the low side.

Let me add one more thing to the discussion. When you choose a refrigerant, give some thought as to what you will do with it when service is required. That is, ensure that it can be recovered as is required by law.

The reason that I am not going to use hydrocarbons in my air conditioner is that it is nearly impossible to find someone with reclaiming equipment for hydrocarbons. It is easy to find someone for R12 or R134a and recovering the refrigerant costs very little.

That is, it costs very little UNLESS someone has added a sealer to the system. Don't do it! That stuff will cause expensive damage to the recovery equipment, and unless you can convince the serviceman that none of it has been used, he won't touch your car. Of course, you could use it and lie, but he WILL know when it destroys his equipment.

Concur. I converted my '82 300D to R-134a on the basis of predictions (in the early 1990's) that R-12 was going to become unavailable. The result was an a/c system which was ineffective above an ambient temp of about 85*F. The initial cool-down time was lengthy and the performance at idle (stop-and-go traffic ocnditions) was very poor.

I switched back to R-12 two years ago. Now it's like riding in a refrigerator. I would advise you to spend the extra money for the R-12. The money you save on R-134a won't keep you cool.

I agree too, when I had R-134a the system was only adequate up to about 90F. The r-12 performance is much better.

OK, I'm sold...I am going to suck it up and pay for the r12. There is really nothing more satisifying than when you get into a car blowing freezing air when it's 105 outside.

__________________
My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Vent temp of 38f yesterday in the Black '85 SD with R134. Ambient was close to 90f at the time this was taken. Fan was in 'auto' mode.

AC system is stock with the factory twin tube and fin condensor.

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