Just noticed my 1987 300SDL with 134A conversion has a leak on the pressure switch attached to the rec/dryer. How much oil should I put back into the system when I replace that faulty switch? It there way you can measure the amt of oil to determine the amt when it leaked.?

Any other things I need to do while system is open before I suction and recharge? The A/C has been running extremely well until I noticed the temp going up on idle due to A/C Fan not coming on. There is when I did an inspection and found the switch leaking yellowish oil. Thanks for the help!!

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a2


1978 280 CE silver
1986 560 SL black
1987 300 SDL cream
1994 SL 500 brilliant green
1997 E 300d dessert silver
2005 FORD F250 Superduty Crew cab 4x4

____ADMU____

There is no way to tell how much oil has leaked out.

Therefore, I should just recharge with can pre loaded with lubricant??

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a2


1978 280 CE silver
1986 560 SL black
1987 300 SDL cream
1994 SL 500 brilliant green
1997 E 300d dessert silver
2005 FORD F250 Superduty Crew cab 4x4

____ADMU____

Never use can recharges. You must have a set of gauges to recharge it. With out the gauges you can very easily overcharge the system and hurt its performance or even blow out a line from too much pressure. Fix the leak, take it to an A/C shop and spend the $100 to do it right.

I have a set of gauges and oil(ACkits.com) from previous repair when I replaced a leaky evaporator from an r129(SL500). Thanks for the suggestion.

I'm assuming that it is a good time to replace the rec/dryer as well.

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a2


1978 280 CE silver
1986 560 SL black
1987 300 SDL cream
1994 SL 500 brilliant green
1997 E 300d dessert silver
2005 FORD F250 Superduty Crew cab 4x4

____ADMU____

I just bought a 1995 S420, the seller said it has a leak in the A/C. She was told it was a expensive repair because it needed to be "changed over". I got the car for $2500, its in excellent condition except for the A/C problem, with 140k miles.

So I guess the car originally used R-12, and the system can be converted to R-134a.

After reading here and elsewhere about this car's A/C troubles, I'm wondering if it probably is a leak in the evaporator, and will need the entire dash disassembled to replace the aluminium core with a copper evaporator core.

I'm zipping down to LA and San Diego this week in the '87 SDL, and have time to go to Mexico and get a few cans of R-12. How many cans does it take to recharge the system, assuming its empty?

Is there anything else I need to know about this situation? Oil, sealants, laws, etc.?

Or you can convert it to E 12 and save even more! E 12 is compatible with oils from R134 and R12, but E 12 takes much less energy to complete the cold cycle and therefore uses less fuel and engine power!

Since it's also environmentally friendly, you don't need a special permit to handle it!

Thanks Knightrider, I will look into E12. Do you have any links to more information about it?

How many cans do I need to fill the A/C system in the S420?

If you are just changing the switch, you can bleed out the old freon very slowly andthen just add back an oz of oil.. Swapping the drier is supposed to be done every time you open the system to air.. I have done something simple like swap out a switch without doing the drier. Only if the system was open for just a few minutes..

If you swap the drier, add more oil 3 or 4 oz.

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Bill

Backyard Shadetree Mechanic, 30 years running.

1987 300TD
1988 300E (sold, sniff)
1999 S320
1981 Volkswagen Rabbit Truck (Diesel)
2001 Ford Expedition
1988 Suzuki Samurai
On my list to buy: R129, for me, and a R107 for my wife.

One small thing you might want to know before proceeding with your plan is the A/C system on a 1995 S420 uses R134a - not R12.

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98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)

Since E 12 is lighter than R 12 or R 134A, you don't fill by the number of cans. You fill with a set of guages by the PSI you put into the sysyem!

E 12 is a replacement for R 12 and R 134 and it will work with the lubricating oil from each!

You will have to order it online but it is shipped out really fast.

http://www.es-refrigerants.com

After using E 12, the first thing I noticed is the AC compressor does not place a big drag on the engine and fuel economy goes up! You dont want to put anymore than 55 PSI in the low side of the system though!

Also, and this is important, charge the system by shaking the can first to properly mix any fluids and turn the can upside down and put in E 12 as a liquid!

Tim,

Thank you very much for that info. I was unable to find that important fact anywhere on the net..

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.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

Thanks obwielnls: I was thinking of the same amt. Just wanted to have someone reassure me of that. Happy Motoring!

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a2


1978 280 CE silver
1986 560 SL black
1987 300 SDL cream
1994 SL 500 brilliant green
1997 E 300d dessert silver
2005 FORD F250 Superduty Crew cab 4x4

____ADMU____