300SDL R12 charge weight
 

Does anyone know the exact R12 charge for a 1987 SDL?
Martin

check on the radiator support
 

I believe my old car had a sticker or plate on the radiator support with the info on it.

http://www.peachparts.com/shopforum/tech-help/125704-r134a-conversion-126-how-many-pounds-r134a-go-system.html?highlight=r12+300sdl+lbs

see first post.

"Chassis sticker says 2.2 - 2.9 lbs of R12"- doesn't sound precise. 0.7 pounds out of 2.9 is about 25%. Any thoughts?

My stupid car doesn't have a sticker. The FSM CD says 7.5 cans of "Refrigerant Bottle R12," which it later says is approximately half a liter. The column next to "126" where it says (filling) "kg" is blank. It tells you to check the car sticker. What gives??!?! :confused:Didn't these guys know how much they put in, or did it vary from unit to unit or operator (Horst or Erheardt)???:mad:

Certainly 7.5 12-oz cans (regular baby R12) would be WAY too much.

Since I don't have a scale, I just use a thermocouple in the dash vent and keep adding until it quits getting colder (leave all doors wiiiiide open). YMMV.

The real FSM says 1.3kg or 2.8 lbs R12 for W126.
This is from 1985 FSM, so I'm not sure if anything changed for 1987.

In any case, either use the site glass until the bubbles go away or do some research and use a set of gauges.

Is the system empty now or just low?

Jeff

The MB FSM on AC warns against using the site glass for this procedure.
SLOWLY adding freon while checking the temperature at the vents is pretty safe since it will run just fine many ounces less than maxed out...you do not want even one ounce over or it will cause your system to be overworked in short order.
So that ' RANGE' was not being imprecise... but being honest... and safe....Also, sometimes the total volume of a system is change by things like which condensor,etc was installed... so giving that Range of amounts of refrigerant was proper.
I would suggest when having to add with no way to measure weight.. that some means of forcing air into the front of the radiator/condenser is needed... like a squirrel cage fan... right up at the front of the car...
By slowly... I mean once the system has enough charge to stay operating... to keep the cutout switch from cutting out... then a couple of ounces added at a time then STABILIZE for 15 minutes at high idle WITH that forced air at the front...
Once your temps in the center vents with the fan on LOW... get to anywhere near 40 degrees I would stop and enjoy the cool air.

The spec is 2.8 lbs.

However, the system works perfectly fine with 2.5 lb........as evidenced by the recent fill by the mechanic.........

And 2.80000000000000000000000000000000000000000000000000000000000001 lbs
should be avoided at all costs...

I was renovating the A/C completely in 2008 including the evaporator (painful) and charged the system with 2.8 pounds R12, got readings of 200/25psi at 75F and 45-50F at center vent.... but to be honest the cooling was never great. Today I am measuring 60 degrees at center vent with a 80-85F ambient.
So it could be that the system was never charged fully which is amazing because it should work with less than 2.8 pounds (2.5 for instance as Brian pointed out). maybe the reason is that I was loosing freon when changing the cans.... or there is air in the system? Or why do I have high temperatures at the vents?
In addition I might have lost some freon over the last 2 years.
How can I prevent overfilling? Martin

Did you pull a vacuum when you put the new system together?

Jeff

Sure I did.

Did you replace the R/Dryer ?
Did you flush the system ?
Why do you think you might have moisture in the system ?
When checking the air temperature at the center vents... did you have the blower on LOW?
Did you have the car at High Idle.. AND have some type of forced air system...like a squirrel cage fan directly in front of the radiator ?
Did you clean both sides of your condensor and radiator ?

IF you are low on refrigerant...
you can prevent overfilling by adding about 2 ounces of refrigerant at a time...and letting the system stabilize for at least 15 minutes before adding more... taking readings all the time...and stopping as soon as you get reasonably cool temps... like 40 degrees to be safe...
but those conditions mentioned above are crucial... the forced air into the condensor area, clean and straight fins, etc..
If that does not work other trouble shooting will need to be followed...

The '86 would always present 60°F. vent temperatures and never would cool the cabin. I suffered with this for five years.

Finally, just gave it to the mechanic to take a look at it. He evacuated what little was left in the system, pulled a vacuum, and filled it with R-134.

I was quite astounded to see a vent temp of 28°F. at a 60° ambient and it easily holds 40°F. vent temps at 95° ambients, provided that the compressor rpm doesn't drop too low...........in traffic, the vent temp will climb to about 50°F. and the CCU immediately senses the higher cabin temperature and increases the blower speed.

I could only conclude that the system doesn't have sufficient charge............but the pressures don't appear to be off that much............

I took a careful look at the vent temps today.

After starting the engine and getting it above 2000 rpm, the vent temps gradually decreased to approximately 37°F. They remained below 40°F. for the next 35 minutes. Then, without any reason, they began a slow climb up to approx. 58°. Rpm's varied between 3000 and 1000 due to traffic conditions.

After remaining at about 58-60° for the next 20 minutes, they started a slow drop down............gradually reducing until 40° was attained again. The entire reduction was during a period of slow movement.........rpms were typically 1000 or so.........never more than 1500.

So, there's an interesting dynamic occurring with the TXV and it's regulating the evaporator pressure in some fashion.

I'm wondering if the TXV can be the culprit in high vent temps.........insufficient closure?