83 240d condenser capacity question - PeachParts Mercedes-Benz Forum

Caseyc · #1 09-28-2019, 10:25 AM

I finally got around to overhauling my AC. I replaced a faulty R4 compressor with a new 4 seasons R4. I also replaced the OEM condenser with a 16x20 parallel flow and neccessary hoses. A new drier and TXV, and a 126 fan in place of the smaller original. I flushed, nitrogen tested and vacuum tested before adding 3 12oz cans of r12. I intended to add 4 cans or as close to 2.9lbs as I could get, but I noticed after the 3rd can, the compressor is running smoothly and NOT cycling, and there are no bubbles in the site glass on the drier.

Cooling is sufficient, ambient temp is mid 80s with high humidity.
Lo is reading around close to 50 and Hi around 175.

Is it possible that the condenser capacity is reduced from the OE condenser, causing 36oz of R12 to be suitable? Should I stop here or add more?

Best regards

Diseasel300 · #2 09-28-2019, 10:40 AM

A parallel flow condenser will hold significantly less gas than a series or serpentine tube coil will. Your total system charge will be significantly less than factory.

A trick that works with an unknown charge level is to open all doors on the car, fan on max speed, temp dial on max cold. Stick a thermometer in the center vent. Add gas until the temp coming out of the center vent is ~25˚F below the ambient temperature (if it's 85 outside, you're looking for 60). Keep SLOWLY adding gas and pausing [1-1.5 mins] after each addition until you reach 30˚F below ambient. Glacially slowly (with long pause [2-3 minutes] between additions) add gas until you stop seeing any sort of change in discharge temp. If you're slow adding gas and give the system time to equalize after each addition, you'll never be wrong if the system is healthy. Keep an eye on your gauges, if something looks off, it probably is.

The big fan and PF condenser will drop your head pressures a fair bit compared to the old series/serpentine coil. If the fan is not being controlled by head pressure or refrigerant temperature you may encounter poor cooling performance in lower ambient temperatures.

ROLLGUY · #3 10-01-2019, 09:17 PM

Quote:

Originally Posted by Caseyc

I finally got around to overhauling my AC. I replaced a faulty R4 compressor with a new 4 seasons R4. I also replaced the OEM condenser with a 16x20 parallel flow and neccessary hoses. A new drier and TXV, and a 126 fan in place of the smaller original. I flushed, nitrogen tested and vacuum tested before adding 3 12oz cans of r12. I intended to add 4 cans or as close to 2.9lbs as I could get, but I noticed after the 3rd can, the compressor is running smoothly and NOT cycling, and there are no bubbles in the site glass on the drier.

Cooling is sufficient, ambient temp is mid 80s with high humidity.
Lo is reading around close to 50 and Hi around 175.

Is it possible that the condenser capacity is reduced from the OE condenser, causing 36oz of R12 to be suitable? Should I stop here or add more?

Best regards

The sight glass is your friend if you are using R12. If no bubbles in the sight glass, you are golden. No need to add more refrigerant. The last R12 and PF system I did took about 24 ounces.

vwnate1 · #4 10-01-2019, 10:54 PM

Both are good methods, I now some times get a 40 degree temperature drop on my 240D with the SANDEN and PF condenser .

As mentioned, s l o w l y add the Freon and allow lots of time for the system to neutralize between adding .

Using the least amount makes the system work better and less strain on everything .

Getting the AC in shape for Winter is great because your defroster uses it to work much faster / better .