'91 300D 2.5 A/C refrigerant quantity question - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 05-30-2014, 08:57 PM

After replacing the core support and the cooling parts (radiator, condenser, fans etc) on my bro's '91 300D from a collision, I went to have the A/C charged today. The car originally had R12, but the core support had a 134a sticker that stated the max capacity for 134a is 2.2 pounds (35 ounces). I am not sure what the capacity of R12 would have been, as the bent core support has been scrapped. Would the later car have any different components than the earlier one that would require more refrigerant? (larger condenser or evaporator?). The system was charged with the 2.2 pounds of 134a, and it seems to have lackluster cooling. I am wondering if it is over charged? Anyone got any ideas?

EDIT: I replaced the Denso compressor with a factory fresh new one, along with the TXV and drier.

ROLLGUY · #2 06-02-2014, 10:31 AM

Anyone? I am taking it back to the shop today, and hopefully he can figure it out. I would have liked to provide more info to him before charging it the first time, but did not have it.

engatwork · #3 06-02-2014, 12:31 PM

I have one sitting in the yard that I can look and see what sticker says when I get home this evening. I suspect that 2.2 pounds of r12 is the correct charge.

JamesDean · #4 06-02-2014, 01:08 PM

My 91 300D 2.5 has a sticker that says 2.2 pounds of R134A.

I have it charged with 2.0 pounds R134A equivalent of "Envirosafe ES-12A Industrial" stuff right now. Cools quite well.

PO had R134A in and it did decently.

TheDon · #5 06-02-2014, 01:18 PM

Quote:

Originally Posted by JamesDean

My 91 300D 2.5 has a sticker that says 2.2 pounds of R134A.

I have it charged with 2.0 pounds R134A equivalent of "Envirosafe ES-12A Industrial" stuff right now. Cools quite well.

PO had R134A in and it did decently.

I wish I had tried the ES-12A I bought instead of using the 134A with my sanden conversion since I have like 8 cans of the stuff. Maybe ill test it out with my 240D and york compressor

ROLLGUY · #6 06-02-2014, 01:28 PM

I just got back from the A/C shop, and they were too busy to look at it. On Friday he put 35 oz (2.2 pounds) of 134a in it, so I suspect that is close. However, driving the car today, several times I heard what sounded like a pressure relief valve on an air compressor. Is there some kind of relief valve in this system? It would be venting refrigerant if that was the case, and I find that hard to believe that they would design something like that as part of the system. Interestingly enough, it now cools much better. I am going back this afternoon, so the pressures will get checked to see if they are anywhere close to spec.

JamesDean · #7 06-02-2014, 01:58 PM

Quote:

Originally Posted by TheDon

I wish I had tried the ES-12A I bought instead of using the 134A with my sanden conversion since I have like 8 cans of the stuff. Maybe ill test it out with my 240D and york compressor

I've had good luck with the stuff so far. My 300D gets pretty cold, even with only the side vents working (center pod is dead). It was 80F the other day up here, I have to roll up the wheel up to keep my arms from cold.

Not the most scientific data. I'll have to get a probe and measure temps or something.

But for $6 a can....I can't complain. I dont have the time, energy, money to convert to 100% R12 and all that good stuff.

We had our fridge service guy out this past week as our one freezer had some problems, he was talking about this stuff as R12 replacement...
http://www.refrigerants.com/hcfc-r414b.htm

Wonder how that would go in cars? Its not cheap! Not as cheap as Es-12A

DeliveryValve · #8 06-02-2014, 02:35 PM

Just for reference..

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ROLLGUY · #9 06-02-2014, 02:59 PM

Quote:

Originally Posted by DeliveryValve

Just for reference..

.

It seems that both are 2.2 pounds for R12 and 134a, but I put 2.2 pounds of 134a in an R12 system. I probably should have only put 80% of 2.2 pounds of 134a in the system. I suspect that IF there is some kind of relief valve, it relieved just the right amount, as it seems to be cooling great now. Either way, I am going back to have it checked this afternoon just to be safe.