Charge Rate for regas - Alfa Romeo Bulletin Board & Forums
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post #1 of 3 (permalink) Old 12-09-2016, 09:00 PM Thread Starter
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Charge Rate for regas

The installation of the AC in my 105 GTV 2000 uses the original factory Borletti Evaporator yet has a modern Sanden 508 Compressor and Parallel flow condenser. The installation is shown here:

It has been nearly 3 years since I had the system serviced and it has lost its cool somewhat. I suspect a regas is in order.

I was reviewing the literature on Alfa's original charging instructions for the FREON and they recommend 1kg of FREON to charge the system. This was for the original factory installation back in the 1970s.

My mechanic charged my system with 560 grams of R143a back in 2013.

What are people's thoughts on the most appropriate quantity of R134a to use to charge the system? Should I stick with 560 grams of R134a or are there advantages (and presumably risks) to using a larger quantity R134a?

I rarely don't know what kinds of pressures the system can hold.
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post #2 of 3 (permalink) Old 02-01-2017, 09:50 AM
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I don't have experience with a custom setup like yours, but generally speaking conversions from R12 to R134a call for charging the system with R134a at 80% of the quantity of R12. So in your case, 800 grams (assuming the recommended R12 quantity is correct).

That, however, is a general guess. I would start with 600 grams and see what vent temps you get, then add a little at a time, wait and check vent temps again. Stop if you're not lowering the vent temp. Again, generally speaking, a little too little is better than too much, as far as efficiency goes. Hopefully, the oil type and quantity in the system is correct. Too much oil hurts the efficiency of the refrigerant.

From my personal experience doing a conversion on a '91 (R12) 164, the 80% figure was a little low, IMO. The 80% rule of thumb would call for 36oz of R134a, but I found through experience, that about 40oz worked a little better.

Also, unless the hoses you used are R-134a barrier hoses, you can expect a yearly loss of refrigerant and a top-off required at the beginning of the cooling season.

John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 02-09-2017 at 09:34 AM.
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post #3 of 3 (permalink) Old 02-01-2017, 12:37 PM Thread Starter
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Hey thanks for this - I was never aware of this guideline. I had it charged only a few days ago with 560 grams of R134a and it seems to blow pretty cold so maybe that's enough but I will keep your advice in future for next time.
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