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Add R134a or leave alone

Turbofiat on Tue August 24, 2010 4:02 PM User is offline

Year: 1996
Make: Ford
Model: Explorer
Engine Size: 5.0 lite
Refrigerant Type: R 134a
Ambient Temp: 85
Pressure Low: 30
Pressure High: 180
Country of Origin: United States

A friend let me borrow his Interdynamics A/C diagnostic tool to check my 1980 Fiat Brava. The tool said "alert". According to it says I may have too much Duracool in it. But today it seems to be cooling better. I'm getting a 27F drop today and the isobaric valve is not being energized. I still haven't checked the high side pressure yet but will once the car cools down to prevent blistering my hand.

But concerning the Explorer.

I hooked the tool up to it and it flashed "Low charge", So I hooked my guages up. I'm getting 30 on the low side and 180 on the high side.

40.6F on recirc mode and 53F on fresh air mode while iding in my driveway.

This vehicle cools to my satisfaction on recirc mode when it's 97F outside but not so good on fresh air mode. If it's in the 80s, it does OK on fresh air mode.

So just based on these readings, my question is, is it time to add more refrigerant to the system or just wait until the low pressure switch won't let the compressor engage? Or when the it doesn't cool to my satisfaction on recirc mode?

I live in the southeast where it is very humid so I also run my A/C on recirc mode just to dry the air in the cabin.

If the temperature readings sound normal, I'm just wondering if I should start messing with the system or leave it alone for the time being?

mk378 on Tue August 24, 2010 4:35 PM User is offline

If there's any Duracool at all in your Fiat, there's too much.

The tool is just a glorified single gauge -- useless. The only certain way to get a proper charge is by weight.

Turbofiat on Tue August 24, 2010 8:27 PM User is offline

Quote
Originally posted by: mk378
If there's any Duracool at all in your Fiat, there's too much.



The tool is just a glorified single gauge -- useless. The only certain way to get a proper charge is by weight.

I'm trying to track down a used condensor with help from Craig's list. Some guy emailed me and said he had one from a 96 Pontiac Firebird that might fit my Brava (15"high X 25") but he would have to check. So if I go with a larger condensor I'll put R134a in it.

Why is R12 supposed to be better than R134a? is it because you can get away with a smaller condensor and evaporator with R12? So when manufacturers had to start using 134a that had to increase the size of everything?

So if I put a larger condensor on this car, how would I figure up what the new weight would be?

I'll ask again, would putting a larger condensor on a car remove more heat from the refrigerant or would I have to go with a larger evaporator before I'd see a difference? Is bigger better?


mk378 on Tue August 24, 2010 8:39 PM User is offline

Most car systems are ultimately limited by the condenser. New condensers are also of a more efficient design, so even one the same size can transfer more heat. R-12 has a somewhat higher critical temperature than 134a (and HC for that matter). That means that it can still refrigerate effectively at higher internal condenser temperatures. But it is not a miraculous substance that is going to get cold no matter what.

Edited: Tue August 24, 2010 at 8:39 PM by mk378

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