Model: 131 Brava
Engine Size: 2.0 lite
Refrigerant Type: Duracool
Ambient Temp: 78
Pressure Low: 50
Pressure High: unknown
Country of Origin: United States
Hello. I've been working on cars for along time but just recently got interested in air conditioning systems. Maybe I'm getting soft. Maybe because of this hot summer. The plan is to air condition all of my cars.
The first car I've been working on is a 1980 FIAT 131 Brava. I pulled the compressor, condensor and dryer off to free up space in the engine compartment. It sounded like a good idea at the time until this summer. So I put everything back on, changed out the O-rings and pulled a vacuum on the system for about 15 minutes.
The main reason I used Duracool is because they say it's compatible with either R-12 or R134a oil. I did not have the equiptment is remove the R-12 oil. I checked some components as I went along and everything seems to be OK.
I put the first can in and the compressor kicked on and I started seeing bubbles in the sight glass on the dryer. Then with a temperature probe stuck in one of the vents I saw the temperature start to drop.
Eventually the temperature started to rise as the engine heated up. That turned out to be the heater valve leaking through. So I replaced that.
As of right now on MAX A/C, if the ambient temperature is 78F, I'm getting a reading of 59F from the center vents. Not real great but considering all of these components are 30 years old, I think that's somewhat impressive that the system is working. I think if the car was actually moving down the road, the temperature may drop even more. This car is not registered yet so I couldn't take it on a test drive without pulling a plate from one of my other cars.
The blower fan is not blowing as great as I think it should. Probably some resistance in the connectors but I'll work on that.
The size of the condensor and the fan is horrible design. Here's a photo to give you an idea:
OK some questions.
The shop manual says to set the machine at 2 3/4 lbs. Assuming I would have such a machine. Duracool says to add half whatever supposed to go in the system. So I added three cans.
From my understanding if your using a pressure guage while filling the system, 40 lbs means it's full. Correct or is this just a ballpark figure?
While filling the system, if I cracked the low side valve open too much on the guage, the guage would shoot up to 100 lbs. So I backed it off until it was around 40. I'm assuming this was because the pressure in the can was over riding the pressure in the system. Correct?
Next this system has what's known as an Isobaric valve. Which is located between the evaporator and compressor.
The shop manual says if the high pressure switch detects more than 250 lbs (I think that is correct) or the anti frost valve falls to 32F, this valve cuts off flow by 2/3rds. So far it seems under any condition, the wire going to this valve is always engerized. If I unplug this wire, it has no effect on temperature. I tested this valve with a battery and it does in fact work. Anyone ever seen such a valve?
Next question. I'm getting 50 lbs on the low pressure side. Does this mean I overfilled the system even though I supposeably put the correct amount in it?
That's all for now.
After a system has been taken apart and stored open, you need to fit a NEW receiver-drier. The one you have is going to be saturated with water and thus it is useless.
During any charging, etc. on the system you need to be able to measure the high side pressure.
Operating pressures for HC refrigerant are considerably different than R-12 (and no one says what they are supposed to be). Since you have a part that is specifically calibrated for pressure (the "isobaric" suction throttling valve), this system will probably not work properly with anything except R-12. Also Duracool tells you to use a mixture of air and Duracool, air in any system is very detrimental to performance.
Get rid of the Duracool, replace receiver drier, evacuate fully and charge with the specified weight of R-12.
Duarcool I thought we were haivng a BBQ.
Trouble is allot of Fiat part suppliers don't sell A/C replacement parts (not a big demand I guess) but all of these parts had to have come from somewhere else. All of of FIATs used GM and Ford parts. Like GM Smog pumps, HEI control modules, etc.
The hoses are standard sizes and the compressor was made by Sanden. So these parts were made in the USA but question is who made them? So somewhere somebody has to have replacement parts.
The reason I ask about the Isobaric valve is every A/C system I've seen on a car does not use one. Fiats are the only cars I've seen that use this valve. So why would this system require such a valve to restrict refrigerant flow if say a system on my dad's 76 Chevy truck that uses a York compressor does not?
I've got three cans of R-12 but I'm wanting to sell them and recoupe my money on my gauges.
The isobaric valve allows the compressor to run constantly (giving a smoother ride) while it works to prevent overcooling and icing of the evaporator. Late 1960s to early 1970s American designs used a similar system but it was called a POA valve. By 1976 they may have gone to cycling the compressor off with a temperature switch on the evaporator, or the VIR system where the valve is integrated into the receiver tank. The POA and VIR valves were strictly mechanical pressure driven though, they were not electric.
Edited: Mon August 23, 2010 at 8:20 PM by mk378
Wow, I can't imagine there's too many 131 Bravas left! I had one, 1981 I think. A light green 2-door version. A hoot to drive, though being in New England really took a toll on the sheet metal. When both doors rotted out to the point that the latches fell out and I had to chain the doors shut the end was here. It did donate its engine to my 1978 124 Spider, though.
It holds the record as the only car that I have ever owned that a disk brake pad fall off of while I was driving. Yes, it was put on correctly until it fell off.
With that small condenser capacity I think that R12 is going to be the only way to go. Really, it's not that expensive any more and it's readily available in the US. If the system doesn't leak there's no reason not to use R12.
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