I'd agree with Anthony that 2.8 lbs of R-134a is the right fill for a Fiero conversion system that has been evacuated of old refrigerant and mineral oil. You must also add (from memory) 8 oz of Ester oil when recharging. While recharging by weight is a good way of doing it, I also like to follow the gauges to insure that all is working properly.
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Yep, on a proper AC machine that does all the wizardry, 2.25 lbs as per RWDPLZ a 3800 compressor will make frost on the base of the windshield with the controls in windshield defrost position on a 35 plus degrees Celsius day with the Fiero AC control on Max AC.
I have a 2017 Hyundai Santa Fe, 2015 F150, 2008 Outback, all with recently serviced AC, and my Fiero with a 3800 compressor is the only one that make me cold to the point I have to turn it down.
[This message has been edited by jelly2m8 (edited 07-18-2024).]
My AC works fine for 30-40 min, then it stops working. But if I shut off the car for a few hours and start it, my AC works again
Mechanic thought that maybe we over filled it, and when the gas expands during use, pressure switch is shutting off to protect the system. We used proper AC machine and evacuated old stuff before filling.
My AC works fine for 30-40 min, then it stops working. But if I shut off the car for a few hours and start it, my AC works again
That is weird. When you say stops working, the blower stops blowing at all, or it suddenly starts blowing warm air?
Is the system still using the cycling switch on the accumulator, or is it computer controlled with the donor car's 3 pin switch and the 3800's computer? When doing an R-134A conversion, the cycling switch needs to be adjusted so it kicks on at 21psi instead of the R-12 system's original 25psi.
What type of oil did you use? If PAG which viscosity? Capacity should be 8oz total, no matter the type.
Check the system pressures with a gauge set with the system off for a while and compare to pressure/temperature charts, then see what it's doing with the system running, ~15 minutes into operation, and then when it starts acting up.
Air keeps blowing, but it is warm after 30-40 min of use. AC Compressor is not kicking in
I do have the pressure switched wired into the PCM. AC install was done 2-3 years ago and worked fine, except for minor leak that I could not find so I have to re-charge after each winter
Is 1050g of R134A the correct amount? My mechanic thinks that maybe it is too much, and after using the system, there is too much expansion of gas preventing the switch from turning the AC on
what do you think?
Can you tell me what the high and low pressure "Should" be when AC is working correctly on startup?
Also correct amount of R134A if system is totally evacuated?
If I let the car sit for a few hours and everything is cold, then AC works again
[This message has been edited by cam-a-lot (edited 07-21-2024).]
The original Fiero R-12 capacity is 2.5lbs, which is probably why your mechanic thinks it's a lot, it's more than the vast majority of cars. The R-134A charge should be 80-90% of the original R-12 charge, which would put it around 2.25lbs, or 3 of the 12oz cans you can buy in stores. If he actually has a professional recovery machine and can charge by weight, even better.
Starting with the static pressure: This is with the car off and sitting for a while, high and low sides should read the same pressure, and should be roughly equivalent to the outside temperature. Here's a chart with optimal readings:
You can see from this chart, if it's say 80 degrees F outside, and you're getting a reading of 70, the system is low.
Next, with the car running:
Low and high side pressures should be in these ranges, based on outside ambient temperature.
There are several failure scenarios, which are best explained in this video here:
