Hello

What is the correct amount of R134a going itnto a Fiero with 3800 motor?

I have searched old threads, but there seem to be too many opinions

Can someone with knowledge and experience pls reply?


thanks]

quote Originally posted by cam-a-lot: Hello What is the correct amount of R134a going itnto a Fiero with 3800 motor? I have searched old threads, but there seem to be too many opinions Can someone with knowledge and experience pls reply? thanks]

what compressor? is it the stock fiero one or not?

2.25 lbs

RWDPLZ always has solid advice in regards to the Fiero AC system.

[This message has been edited by jelly2m8 (edited 07-14-2024).]

hello i am using the 3800 compressor

so 2.25 lbs is the consensus?

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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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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).]

Thanks. That is how much I put in. 1050 grams

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.

Any idea why AC may stop working after 30-40 min?

quote Originally posted by cam-a-lot: 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.

RWDPLZ

thanks for jumping in

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:

Perfect, thanks everyone.

Thanks for providing the pressure info

Should this be checked with the engine NOT running?

I am getting a P1641 AC Clutch Relay Control Circuit code and my AC compressor is not kicking in

I plan to check the power going to the compressor and the the switch on the AC line, but am wondering if maybe I have too much refrigerant, and on hot days like today, I have too much pressure in the system and it doesn't turn on because of this

Would like to check pressure using my friend's AC machine, just need to know if reading should be made with engine on or off. If engine off, should it be cold?

quote Originally posted by cam-a-lot: Thanks for providing the pressure info Should this be checked with the engine NOT running? I am getting a P1641 AC Clutch Relay Control Circuit code and my AC compressor is not kicking in I plan to check the power going to the compressor and the the switch on the AC line, but am wondering if maybe I have too much refrigerant, and on hot days like today, I have too much pressure in the system and it doesn't turn on because of this Would like to check pressure using my friend's AC machine, just need to know if reading should be made with engine on or off. If engine off, should it be cold?

A/C pressure is checked with the engine running and the blower on high. An excessive charge will turn off the system as the pressures will exceed those shown in the chart above, The ranges shown there are correct.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

First chart above is with the system off and hasn't been on in a while, second chart is while running.

In a totally unrelated note, the air conditioning n my apartment died today, system blows but not cold. When the apartment people refused to answer their phone, I went out side and found the capacitor blown at the condenser. Got it fixed an hour later, after the maintenance guy tried gaslighting me about not reading the thermostat properly (I think they're starting to run low on R-22 and don't want to charge their leaky 25 year old systems more than necessary).

Thanks guys... Last night I hammered the gas and pretty sure I snapped the joint inside one of my axles.. So AC will have to wait until I get this fixed. My F23 has been bullet proof, but the remaining weak link is the axles. crap..

thanks for the advice