[craiggo]

I've done a search or two for A/C stuff here and not found exactly what I'm looking for.

I just replaced my compressor and converted to 134a. However, the temps are nowhere near what they were with r12. After the conversion, I added 3 1/4lbs of 134a (3 1/4lbs of r12) is what the manual calls for. But, it just does not seem to be working quite right (taking into account it won't be quite as cold as with R12).

I thought the low side might need a bit more freon because the A/C would work fine and then suddenly get warm (not real warm, just not as cold) so I figured it was freezing up.

I added 2 more cans to the low side (pressure was about 45 if my gauge works correctly on this system). Now it's even worse...not getting below 60 until I get on the freeway doing 70 and turn the fan down to low.

Any thoughts?

I'm seriously considering going back to R12 (yes I have a BIG can).

Craig /ubbthreads/images/graemlins/shrug.gif

 

[444-4D]

Remove the refrigerant. Pull a good vacuum on the system and recharge with about 2¾ lbs of 134a. What did you do about oil? You don't want too much in there.

 

[FordCummins1]

The conversion instructions for my 92 called for 36 to 44 OZ of R134. The low side I believe was max at 35 psi.

 

[Snotzalot]

Try refilling with Freeze12, it's performance is as good as R12.

 

[perryg114]

I hope you replaced the dryer on the system also. There should be a sight glass on the dryer. When the fluid just stops bubbling it is full with the compressor running. I have done the 134-A conversion and had no problems.

Perry

 

[westbound]

sounds like you're over-charged. low side should be running around 40 and the high should be 100 over ambient temp, give or take a little.
if you go back to 12, you have to change out the oil in the system. you also need to pull a vacuum on the system and walk away from it for an hour or two before refilling w/ refrigerant
there is a new refrigerant out called hot-shot. works on 12 systems with no mods, but is 7.99 a can and just as effective as 12

this is what i'm doing friday.

just for trivia, R134a requires a lot more condenser surface area to be as efficient as R12.

 

[444-4D]

[ QUOTE ]
just for trivia, R134a requires a lot more condenser surface area to be as efficient as R12.

[/ QUOTE ]

A pickup usually converts ok because they have good airflow. There isn't a lot of difference between 12 and 134. At 65-70° the pressure on both is basically the same as the temp. At 250 PSI there is only about 10° difference in temp. The low side is critial to having cold air. You want your evaporator temp right at freezing. This is 28 PSI with 134. With a 45 PSI low side your evap temp is 50°. If you blow 100° air thru a 50° evaporator it isn't going to feel very cold.

 

[94_turbo]

theres aso a diff in the ccot valves in the line--if you pull it back down--go to the ford dealer--and get the ccot for the later truck--that helps a bunch---

 

[craiggo]

Ok, so (as usual) just about everyone's input was right on. I'm way high. 65psi at about 1500rpm. I'm going to try and let a little out without letting the oil out. If that doesn't work I'll use my vacuum pump to zero it out and then I'll add more. The kit I got with my meter in it says that a 134a conversion typically requires 85% (134a) of what R12 was. So it looks like I need a little over 2 cans.

Thanks for the input and I'll report my results.

Craig

 

[ARIZHNT]

I just serviced mine yesterday, I retrofitted it 2 years ago when the compressor siezed. At that time I installed a new compressor, accumulator, swapped the pressure switch to a R134a system switch, and replaced the orifice tube with a later style. I flushed the system multiple times and replaced the seals/o-rings. I evacuated it yesterday and recharged with 2.25# of freon, it was about 1/2 a pound low. Driving home in 106 deg temp the dash was pushing 48-50 degrees. This morning on the way in in 95 deg temp it was pushing somewhere around 30. It does go up at idle, as do the pressures, but there is not much air flow at idle. I have played around with the idea of adding an additional electric fan strictly for the condenser. I'm not fully convinced that it's worth the effort yet, but I am considering it. If anyone else has done this, let me know the results.

 

[craiggo]

So here is the story. I let a ton of freon out of my system. Took me about 45 mintues but it let it out. I let it come out unitl the clutch stopped. Then I added 134 until the clutch turned on and stayed on for about 30 seconds (I think this is the correct amout of time per the dealer repair manual which I will post tonight)and then turned off. Now this system rocks! I get it well below 40 degress on the freeway and at 40 around town. It gets a bit nippleeee if you know what I mean?

Craig

 

[Birken Vogt]

[ QUOTE ]
It does go up at idle, as do the pressures, but there is not much air flow at idle. I have played around with the idea of adding an additional electric fan strictly for the condenser. I'm not fully convinced that it's worth the effort yet, but I am considering it. If anyone else has done this, let me know the results.

[/ QUOTE ]

Most of the pressure increase at idle is due to the fact that the compressor is not running fast enough to really keep up. Hence it can not pull down the low side as low as it needs to go. When running the engine at say 1800 RPM stationary on a hot day you will see the high side pressure go to 300+ while the low side is in the 20-40 range. Then after a while the fan might kick on and the increased airflow might drop the high side to below 250 but the low side stays just the same. But drop the engine back to idle and watch the low side shoot right up there quickly. It is just not designed to cool all that well at low idle.

Birken