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Pressures not right R12 to 134A

jjrbus on Mon August 03, 2015 10:13 PM User is offlineView users profile

Year: 1993
Make: Toyota
Model: Cab and Chassis
Engine Size: V6
Refrigerant Type: 134A
Ambient Temp: 83
Pressure Low: 45
Pressure High: 225
Country of Origin: Japan

Wish I would have found this site before I started. Have a 93 Toyota pickup. It had a R12 system in shambles so I replaced everything except the hi pressure solid liquid lines, which I flushed and reflushed. I replace all parts with intention of using 134A. I added 7oz of double end capped Super Cool PAG 46 oil as per charts. I failed my first vacuum test found and fixed problem. Pressure tested with nitrogen and it held pressure for 10 hours. Then vacuumed for 1 hour and added 18 oz of Dupont 134A.

I stopped at 18oz and left the system overnight as the pressures seemed to high?

My pressures do not make sense!! With cold engine not started the pressure's are 90 & 90, seems right?

The ambient temp is 83 and humidity is 66%

With engine running compressor engaged but still cold I have 45 Lo and 225 hi vent temp 60

With engine warm I have 100 lo and 250 hi vent temp 60

If I mist condeser I have 55 lo and 250 hi vent temp 58

Left for 10 min with engine running stabilizes at 80 lo and 250 hi vent 60
The charts I have call for 26.5oz of 134A and 7 oz of PAG. The fan seems to be drawing enough air and the engine temp is not rising. This is my first attempt at an AC system and I have no training in AC. So any input would be greatly appreciated. Jim

mk378 on Mon August 03, 2015 10:42 PM User is offline

Go up to 24 oz. You should try to get close to if not at the rated R-12 amount.

You won't get any cooling at 100 psi low. Something is wrong with that reading. You are reading with the manifold handwheels closed, right?

jjrbus on Mon August 03, 2015 10:46 PM User is offlineView users profile

Thanks for the quick response, yes the manifold wheels were closed. Jim

jjrbus on Thu August 06, 2015 6:33 PM User is offlineView users profile

Hey Guys! Took the money pit out for a ride today, just a few miles but needed gas. 50/55 MPH and vent temp at 60° Outside temp 90° Humidity 45%

Note to self tighten all the radiator hose clamps next time to avoid working on vehicle in street! Luckily happened at friends house.

Came home took nap and let vehicle cool off, not cold still warm when begin.

Static pressure was 100 100 Ambient 93° 45% humidity

Start vehicle and 20 / 190 Hi pressure needle is quivering a bit

Let run a bit 30 / 235 Vent 70

Mist 15 / 150 vent 64

Warms up 25 / 200

Increase idle 15 / 150 vent 68

Returns to 30 / 250 vent 72

This seem much more within the charts so decide to add R134A

1oz 30 / 290 vent 66

Add 1 more oz 37 / 290 vent 66

Let set a bit 35 / 275 vent 64

I do not know what happened between yesterday and today but this seem's to be in line with charts?

Should I keep adding a little at a time until I get a lower vent temp?? Jim




mk378 on Thu August 06, 2015 11:02 PM User is offline

You're still undercharged. Also the high side dropping rapidly when you mist means that the condenser fan is not up to snuff.

jjrbus on Sun August 09, 2015 3:44 PM User is offlineView users profile

jjrbus on Sun August 09, 2015 3:45 PM User is offlineView users profile

jjrbus on Sun August 09, 2015 3:54 PM User is offlineView users profile

Have found one problem
? My Toyota is a small RV. I am trying to do this with passenger cab open to RV, cab door open and air set on outside air. I Sealed off RV from truck cab, put air on recirculate and closed truck door's. I do not have pressure reading with me. But outside temp was 80° humidity was 67% and vent temp was 41°. I still only have 20oz in the system and the pressures are a bit under what the charts say.

Will keep an eye on this a bit and see what happens when I drive it. Any thoughts or suggestions? Jim

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