A/C Pressure Question

[RFB]

Does anyone know the proper pressures for the A/C refrigerant in a 5030HSTC?

Thanks

 

[KennyV]

There are several variables that you need to consider…
What pressures, High and low side, do you have, along with a few other things will tell if you are close…
1,Ambient air temp 1a,(temp of air over the condenser), 2, Cab return air temp, 3, Evaporator air temp (3a, Is it very humid in the cab while taking an air temp from the evaporator).
Check all of these around 2000 engine RPM.
Insure you have good air flow over the condenser and the blower on the evaporator on high.
Don’t just add refrigerant until you lock up the compressor from an over charge…Post back with as many of these as you can and you should get some indication as to how well it’s working. If there was a simple psi answer to your question, I’d be glad to give it… KennyV.

 

[MrJimi]

LOL, from reading this KennyV, please remind me NOT to mess with AC, what happened to the days of put a can of R-12 and it's cold?

 

[KennyV]

You are so right… R12 is great stuff… things have got way tooooo expensive to use the shot gun approach today… But if you are reasonably careful and watch out for the pitfalls of pressurized anything, it’s still not impossible to make mistakes… LOL… KennyV

 

[MrJimi]

I still have a few cans of R-12 left and nothing to put it in and I hear it's really expensive today. I remember when it was .99 per can? ah, the good ole days, I paid $3.99 for mine, who knew?
being old is not all that good

 

[KennyV]

You are right again…
I’ve been trying out that “being old” stuff for a while now… Definitely makes everything more … … interesting. I still have a car I run R12 in, works wonderful. KennyV.

 

[JRobyn]

A good basic rule of thumb is to add refrigerant (R-134 I assume; check the manual and or stickers on the system) with the system running at a moderate RPM (2000 is good) and cabin fan on high, until the low side pressure coming out of the cabin evaporator is ABOVE the 32 degree saturation pressure. Without looking at my R134 gauges, I THINK this is about 40 psi. The high side pressure should then be about 2.2-2.5 times what the saturation pressure is for the ambient outside air temp. BE VERY CAUTIOUS TO NOT ADD TOO MUCH REFRIGERANT SO THAT THE HIGH SIDE PRESSURES BECOME DANGEROUSLY HIGH!!! If high side pressures go over about 2.5 times ambient, something is wrong, and it may be best to leave it to a pro. If the evaporator pressure is too low, one of two things are likely to occur; 1) the system low pressure switch will cut out the compressor to protect the system from too low of pressure, and/or 2) the evaporator temp will be so low that it will freeze any moisture in the air on the evap coil, quickly rendering the system useless. DISCLAIMER: I know my way around A/C systems pretty good, but I AM NOT a pro, nor EPA licensed!

If you need any more info, post your questions on

Automotive Air Conditioning Bulletin Board :: Index

some pretty good guys on there that ARE pros!

- Jay

 

[DmansPadge]

I still have a few cans of R-12 left and nothing to put it in and I hear it's really expensive today. I remember when it was .99 per can? ah, the good ole days, I paid $3.99 for mine, who knew?
being old is not all that good

Yeah... good old R-12. Now it's really not worth much because there isn't much left that uses it and alternatives like Freeze12 are available. You should have sold it about 5 years ago and got some good cash!!

 

[DUMBDOG]

Does anyone know the proper pressures for the A/C refrigerant in a 5030HSTC?

Thanks

Are you having problems with the amount of air coming out, or is just the temperature coming out warm?

 

[MOPAULY]

Does anyone know the proper pressures for the A/C refrigerant in a 5030HSTC?

Thanks

Information should be on the compressor itself, or on a decal near it. I would think the system would be measured by quantity in ounces or pounds, not pressure, as the pressures will fluctuate based on outside air temperature.

 

[MrJimi]

Yeah... good old R-12. Now it's really not worth much because there isn't much left that uses it and alternatives like Freeze12 are available. You should have sold it about 5 years ago and got some good cash!!

LOL, does that mean that my 8 track tapes are not worth much either?
I keep stuff to long

 

[RFB]

DUMBDOG,

All of the screens/filters are clean, I have installed aluminized bubble type insulation in the cab roof, and the air still does not feel very cold. Cool, but not cold like my pickup truck. I know zero about A/C units, so I am on the step part of the learning curve. The closest dealer/service is 75 miles one way, so I am kind of thinking out loud.

 

[DUMBDOG]

DUMBDOG,

All of the screens/filters are clean, I have installed aluminized bubble type insulation in the cab roof, and the air still does not feel very cold. Cool, but not cold like my pickup truck. I know zero about A/C units, so I am on the step part of the learning curve. The closest dealer/service is 75 miles one way, so I am kind of thinking out loud.

That is what I thought the problem was. In the owners manual for the cab, there is a section that deals with the air conditioner as far as the bubbles in the window on the compressor and how they should look.

I took the top off of the cab, took off the top cover of the heating and cooling unit and blew out the air conditioning and heating coils. Mine were almost blocked.

Another think to check if you are getting good air flow, but the temperature is not quite cold as it should be is to blow out the cooler that is front of the radiator. As soon as mine does not quite cool as it should, that is the first thing that I do, I now do it every fifty hours to stay ahead of the dust in it.

Another thing that will make the a little cooler is to have recirculated air going through the cooler, rather than bringing air in from the outside. I used to bring in fresh air, but after cleaning out the fins on top, the vent in the back of the cab is now in the up position.

Today it was 85 out and it was quite comfortable in the cab and as soon as the clouds covered the sun, the air flow temperature went to low.

I do not think that the air coming out is as cool as a regular vehicle as the area that you are cooling is quite a bit smaller than a vehicle.

 

[JRobyn]

The temp of the air coming out of the evaporator will be almost totally a function of the evaporator pressure (assuming that you have decent air flow over it). What are the current high and low side pressure readings (and the ambient air temp when they are read)? Can't tell much without both current pressure readings.

- Jay