Air conditioner: High and low side pressure

[TN-W124 Diesel]

1993 300D: what should the low side pressure and high side pressure be with compressor running? mine is at 40 low side (blue hose) and 225 psi (red hose) on high side? is this normal?

[dannym]

What was the ambient temperature? that will be the most important defining factor.
If you do a google search for Refrigerant Temperature Pressure charts I'm sure you'll find something.
Also:
Was the engine at idle or 1500 rpm as recommended?
Did you have the auxilliary fan running?

Danny

[TN-W124 Diesel]

Originally Posted by dannym

What was the ambient temperature? that will be the most important defining factor.
If you do a google search for Refrigerant Temperature Pressure charts I'm sure you'll find something.
Also:
Was the engine at idle or 1500 rpm as recommended?
Did you have the auxilliary fan running?

Danny

yes the aux fan was running, engine at idle thanks

[dannym]

There's a chart here:

http://www.ackits.com/index.cfm?fuseaction=Chart

The pressure should come close to matching the outside air temperature.

What temperature were you getting out of the vents?

Danny

[leathermang]

It needs to run at that high idle at least 10 minutes to get things stabilized and moved around in the system... for accurate readings...

[Hit Man X]

Originally Posted by dannym

There's a chart here:

http://www.ackits.com/index.cfm?fuseaction=Chart

The pressure should come close to matching the outside air temperature.

What temperature were you getting out of the vents?

Danny

This may sound silly but I'm still reading on A/C recharging, I'd assume Low side will increase accordingly to High side? So if my High side is correct my Low side should also (all else being equal)?

Also, what's the best way to monitor ambient temps outside?

[dannym]

Originally Posted by Hit Man X

This may sound silly but I'm still reading on A/C recharging, I'd assume Low side will increase accordingly to High side? So if my High side is correct my Low side should also (all else being equal)?

That's true to a point. without getting too technical these systems are designed with a specific charge to achieve the desired pressures. So yes, If your charge is good then your high and low sides will be right.
Of course other things can come into play that can cause innefficiency.

Originally Posted by Hit Man X

Also, what's the best way to monitor ambient temps outside?

This is right from the chart link I gave you:
R-134a PressureTemperature Relationship Pressures shown in the charts are provided as a general guide and may not represent your exact readings. Ambient temperature is measured 2 inches in front of the condenser.
Go to the nearest hardware store and buy a $2.00 dial thermometer.

Danny

Originally Posted by Hit Man X

This may sound silly but I'm still reading on A/C recharging, I'd assume Low side will increase accordingly to High side? So if my High side is correct my Low side should also (all else being equal)?

Also, what's the best way to monitor ambient temps outside?

Uh, you might try using a thermometer.

You should be measuring ambient within a few inches of the condensor.

Parameters necessary for system evaluation. First run at 1500 RPM with a/c max and fan high.

Low side
High side
Ambient temp
Vent temp

With this information and access to the p/t chart FOR YOUR MODEL CAR, the system performance can usually be analyzed.

Have a great day,

[Hit Man X]

Well yes a thermo, but I meant do you just hold it infront of the condensor to get the temps or what...

[dannym]

Bend a wire hanger to hold it for you. A little duct tape may be in order.
You don't want to be standing there holding it. There are better things to be doing.

Danny

[Robert W. Roe]

Isn't the outside air temperature sensor somewhere between the bumper and the AC condenser?
I had 91 degrees indicated and 40 psi low side when I topped off my 300TE this afternoon.
I imagine that ambient temps climbed a bit due to idling for a while tho....

No, use a dial thermometer and just put the probe shaft down into the vent. You can get a dial thermometer for about $5 at the auto supply.

Good luck,