Proper A/C System Pressure

[Wegner44]

Trying to find the correct system pressure for my 2003 Expedition. I live in Florida and it is 95-100 degrees everyday now. My system will cool but it takes time to get there... I want to make sure my system has acceptable pressure. The engine was idling and the system was set to max cooling while taking the readings.

It is 97 degrees outside now

Low side @ 64
High side @ 235

For a dual zone system what should the proper readings be for this temp?

Any help would be appreciated. If I can save a trip to the shop that would be great!

Thanks,

Rick

 

[stamp11127]

Both are high. What is the static pressure before first running the system? If it has been run, let it balance for an hour then post the low side pressure.

What has been used to recharge it in the past, ac pro or similar that has oil in the can?

Dual zone systems will not change the pressures, they blend hot/cold air to the desired temp settings.

You can use the low side pressure as a general reading of the evaporator temp with the system running. In your case the evap is around 64F - not cold enough.

I recharge to 80% of factory fill and observe the evap temp/pressure then adjust if needed to be slightly above 33F.

 

[Wegner44]

Thanks for responding so quickly!

The static pressure is...
Low - 88 and High - 85

A/C Pro was used the last time refrigerant was added, otherwise, the truck was always taken the shop.

I am relatively mechanical and am hoping this is something I will be able to start doing to save some money down the road.

With the static pressure listed above, what do you think is the next step?

Thanks,

Rick

 

[stamp11127]

What was the ambient temp when you read the static pressure?

This isn't a knock towards a/c pro but there is a problem using it - it adds oil whether you need it or not. Unless you blow a line or component you do not need to replace oil unless it has been removed during the recovery of the system.

For a/c information check out the study guide at the bottom of the page:
http://www.macsw.org/imis15/MACS/Se...spx?hkey=a4bf82fe-9db6-4507-8ddd-27fd9b9153f6

 

[Wegner44]

Sorry missed that, it was about 87 degrees out.

 

[stamp11127]

The static pressure is usually around the ambient temp. Since your readings are higher than normal it can come from one of two things. The high side is leaking into the low side or you have air in the system.
I would evacuate the system and recharge by weight and see what the pressure readings are at that point. Let the vac pump run for at least one hour. Do not add any oil, you may even flush the evap and or condenser and see how much oil comes out. If it is a bunch then the system has too much oil in it.
When putting it back together add one ounce of pag oil to the component that was flushed.

Another reason for the high pressures may be as simple as being overcharged. You still need to evacuate, flush the evaporator and condenser then recharge to proper amount. Once that is complete you will be able to get an accurate diagnosis if there is a problem present.

 

[Wegner44]

Hello,

I am now pulling a vacuum and trying to prepare (if it holds) for the refill of R134A.

On the sticker under the hood of my 2003 Expedition XLT it states 2 different amounts. 1 says for front A/C - 32 oz. and 2 for front & rear A/C - 54 oz.
I assume this sticker was used in multiple vehicles and 54 oz. would be the proper amount.

I just want to make sure before I go and purchase the refrigerant.

Thanks!

 

[stamp11127]

Front and rear is 54oz. Do not get the cans with oil in them. Bleed the air out of the hose before filling the system.

 

[Wegner44]

Alright, so after confirming that the vacuum held and refilling with 54 oz of r134a (bleeding the hose) before opening valve to low side. I am only getting 60 degrees out of the dash vents.

At 93 degrees outside, I am getting readings of 37 on the low and 190 on the high side.

What do you think would be your next step?

Thanks again.

 

[powerboatr]

Alright, so after confirming that the vacuum held and refilling with 54 oz of r134a (bleeding the hose) before opening valve to low side. I am only getting 60 degrees out of the dash vents.

At 93 degrees outside, I am getting readings of 37 on the low and 190 on the high side.

What do you think would be your next step?

Thanks again.

everything above was spot on,

whats your center vent temp on max a/c recirc?
my chart in my gauge says 95F low should be 50-55 and high 275 -300
and suggests your low on refrigerant.