How many pounds of freon do I need??

[Deville]

I checked the AC on my freightliner today the guage said it only had 7 pounds of freon in the system. It blows coild but could be colder. I thought the guage was wrong so I checked my Van & it had 30 pounds of Freon the guage was dead cente rin the green which is fine by me.

I don't wanna over fill the system in the Freightliner. I just had major AC work done so I know it's not leaking. I think my mechanic aired on the side of caution & underfilled the system to make sure none of the older seals were going to blow out.

Anyway, how many pounds? I have a 60 inch x 72 inch sleeper but all the vents blow out of the dashboard.

 

[davekc]

Something doesn't sound right. Our KW's and Fruitliners only hold 3.5 lbs to 4.5 lbs depending on the truck. I don't think you could get 30 lbs of freon in a van. Should be a sticker on the compressor for the amount, or.....call a deaer with your VIN and they will tell you how much. If you have too much, it works the other way. It will degenerate your AC. It could also cause a failure at the compressor because the pressure is too high.

 

[FlyingVan]

I think he is talking about psi, not pounds of freon.

Btw, I don't know the answer.

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[davekc]

Pounds of freon is what he needs to know. Pressure is of value but it depends on where it is being tested. That is needed to determine if the high pressure valve/switch is opening. Trucks with a sleeper will have two if the bunk has a AC unit.

 

[purgoose10]

To much freon will kill a system faster than none.

 

[Deville]

Hmmmmmmmmm Perhaps I was wrong. I'm in the safe green zone on the van. Maybe that is PSI I have to look at the guage again. On the truck it wasn't anywhere near the green it was just under 7. I will check it again in the morning. Maybe it was good.

This is why I asked before I added more.

 

[zorry]

I know nothing about A/C other than I want it to work.
I heard Homer from TA state today that the ac should only cool the air 20degrees. If it's 95 outside, you should be happy with 75 at your vents.
I would have expected more cooling capacity.

 

[Deville]

Pounds of freon is what he needs to know. Pressure is of value but it depends on where it is being tested. That is needed to determine if the high pressure valve/switch is opening. Trucks with a sleeper will have two if the bunk has a AC unit.

No Bunk AC.

 

[Deville]

My guage looks like this.

It is PSI. D'oh!

Reading Car AC Gauges - Bing Images

Anyway, the truck guage was around 7psi.

 

[BobWolf]

AC work can be verry expensive and hazardous if you dont have the right tools and equipment. If your not sure, contact the mechanic that did the repair in case he missed somthing. He will be able to tell you how much he put in as well as what he set it at. Most states require H.V.A.C. companies and A/C mechanics to track refridgerant due to EPA regs. Everything from where and how much they purchase, install, reclaim and disposal and its based on weight.
I would also check with the dealership for required settings.

If you attempt to add freon at your own risk follow the ONE CAN 12 oz rule. If it dosent do the trick find a shop.
Also ues e calibrated dial thermometer to check temms at the vents. 20 deg.F drop.

 

[Deville]

AC work can be verry expensive and hazardous if you dont have the right tools and equipment. If your not sure, contact the mechanic that did the repair in case he missed somthing. He will be able to tell you how much he put in as well as what he set it at. Most states require H.V.A.C. companies and A/C mechanics to track refridgerant due to EPA regs. Everything from where and how much they purchase, install, reclaim and disposal and its based on weight.
I would also check with the dealership for required settings.

If you attempt to add freon at your own risk follow the ONE CAN 12 oz rule. If it dosent do the trick find a shop.
Also ues e calibrated dial thermometer to check temms at the vents. 20 deg.F drop.

I wouldn't even put that much in. I think i'll just leave it alone. The lines that go under the dashboard that run along the fire wall actualy have ice forming on them. Not sure if that's good or bad.

 

[zorry]

Even though it's a Freightliner,I doubt it was designed that way.

My guess: BAD.

When you figure it out, let me know. My wife wants an ice maker in our truck.

 

[davekc]

Ice forming usually isn't a good sign. That is a indication of low freon. Same as a condensor freezing up in say your house. I don't subscribe to a 20 degree variance. You wouldn't on a car. TA guy is wrong. Who would buy a car that only cooled to 70 degrees when it is 95 out?
At 95 degrees, it should be blowing around 54 degrees at the vents.

 

[Deville]

Ice forming usually isn't a good sign. That is a indication of low freon. Same as a condensor freezing up in say your house. I don't subscribe to a 20 degree variance. You wouldn't on a car. TA guy is wrong. Who would buy a car that only cooled to 70 degrees when it is 95 out?
At 95 degrees, it should be blowing around 54 degrees at the vents.

I would think that 7-9 psi on the guage is on the low side.

 

[Monty]

Sounds to me like you need an expert on a/c ....... and one thing I do know, vacuuming the system to remove moisture is extremely important.

One of those di-electric a/c units will lower the temp 20 degrees from the ambient temp. As they start cranking down, they can get mighty cold! Used one on a pop up camper, took time to cool, but is sure did a good job!

 

[Deville]

I added about 6 oz's to the system today & the PSI's are just under 10. It was the same temp today as yester 80* & I was much more comfortable today than yesterday. I'm still iceing up on that one pipe by the dashboard but everything is working. The compressor is cyceling normally. The air is cold. So i'll just take it day by day. I'm sure it's still on the low side. From everything i'm reading it's better to be a little low than too high & run the risk of blowing the system out. Although i'm pretty sure if there was too much freon in the system it would shut it self down. There should be a pressure valve cutoff by the dryer.

The problem with these autozone type of systems is that they only addresses the low side of the system. There should be a high side guage as well.

My way of thinking right now is even bad AC is better than no AC.

 

[skyraider]

Ice forming usually isn't a good sign. That is a indication of low freon. Same as a condensor freezing up in say your house. I don't subscribe to a 20 degree variance. You wouldn't on a car. TA guy is wrong. Who would buy a car that only cooled to 70 degrees when it is 95 out?
At 95 degrees, it should be blowing around 54 degrees at the vents.

In my days as a HVAC tech, 45 to 55 degree cool air from the supply vents is the range you need. Most autos and trucks usually hold up to 3.87 lbs of R134A freon. Now that said, I would recommend you take your ride to a hvac place and have them pull a vacuum on you system for 10 minutes, then they should stop, wait and see if your system has no more then a 3 to 5 micron rise in pressure, then refill system to proper lbs of freon....u should be good to go. PS: Sometimes nuisance losses of freon is in O-rings in your system, a simple fix by a tech.

 

[Jenny]

I know nothing about A/C other than I want it to work.
I heard Homer from TA state today that the ac should only cool the air 20degrees. If it's 95 outside, you should be happy with 75 at your vents.
I would have expected more cooling capacity.

I would beg to differ with Mr. Homer. At one point in our trip yesterday our thermometer, dash guage, and phones read over 120° . It was one of those things that we stopped to take a photo of for rememberance.
Granted our truck was not ice cold inside like normal, it was at least 40°-50° cooler, if not more. I slept covered with our comforter.

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[zorry]

I totally agree. 50 out of the vent sounds right to me.
Maybe it's a CYA thing. If they can get you 20 degrees, they will say, "Your are in spec." good enough.