Ac temperature cool not cold

[USMC_53]

Hey guys So I just replaced my old ac compressor and the manifold line that goes to the condenser and the accumulator, it had a small leak... once I replaced everything I pulled the all the moisture from the system with my vacuum pump for a about 30 mins then I let it sit for a while and it didn’t loose any pressure. So I went ahead and started the truck turned the a/c on max and went ahead to recharge the system with r134a. I’ve seen that the right amount of refrigerant is 1.6lbs but I could only get about 18 oz in the system before the low side pressure gauge read about 38-40 and the high side read 250! I didn’t want to try and put anymore refrigerant in the system because I thought it was getting pretty high on both low and high side. So I decided to turn the truck on and see how the ac feels... I put a temperature thermometer in the vent and it only gets to 70°f, which feels ok in 105°f weather but not good enough. Anyone have any suggestions, I don’t know what else to check!

 

[Bdsankey]

Following

 

[Trimox]

I am going through the same thing right now. I am assuming you went by the ambient temp chart for R134a? 250 on the high side is on the low side if it is 90 outside. I added a little more to mine the other day when it was 90 out and got it up to 40 low side and 275 high side. From my research my low side is low while I get high side right, tells me I still have air in the system for come reason. I did pull a vacuum but I went ahead and ordered a better pump today to try again.



The only thing I have not replaced on my was the evaporator core and condenser. I did the cabin air filter retrofit a week ago and that helped a little (oh what I cleaned out of there). I am hoping I don't have to replace the evaporator core, that will take a while.


I get my pump Sunday so I will pull a longer vacuum and see how that goes.

 

[zakkb787]

It’s always best to replace condenser and accumulator and the office valve when putting a new compressor in. They can have trash from the system especially if you had a leak. I did all of this and still had a compressor fail because I didn’t take it and have it flushed. Wonder if it’s possible you have a clog somewhere not allowing the 134 to get to the whole system. Just throwing it out there.

 

[Hambone]

As stated by Zack if doing the compressor you should do condenser, accumulator and orfice tube
I’m assuming the old compressor failed?If so you most definitely have crap in the system
First order of business...
If the compressor you put on was not a ACdelco or Denso take it back, Everything else is junk.
When you get the new compressor drain all the oil out and add the correct amount to the compressor itself
You will also need to add some being that your replacing everything else
Flush the lines that you didn’t replace extremely well
Hopefully with the new compressor you didn’t pump any more junk into the evaporator because a blockage in that and your in trouble
Fix those four items and you will be fine
I would also suggest the lowside switch while your there

 

[USMC_53]

Damn Hopefully I didn’t trash this compressor... I’ll have to go get it drained then I think I’ll replace the condenser and accumulator as well, didn’t think of that!

 

[zakkb787]

orifice valve is crucial too.

 

[DAVe3283]

If the system was open for more than 12 hours or so, I would replace the accumulator, or vacuum it overnight. 30 minutes won't pull all the moisture out that accumulated.

This will be a bit long, but I hope it will help you understand what is happening. Or would happen if you had the correct amount of refrigerant. Ideally, the high-pressure refrigerant condenses to a liquid in the condenser, and pools at the bottom. Liquid refrigerant has a much higher thermal density than the gaseous refrigerant coming out of the compressor and in the top half of the condenser. So most of the heat extracted from the condenser actually comes from the liquid refrigerant, not the gaseous refrigerant.

Since you didn't fill enough, there isn't much (if any) liquid R134a in the condenser, so very little heat is removed from the refrigerant. This results in the liquid being much hotter than it should be, in turn resulting in the high low-side pressure after the orifice tube. The refrigerant is still hot. This is why you get 70° air out the vents.

The other problem I see is you listed 1.6lb as the capacity, but my service manual shows 1.8lb for a 2001. And you only have 1.1lb in the system, so about half what you need. Put another 10-14 oz in the system (up to 2.0lb works well in these trucks).

At 90°F outside, a low-side pressure of 40-60 PSI is considered normal, and a high side pressure below 300 PSI is also normal. I bet it stays below 300 PSI as long as you have good airflow through your radiator. The ECU will disable the compressor if the high-side pressure goes too high, I think around 400 PSI.

As for the compressor, most come with an "average" amount of oil, and you shouldn't have hurt it. If you replace the accumulator, that can hold a lot of oil, and you should measure how much comes out, and put that much new oil in the new accumulator. Ideally you do the same when you replace the compressor. Since you've run the new compressor, oil will have migrated around the system, and you don't really know how much you have anymore. You can drain all the oil from the system then flush it, and start with the GM spec, or realistically, just add an oz or 2 (max) and you will probably be just fine.

If your previous compressor failed, I strongly recommend replacing the condenser, accumulator, orifice, and liquid line as well as the parts you already installed. The debris will pile up in the condenser, liquid line, and orifice tube and result in high high-side pressure and very low low-side pressure. Since your low-side pressure seems OK, you might have been lucky. Did the compressor grenade, or have a clutch failure? If the compressor was working internally (like a simple clutch or bearing failure), then the system is still clean inside, and you can relax.

 

[USMC_53]

My old compressor had a clutch failure, I couldn’t even spin it by hand, hopefully I can get away with replacing everything! I’m about to order all the stuff now! I’m not too familiar with the a/c system, what exactly is the liquid line? And as far as the oil in the accumulator, when I go to replace it you said I should add 1oz to whatever amount comes out of the old one ?

 

[DAVe3283]

My old compressor had a clutch failure, I couldn’t even spin it by hand, hopefully I can get away with replacing everything! I’m about to order all the stuff now! I’m not too familiar with the a/c system, what exactly is the liquid line? And as far as the oil in the accumulator, when I go to replace it you said I should add 1oz to whatever amount comes out of the old one ?

If the old compressor didn't break inside and send debris out, you don't need to replace everything. If it did send debris out, or you aren't sure, it is usually best to replace everything except the evaporator (the inside the cab part, because it is a giant pain to get to). The reason I recommend replacing the condenser & liquid line is they are relatively cheap and VERY difficult to flush debris out of successfully. Why risk a new compressor if something were to dislodge you didn't manage to flush out?

The liquid line is the metal line from the condenser at the front of the truck along the fender to the evaporator (the bulkhead at the firewall). It has the orifice tube inside it. New liquid lines usually come with a new orifice tube already installed, which makes things easy. It is called the liquid line because it carries the liquid (well, we hope it is liquid) R134a from the condenser to the evaporator.

And if you aren't going to flush the system, then yes, I would put 1-2 oz extra oil plus the amount that comes out of the old accumulator into the new one. If you are going to replace the condenser and liquid line, you are really only one step away from a full flush and adding the correct amount of oil, then you know you're good.

New condensers come with no oil in them (everything but the compressor usually ships dry). So if you are replacing everything, you might as well drain your compressor of all its oil, throw away the old accumulator, condenser, and liquid line. Now take a container of AC flush and flush the evaporator core backwards (from the suction line port pushing the flush out the liquid line port). This will remove any debris that made it past the orifice tube. Do the flush again forward, then finally just use clean dry air and try and remove most of the flush by airing it out both ways. It wouldn't hurt to run some flush through your new suction/discharge lines & manifold. Now add the OE amount of oil to each component as you assemble it, then vacuum it well to boil off remaining flush. I would go at least an hour, or overnight if your vacuum pump can handle it.

I attached the capacities table from GM Techline.

 

[USMC_53]

Ok great man!! I appreciate all your help, I’m gonna go ahead and replace all those parts just to be safe like you said! Now with the new accumulator is there a factory capacity I can fill it to? Just to make sure I have all the right levels of oil in the whole system. The chart just says add 2oz to what came out of the old one, how do I know if the old one has the right amount? I just Don’t want to do this a third time after I get everything installed lol

 

[zakkb787]

Ok great man!! I appreciate all your help, I’m gonna go ahead and replace all those parts just to be safe like you said! Now with the new accumulator is there a factory capacity I can fill it to? Just to make sure I have all the right levels of oil in the whole system. The chart just says add 2oz to what came out of the old one, how do I know if the old one has the right amount? I just Don’t want to do this a third time after I get everything installed lol

I would have had to do it a third time if I kept the truck, and I did all this. Install the parts. Take it to a shop. Tell them you want a flush and fill. You can still have a ton of carnage in the evaporator. Vacuum does not do anything for this. Plus, if you order your compressor online, no one will warranty it without proof that a proper flush was done.

 

[zakkb787]

https://www.duramaxdiesels.com/forum/showthread.php?t=77198

Read through this. It’s my old thread. Pay close attention to what FERM and Chevy says.

 

[USMC_53]

Alright guy so I did everything swapped out the condenser, accumulator, new orifice tube and line, new low pressure switch, flushed the evaporator with ac flush, used the ac flush on the new lines as well. I filled everything up with the recommended pag oil in accordance with the gm techline! I pulled vacuum for 8hrs, I was able to fill the system up with 30oz of r134a. Low side pressure was about 60 and high side was at 300! Looks a lot better but...... the temp is still at 70° but when I drive around it will drop to 60° it’s a bit better. Not sure what else Am i missing?

 

[Chevy1925]

Alright guy so I did everything swapped out the condenser, accumulator, new orifice tube and line, new low pressure switch, flushed the evaporator with ac flush, used the ac flush on the new lines as well. I filled everything up with the recommended pag oil in accordance with the gm techline! I pulled vacuum for 8hrs, I was able to fill the system up with 30oz of r134a. Low side pressure was about 60 and high side was at 300! Looks a lot better but...... the temp is still at 70° but when I drive around it will drop to 60° it’s a bit better. Not sure what else Am i missing?

whens the last time you pulled/replaced the cabin air filters? are you checking temp with recirc on and a/c button on, blower speed at 5 and running truck at 1500-2k rpm?

 

[USMC_53]

They are fairly new man. And yup got the ac on recirc, air on 5 and ac button is lit! I’ll hold the rpms as well! I’m stumped

 

[Chevy1925]

your pressures are not far off. mine was 40/225 in a 90* garage. at 105*, you should be experiencing higher pressures, specially at idle and no fan on. How are you measuring vent temp? ill measure mine when i get home but 60* doesnt sound far off considering outside temp. Thats assuming interior temp is 100*ish.

 

[USMC_53]

I’m using a regular vent thermometer! Yea it might be because it’s been super hot! I just remember that the ac used to be very cold before!

 

[DAVe3283]

The pressures are in the ballpark. You should be hearing your fan start to engage if you rev it up or are driving it around. On all 3 of my LB7s, the A/C will throw enough heat off to engage the fan after a minute or two of city driving. If your fan isn't engaging, it might be time for a new fan clutch.

I run a Hayden with a slightly lower than stock engage temperature, and it works well, and I have heard good things about the Kennedy clutch too. But even the OEM clutch on my brother's truck will kick on from A/C in 90°+ weather.

Compare the outside temperature and see if your pressures are in this range:

Based on the pressures you report, if you are in ~100°F weather, that's where they should be. Just make sure your cooling fan is kicking on. I know I can feel the A/C cool off in my truck the moment the cooling fan engages. The A/C condenser has to be able to dump the heat to the atmosphere, so the more air it gets, the better it works.

 

[Bdsankey]

The pressures are in the ballpark. You should be hearing your fan start to engage if you rev it up or are driving it around. On all 3 of my LB7s, the A/C will throw enough heat off to engage the fan after a minute or two of city driving. If your fan isn't engaging, it might be time for a new fan clutch.

I run a Hayden with a slightly lower than stock engage temperature, and it works well, and I have heard good things about the Kennedy clutch too. But even the OEM clutch on my brother's truck will kick on from A/C in 90°+ weather.

Compare the outside temperature and see if your pressures are in this range:

Based on the pressures you report, if you are in ~100°F weather, that's where they should be. Just make sure your cooling fan is kicking on. I know I can feel the A/C cool off in my truck the moment the cooling fan engages. The A/C condenser has to be able to dump the heat to the atmosphere, so the more air it gets, the better it works.

This is good info. I know I'm fighting an issue where my truck decides to just keep the AC clutch engaged even after I turn the AC off, switch positions, switch temps etc. Only a hard key cycle will reset it.