A/C issue after fixing HVAC doors

[upper_tanker]

I feel like I need to start this by saying the only knowledge I have on A/C systems is from what I've figured out along the way of fixing issues on my vehicles. I'm going to try to put as much info here that I can about this issue. Also, to preface this story, the A/C blew ice cold before the blend door replacement, just not through any single vent location very good.

2000 K2500 standard cab, 7.4. The issue is that after I pulled the dash and replaced all 3 HVAC doors, evap core, and heater core, My AC doesn't blow cold after recharging it to 2.0lbs using a Robinaire machine that my dad has. it blows cool, but not cold. Thermometer said 60 degrees. I had to replace the liquid line and condenser due to me stripping the threads on the originals trying to put them back together. Ignorantly, I didn't get a new orifice tube for the old condenser because I didn't notice the old condenser having one so I wasn't sure that's where it even went.

This is the condenser I bought from RockAuto. I see in the info, it says to replace the orifice tube if it isn't integrated. Would this definitely say if it was integrated? it doesn't say either way so I'm really hoping that it is integrated and I have another issue.

More Information for UAC CN4720PFC

I did verify the compressor is kicking on when I have the AC button pressed (also while I have the temp knob on max cold). The button lights up. I pulled vacuum with the machine and let it sit for 10 minutes and I didn't see any leaks. The line from the compressor to the receiver drier is ICE cold, but the connection coming off of the receiver drier going to the evap core is room temp.

I guess my questions are:
1. Any way to know if that condenser I bought/installed has an integrated orifice tube without taking it back apart?

2. If it doesn't have an integrated orifice tube, would having one not installed make the AC blow warm? I will buy and install one if it needs one (if it's not integrated into the condenser), but I need to get to the bottom of this issue regardless.

3. If not having an orifice tube wouldn't make it blow warm, any ideas what else to check next? I'm kind of at a loss since the system has a charge of 2lbs and the compressor is kicking on. Maybe the receiver drier is clogged since it's connection with the evap core is warm?

 

[someotherguy]

You might want to re-read that product page. It doesn't mention an integrated orifice tube, it mentions an integrated drier (accumulator) - you absolutely need an orifice tube in that system. It drops down into the lower line of the condenser. Check the old condenser you removed; you should see the + shaped plastic head of the orifice down in there.

Richard

 

[upper_tanker]

You might want to re-read that product page. It doesn't mention an integrated orifice tube, it mentions an integrated drier (accumulator) - you absolutely need an orifice tube in that system. It drops down into the lower line of the condenser. Check the old condenser you removed; you should see the + shaped plastic head of the orifice down in there.

Richard

Thank you for this. I was about mentally done with the whole job by the time I got to that point so it was my laziness and just not knowing lol. I will order one and install it and hope that's the issue. I appreciate it!

Edited to ask if you know if I'd be better off with the red or white one. Red is under 105 white is over. I live in Michigan so it almost never hits 105 but would the white get it colder?

 

[Schurkey]

My AC doesn't blow cold after recharging it to 2.0lbs

Is 2.0 pounds the correct amount?

I didn't get a new orifice tube for the old condenser because I didn't notice the old condenser having one so I wasn't sure that's where it even went.

Not replacing the orifice tube is a bad idea. The screen on the orifice tube gives you a good indication of the health of the system--little debris caught in the screen is good, heaps of filth and dreck means you need a new compressor and total system flush/replacement.

I pulled vacuum with the machine and let it sit for 10 minutes and I didn't see any leaks.

Not even close to long enough. When it's me, I run the vacuum pump for an hour or more, then leave the system under vacuum overnight as a leak-test. Then run the pump for ten or fifteen minutes the next morning.

There's three reasons to vacuum the system:
1. Removes air
2. Vacuum reduces the boiling point of water. Any moisture in the system boils and is removed by the vacuum pump--IF (big IF) the system is vacuumed long enough.
3. Leak test. System needs to hold vacuum.

The line from the compressor to the receiver drier is ICE cold, but the connection coming off of the receiver drier going to the evap core is room temp.

That's a problem. No way should the receiver-dryer be colder than the evaporator.

I guess my questions are:
1. Any way to know if that condenser I bought/installed has an integrated orifice tube without taking it back apart?

Get a service manual (download from links on this site?) and find out where the orifice tube is supposed to be.

2. If it doesn't have an integrated orifice tube, would having one not installed make the AC blow warm? I will buy and install one if it needs one (if it's not integrated into the condenser), but I need to get to the bottom of this issue regardless.

Without an orifice tube, I doubt the system would get cold at all. Your system pressures would be high on the low-side, and low on the high-side. More-or-less the same pressure everywhere.




When it's my vehicles, I just expect to replace the orifice tube, the dryer, and EVERY O-RING IN THE SYSTEM if I'm doing A/C repairs. Other parts replaced as needed.

 

[upper_tanker]

Is 2.0 pounds the correct amount?


Not replacing the orifice tube is a bad idea. The screen on the orifice tube gives you a good indication of the health of the system--little debris caught in the screen is good, heaps of filth and dreck means you need a new compressor and total system flush/replacement.


Not even close to long enough. When it's me, I run the vacuum pump for an hour or more, then leave the system under vacuum overnight as a leak-test. Then run the pump for ten or fifteen minutes the next morning.

There's three reasons to vacuum the system:
1. Removes air
2. Vacuum reduces the boiling point of water. Any moisture in the system boils and is removed by the vacuum pump--IF (big IF) the system is vacuumed long enough.
3. Leak test. System needs to hold vacuum.

Thanks a ton for your message above. I forgot to reply when I read it, so my apologies. You were right, I put the orifice in and that was the issue. I did end up pulling vac for 8 hours and leaving it sit overnight. My dad has a Robinaire machine so I just used that. I just charged it today and am getting temps of around 46* which is cooler than it's ever been.

Thanks again!

 

[GoToGuy]

You know the forum has the factory service manuals for your year truck to download, it's FREE. It would have answered your basic questions. Provided the knowledge. A plan of action.
Doing it right the first time.
Have access to AC service machine, but not ask questions?

 

[upper_tanker]

You know the forum has the factory service manuals for your year truck to download, it's FREE. It would have answered your basic questions. Provided the knowledge. A plan of action.
Doing it right the first time.
Have access to AC service machine, but not ask questions?

I didn't know that about the factory service manuals.

I mean I just had to swap the condenser, I didn't even think to look inside the tube for an orifice tube because I forgot about the orifice tube. My plan of action was to install a new condenser, and that's what I did. Why would I ask a basic question like how to R&R a condenser? I knew it needed an orifice tube after I was told, but I wanted to also know if anything else could be causing an issue (like the drier).

I'm sorry for not knowing that the forum has factory service manuals, and I'm also sorry for not asking questions even though I have access to an AC machine I guess.

 

[df2x4]

I didn't know that about the factory service manuals.

It's a stickied thread in the "Engine Performance + Maintenance" section, here's a link. Pretty sure we've got all years in there now including '99-'00 classic body style. If you don't see your year available in Hatzie's original post keep scrolling, others have added to the collection in later posts.

https://www.gmt400.com/threads/88-98-service-manuals.43575/

 

[pressureangle]

There's a lot going on here, to be discovered but one thing never changes; a pressure differential always indicates a restriction. If your accumulator is warm going in and cold coming out, there's some sort of restriction in it. The evaporator should be the coldest piece in the system, and the line out to the accumulator should be nearly as cold. Of course hi and low side pressures are needed to make assessments, but you can shoot the low side lines/accumulator with an IR heat gun to get temperature, which roughly correlates to pressure. If you're 60* out of the evap and 30* out of the accumulator on the suction side, that's bad.