AC specs check

[Porno Joe]

07 LBZ in my sig.

I rubbed thru my AC line by my pass wheel well last year and lost all my freon. I replaced it and recharged- I accidentally overfilled so I just drained some back out.

Now today I think I was under charged- driving thru town with AC on all of the sudden the air would get real hot- I'm guessing the low pressure switch was kicking compressor off.

I threw my gauges on and checked. Seemed low so I tossed a bit of 134 in. Here are my specs now. It's 90 and humid in my garage

At idle:
Low side 35( I originally charged to 40 after several cycles it settled at 35-36)
High side 225
AC on full blast thermometer in center vent read 58- so I got a 32 degree drop.

After settling psi settles around 100

Cooling stack is clean and it will suck a piece of paper and hold it to it.

This sound like it's in spec?

 

[Chevy1925]

run the truck up to 2k rpm and turn "max a/c" on (recycle inside air and a/c button on), blower on high.

looks low to me, specially if idling. high side ought to be around 275ish and low side closer to 45ish but only once the mechanical fan kicks in. high side will go pretty high on pressure before that fan finally kicks in so dont freak out. ive always done 2 full 12oz cans plus a half can and it always comes out spot on.

 

[Porno Joe]

Ok I don't have the mechanical fan- got flexalites in. Got em wired to run when the ac comes on.

I had the truck Rpms at 1500 with ac set on high and recycling when I took the temp readings. But at idle when I got out to check pressures.

So at idle with my electric fans running I should want to be closer to 45?

 

[Chevy1925]

At 2k RPM it should be. I do not go off idle cause your a/c is not designed to be the most efficient then.

 

[bmc1025]

If you are using electric fans I would only rev to 1500, the high side pressure will likely skyrocket using only electric fans. Roll all Windows up except driver's, set it to max A/C and fan on high. Watch your thermometer and slowly add refrigerant , you will know you are overfilling if the temperature goes up. At 90 degrees you will be closer to 45 on the low side. You should be able to get your outlet temp into the 40s.

 

[Porno Joe]

Ok checked pressures tonight. I tried to add some freon but my can was just about empty

It's only 75 in my garage today.

Static truck sitting pressure was around 90

Low side- 29 at 1500-2000 rpm
High side- 230 at 1500-2000 rpm

My shitty vent thermometer never dropped below 54 degrees.

My chart says at 75 degrees my low side should be 35-40. That sound about right?

 

[Chevy1925]

at 75 degrees, yes. pressure will increase as temp increases

 

[Porno Joe]

Ok so I need to pickup a can of 134 tomorrow. I'll add till I'm up to 35. Start on the low end.

 

[bmc1025]

After you replaced the condensor did you pull a vacuum before refilling?

 

[c20elephant]

R134a systems are charged by weight of the refrigerant and oil not pressures, too little or too much can cause erratic behavior.

 

[Porno Joe]

After you replaced the condensor did you pull a vacuum before refilling?

yes pulled a vacuum on it last year. Actually pulled it several times because I thought my vacuum pump wasn't working correctly.

 

[bmc1025]

R134a systems are charged by weight of the refrigerant and oil not pressures, too little or too much can cause erratic behavior.

In a perfect world yes, these trucks have simple systems and can be fairly easy to charge by pressure/temperature. Systems with variable compressors and H blocks or TXV can be a pain.

 

[Porno Joe]

R134a systems are charged by weight of the refrigerant and oil not pressures, too little or too much can cause erratic behavior.

yes the fill spec is for pounds but in my case- where I initially overfilled and then pulled to much out, I have no way of knowing how many pounds I have in the system. unless I fully evacuate it and start over.

So I use the pressure readings of the AC system to determine if you are over or under filled. I'm by no means an expert on AC which is why I posted here to confirm my low side readings. I believe the weight fill spec is based on the size of the vehicles system, where as the psi readings are the general rules for any AC system, regardless of make.

 

[mike diesel]

In a perfect world yes, these trucks have simple systems and can be fairly easy to charge by pressure/temperature. Systems with variable compressors and H blocks or TXV can be a pain.

I know all about that TXV

It failed on my house AC, evaporator looked like Antarctica!

 

[bmc1025]

I know all about that TXV

It failed on my house AC, evaporator looked like Antarctica!

I broke a line on a house AC unit once and repaired it myself. I then called out a friend of mine to recharge the system, he was having all kinds of problems getting it filled. Long story short it was a ball of silver solder stuck in the TXV. Sometimes I wish I wasn't so DIY.

 

[Awenta]

I broke a line on a house AC unit once and repaired it myself. I then called out a friend of mine to recharge the system, he was having all kinds of problems getting it filled. Long story short it was a ball of silver solder stuck in the TXV. Sometimes I wish I wasn't so DIY.

Supposed to be brazed

And yes, they are a pain. You have to be very careful no Flux drips in either. Then vacuum, fill with nitrogen, vacuum, fill with refrigerant.

But you know that now, don't ya.

Sent from my SM-N910V using Tapatalk

 

[Porno Joe]

Ok apparently my damn vent thermometer broke.

I could not for the life of me drive that thing below 58.

So I grabbed an infared thermometer and hit the vent fins with it.

Truck running at 1750
Low- 37 psi
High- 280
Ambient temp- 77
Temp out vents- infared thermometer flashed 43.8 once but most times I was able to get 46 pretty consistently.

 

[Chevy1925]

There ya go

 

[bmc1025]

Perfect!

 

[Porno Joe]

ok bumping this back up.

I haven't used my AC since I worked on it two weeks ago. Today its 83 and humid here, so I decided to try it out. I'm pretty disappointed with it to say the least.

just doesn't seem my ac can cool my truck down enough. I have the digital climate control, I set at to 60 and recirculate, fan on max. I would say the cab was cool at best. I had no problem driving around for 25-30 minutes with the ac on max and it was not getting too cold in the truck. I tried knocking the fan down to see how low I could stand, had it on 2 and felt like it was getting warm to I bumped it up to halfway and it seemed like it would be tolerable there, but definitely not cold in the truck. my truck is a crew cab so not sure if that is impacting it?

Any ideas where I should look? I think my charge is pretty good. I do remember back in 2013 I think I had the pro ac shop recharge my ac system after I blew a line. even he said back then the ac didn't seem as cold as it should be.

Could there be something under the dash/in firewall I need to change?