AC not blowing cold but Gauge pegs into red area indicating there's freeon in sys.

[Sprung Monkey]

05 Chevy Express 3500.
AC not blowing cold but Gauge pegs into red area indicating there's freeon in sys.
my AC was working fine 2 summers ago last year not so much an now it's worst.blowing barley cool.
I connected the el cheapo single gauge started engine gauge moved to the red, then compressor kicked on gauge went to lwhite for low then back to red.

I stopped bc I didn't want to over charge. or is my sys. way undercharged an I should continue charging?
please advise an thanks

 

[Mooseman]

You need a two gauge setup. The low side will show higher pressure when the compressor is off and then drops. To me, that looks like it's under charged or there is a severe blockage preventing the flow of gas. Maybe the orifice tube is plugged. At idle, it should be running steady and not letting the pressure drop so much that the low pressure switch kicks off. To really know how much refrigerant you should put in, you should have it evacuated and refill with the amount by weight as per the manual or sticker under the hood. And before that, you should check for leaks.

 

[Sprung Monkey]

I think your correct on being low on freeon. since it's low maybe I should crack open the sys. an let out whats in there then remove an inspect the orofice?

at idel I do hear an see the compressor kick on just for a sec. then back off is this why you suspect the blocked up orofice tube.

what I am concerned w/ is overcharging an having the sys. explode in my face.

when i rebuild the whole sys. (so I know what the orofice filter is)on my car I had the 2gauge an rented the evac pump. mite be time to get another 2gauge set. you know I paid $30. for the single gauge at autozone an the inexpensive 2gauge is the same price. thanks Mooseman

 

[TJBaker57]

FWIW, those that have an OBD2 adapter and an app that reads live data PIDs.... You may be able to read the high side pressure with a custom PID entry. It very likely will not be included with the app but creating a custom PID entry can often be added.

I know my TrailBlazer 4.2 PCM broadcasts this data near continuously.

 

[Sprung Monkey]

this switch has been known to leak
GM Genuine Parts 15-5715 (01132749) Air Conditioning Cycling Switch

since there's not much freeon maybe half a 12oz can maybe I can get away w/ loosen a service valve to empty the remaining freeon then swap these service valves?

this low preasure valve has been known to leak.

this high preasure valve has been known to leak

high preasure plug.

and orofic filter

then rent the vacum an buy some decent dual gauges? add some freeon w/ the dye to check for leaks. I probaly should pump in shop air w/ dye.but would prefer to just bolt on a few known to fail parts an hope thats the only leak.

 

[Sprung Monkey]

FWIW, those that have an OBD2 adapter and an app that reads live data PIDs.... You may be able to read the high side pressure with a custom PID entry. It very likely will not be included with the app but creating a custom PID entry can often be added.

I know my TrailBlazer 4.2 PCM broadcasts this data near continuously.

I'd should have this OBD2 scanner an related probaly torque pro app. just haven't pulled the trigger on it yet. now I do have this scanner an I believe it reads live data.

https://www.amazon.com/dp/B07Z3HB7DR/?tag=gmtnation-20

thanks

TJBaker57​

 

[Mooseman]

To know where you are losing refrigerant, you could get yourself a leak detector before you open up the system and start throwing parts at it.

Amazon.com : refrigerant leak detector

Doesn't have to be expensive. I've had one from HF for years and has been very useful in finding leaks for me.

https://www.harborfreight.com/electronic-freon-and-halogen-leak-detector-92514.html

Since it still has some gas left, it may be just a small leak but better to check.

I doubt that scanner could show A/C sensor data. Looks pretty basic. Best would be a dongle like this one and @TJBaker57 could show you how to add the PIDs on your Android phone or tablet to get that data. A much more useful tool.

https://www.amazon.com/dp/B011NSX27A/?tag=gmtnation-20

 

[Sprung Monkey]

thats good to know a freeon leak detector is inexpensive. this seams to have good reviews.

https://www.amazon.com/dp/B0CCV7JZBH/?tag=gmtnation-20

what do you think of this one?
thanks Mooseman

 

[Mooseman]

Looks alright. The UV light can be useful to find leaks as well if there is UV dye in the system.

 

[Sprung Monkey]

I purchased the proper gauge set and the sniffer. I intend on getting the AC UV dye add a couple drops into the gauges yellow tube add a bit of freeon. then get out the sniffer an flashlight.
now my AC compressors clutch does engauge just how much freeon should I let be sucked in just for the leakdown test?

 

[Mooseman]

If it already has some in the system, you don't need to add any. If it's empty, one can should do for a leak test.

 

[Sprung Monkey]

OK gonna connect the gauges up soon. how many drops of the UV dye to pour into the yellow gauge tube? thanks Mooseman

 

[Mooseman]

It should have come with instructions. I don't think it needs a lot. To work, it would need to circulate around the system. And it won't make its way into the system unless you add some refrigerant using the gauges.

 

[movietvet]

I think you can buy refrigerant that has the dye in it already.

 

[Sprung Monkey]

AC diagnosis` I already know she blows coolish/warmish air
1.verify the compressor engages I believe it does.
2.connect gauges test red an blue pressures I'm anticipating very low if any pressure. if yes goto 3. NOTE always keep red valve closed! only open blue valve.
3.add a couple drops of AC UV dye into yellow gauge tube then connect my shop air to the yellow tube add 60PSI an search w/ UV flashlight /listen for leaks an see leaks w/ soapy water bubbling.at all connection points.

after replacing leaky parts like the shrader valve this part
an swap in new oroface filter
vacuum the sys.turn blue valve counter clockwise red always stays shut.vacumn for half hour. an observe if sys. holds vacumn if she holds for half hour then leaks have been repaired an shes ready to
recharge w/ freeon.
1.close blue valve
2.connect freeon can to yellow. turn can piecer clockwise to open can then counter clockwise to release freeon, w/ can held upright at 12 o/clock purge air from yellow tube. open blue counter clockwise just a little then more gradually freeon now entering sys. observe freeon entering sys. though peep hole. wait till can feels empty. close blue valve replace new freeon can an fill more freeon. 2 an a half 12oz cans. will confirm oz on the lable in engine area.
3.after recharge test all connection points w/ sniffer. at dryer,firewall, pressure ports, at compressor, at condenser. dune.
unsure of when to add the 100 pag oil an how much? an if I have the correct type pag oil
? thanks for advise

 

[Mooseman]

I don't think adding UV dye with shop air will allow it to circulate and leak out where there is a leak. If using shop air, I would check different places with soapy water in a squirt bottle. I wouldn't use it inside the Shrader valves though just to be sure to not get it inside the system when refilling.

When doing your final fill after vacuuming the system, I usually purge the line of air after I connect the can and before opening the blue valve. I open the valve on the can piercer and slightly unscrew the yellow hose at the gauges or use the purge valve if there is one. Just need a little pffft to get the air out, not as much as what is in this video.

 

[Sprung Monkey]

update:I think your where correct on your initial evaluation low on freeon.
I connected both red an blue then opened just the blue a tiny bit both gauges moved a little.

then opened the red a little when I opened these valves I heard a leak searched around only to find she was leaking from the dam yellow tube. I accidentally had the can priecer open w/ no can attached.

so I closed the can pricer no more leak to be heard. so far the gauges haven't moved in 40 minutes all this w/ engine turned off.

could I have introduced air into the sys. where I have to vacuum? or can I start recharging?
I plan to dump the whole tiny can I think it's a 1/4oz of UV dye into yellow tube
however when I purge the yellow tube won't it blow out all the dye?

or should I pour the dye into the red or blue tube?

but since my oil can attaches to the yellow tube (screws on same as the freeon can)still unsure of how to regulate the amount of oil?

the GM lable says .81LB front only 1.41LB front an rear. but neglectes to mention the type of pag oil.

this van is actuely a RV van I'll have to find out if she has a rear AC.when she was built it came w/ a roof mounted RV type AC, I believe there's no rear GM AC.


when I rebuilt the whole AC sys. on the car I purchased this Pag100 oil then found out car uses pag 150 (IIRC) so I didn't add any oil bc new compressor was full of oil I actuelly had to dump half the compressor oil out.

delphi lable next to GM AC lable
thanks for advise

 

[Sprung Monkey]

will try out the sniffer not sure if the engine should be running w/ AC turned on to use the leak detector?

new plan
will take a peek at the evaporator core behind this cover I can remove a what appears to be a 24 pin electrical connector and peak in.


.if theres tree leaves block the core I'll clean out.
w/ this low of freeon an a cleaned evapartor core will she cool a bit? if yes then recharge an expect normale cooling?
if evapoator core is clean.
then evacuate the freon replace oroface filter then recharge. will report back
edit: this man is very knowlegdeable

I believe the false readings his sniffer where detecting was due to the sniffer tip being to close to the tubing I believe th e sniffers tip must be 1/4" off the tube not in direct contact w/ tube.

 

[Mooseman]

I would vacuum it, check to see if it holds vacuum and then fill it. You have so little in there now that the sniffer may not pick it up with so little pressure. Once refilled, I would then go with the sniffer.

Good idea on cleaning out the evaporator

 

[Sprung Monkey]

update on my progress: I used the freeon sniffer at an around all the AC tubing consentrating on the dryer connections an preasure valve also the top condenser connection an slowely on front of condenser result no leaks detected.
I was suspious of leaves an pine needles somehow entering the blower case where the evaporator core is housed. that housing is packed w/ leaves an pineneedles.
I extracted a little bit w/ needle nose pliers will completely remove this houseing an thoughtly clean.
will my house hold preasure cleaner be to powerfull to blast the leaves that turn to mud inside the cooling fins?
I'm assuming the leaves where obstructing airflow basicely choking off the compressors air supply.
will report back later.

 

[Mooseman]

It is a camper so it's been in the woods

There should be a screen at the cowl that prevents stuff like this from getting in. May be broken or missing.