The 04 Silverado has a slow leak.  I put one can of freon in it twice this cooling season so it would put out cold air instead of slightly cool air.  At no time did the freon get low enough to keep the compressor from starting...

I don't want to put this truck in the shop right now because our spare truck is on loan.   To make a long story short, is the freon with the "stop leak" worthwhile and will it screw up the equipment long term?

Not worth the chance of long term damage.

Get a UV dye can or a detector.


You can often find leaks by looking for the oil stain near them.

check the schrader valve. my ford truck had a slow leak at one time and the schrader valve had corrosion on it keeping it from sealing. a little soapy water or spit will show ya.

The cap on a Schrader is part of the system seal.

2nd this, if you still have problems locating the leak you can take it to a shop and have them use a sniffer

Thanks guys, I was afraid I was being a little too optimistic.

I didn't think about the UV dye until you mentioned so I picked up a can today.  Still need to find a light and the free time to give that a try.  The blower speed control started acting up over the past few days.  Yesterday it only worked on the high position and today nothing.  I swapped out the resistor today and it's still dead so I'll check the fuse and swap the resistor out again just in case I got a bad one.  Just my luck.  Damn it's hot.

order this light link

You can charge by temp and sat pressure just fine.

We used to have some temp-altitude chambers that used nasty refrigerants to get down to more than -100 C.

were not talking commercial refrigeration. superheat a cars ac? your fucking nuts. its a car. not a high efficient system.
charge it based on weight.

put in the correct weight of REFRIGERANT (not freon, freon is a brand name, typically used by homeowners that know nothing about it) and thats it.  if the tag is wore off, google it.  you will find an answer,  if its impossible (which it isnt) to find the answer, you can charge based off pressures and it will get you pretty damn close, but it depends on temp too and some conversion, and some math.

bring it to a repair shop. dont use the "AC pro" cans and shit.

Well, got the AC blowing again...  I couldn't find the wiring schematic for between the control switch and the resistor but this guy's video covered it very well if anyone else has the same series vehicle- Video .   After testing it was confirmed that the control switch was sending signal for the five speed settings but the resistor was failing at some speeds and the blower motor had failed 100%, no rotation.  Not bad for GM, the truck has about 125k on the odometer.

Still haven't had the time to chase the refrigerant leak but will report the results when ready.  

Thanks again.

Edit- BTW there is a service bulletin for the wiring harness it's -  #11046

Many GM trucks have evaporator issues of slow leaks. Sometimes can see some dye in the HVAC module, but not always. I run them till they are real cold, turn the system to the foot outlets blowing and slip a Freon detector probe up as far as they can go with it on a sensitive setting, they will start blipping. You can also go under the truck and go up the drain.

One other place to check it the bottom of the compressor pulley, the seals do leak.

Manufacturers no longer provide much of any data beyond using their proprietary charging systems.
And many of those operate solely on pressure.

It is not all that hard to look it up.

Car systems are not all that critical since they already have to deal with variable drive speeds.
That is why they have accumulators to try and buffer out variable loading and available RPMs.

No word from the OP for a couple of weeks.  Is AC the new safe thread?  



Forty two bucks?  Ouch!  I use this light and these glasses for about $19 total.




I've got a really nice digital JB gauge that reads down to 20 microns and it stays in my tool box for automotive work.  As long as the low side gauge goes down near -29" and stays there when I turn off the vacuum pump, it's GTG.

In terms of charging, it really helps to know how much by weight.  That number is usually on a sticker somewhere under the hood.  On GM look on the radiator cowl.  And unless it's some sort of jumbo system with separate front and rear evaporators, it will probably be less than 2 lbs - probably more like 1 1/2 lbs.  Either way, it's better to be under than over - undercharge means that the accumulator runs low.  Overcharge and your evaporator pressure is too high and doesn't get cold.

This is the chart that I use -



Consider the high side pressures maximums and you should be ok.  Squirt in 1 lb, then watch the high side pressure as you add more S-L-O-W-L-Y, waiting several minutes in between to let the system equalize.  If the low side pressure starts climbing - stop, you've gone too far and it won't cool.  And don't forget to put a fan in front of the radiator or else the high side pressure will go crazy.

The light I linked to is the one I sell. I know it is a quality light. In my experience, the multiple led lights have been junk. A bunch of LEDs that are very dim.

I'm not dead yet!

Hope to get back to this soon...  Work has been kicking my butt and thank you for the chart.