Ac not working . Need help to identify issue
 

Well here go again .
The Ac decided to stop working now in Summer with temperatures rising the 90 this is a killer

Will appreciate if anyone van help to identify the problem

Compressor is not clicking. There was a slight smell after it stopped
Working.
I test preassure with gauges shows 0 but seems normal since the compressor is not working
Is there a way to bypass the preasure switch
Or directly power the compressor
Any help appreciate

if the smell was a bit electrical coming from the compressor it might have burned out the A/C clutch. you can check it for resistance to see if the coil is still good you can also check to see if it is receiving power. if it is receiving power then again check the clutch for bad wiring or ground or failure.
if the smell was freon then the compressor might have blown a front seal or o-ring in that case look for dye or oil stains.

Had a similar experience 2 years ago, the smell was burning rubber caused by the compressor seizing and the belt slipping on the clutch pulley.

When the Snowflake symbol "ON", the compressor's electrical clutch engages, pressure builds-up and the pressure switch operates, so bypassing the switch won't make the compressor work.

There's a connector mounted on the compressor (accessed from below) which connects the electro-magnetic clutch, if you press the Snowflake button with the engine running you might hear it "click-in"

If there is no pressure with the compressor is running i.e. the clutch has engaged, then there must be a massive leak somewhere.

I think my compressor failure was caused by my local aircon service shop overfilling, Hummers only require 1.6lbs of R134a refrigerant, overfilling puts too much strain on the system. I eneded up replacing everything except the heat exchanger which I flushed out, there was metal debris everywhere!

I've attached some useful diagnostic info on the subject.

Hope you get things sorted.

If there is no pressure then you have a leak, even with the compressor off there is pressure in the system

Depending on ambient temperature the pressure will be over 80 psi it 80* F or above if the correct amount of refrigerant is still in the system.

Neal

You'll need to locate the leak and repair it, look for a large spot of oil, when the refrigerant leaks it also carries oil with it.

Neal

Thank you all for the replays

I did a vacuum test today and it didn't hold the vacuum. There was not freon on the line

The leak must be kind of big since the vacuum didn't holdi for more than 30 sec
At this point im not sure if the compressor went bad since the clutch wont engage due the lack of preassure

Only oil I see is in between the high and low valves there is a connection and all the line is dirty . Hopefully that would be the issue and not the Evap

I think I will replace the compressor as well , not sure if it is. Worth it to fix the leak put freon to then find out the compressor is bad

For now I will rent a car WITH AC. :)
I wont be able to touch it till July
Will keep posted

Thanks

legerwn's advice is good, also you can add UV dye to help find the source of the leak if you can get it without vacuum. Indeed I found the HI and LO pressures sat around 80psi even though the compressor was broken.

Many posts refer to the refrigerant as "Freon" I think this CFC has been banned and replaced by r134a

Few other things:-

• There are many O-Ring seals in the system, most of mine showed signs of age and contamination, I would replace them all as you can by a bag of these very cheaply.
• The LO and HI schrader valves are apparently very common issues, these are cheap and quick and easy to replace.
• The condensor sitting on the front of the radiator is also prone to damage, in fact my new replacement was faulty from the start.

If I could have I would have got a garage to do mine but here in the UK no one would touch a Hummer. The hardest bit was the bottom condensor pipe which took a lot of time and patience.

Just to add there are a lot of useful youtube videos on the subject, well worth watching.

Oceanbrave ... Now you mentioned . I would check the front condensor since I was working on the radiator I may have damage it .
This not going to be fun with 90° plus outside
Wish I had a garage

If you see any oil at that union between the high and low fittings, that is where the orifice tube goes. It is possible that the orifice tube got clogged or jammed up which can cause a failure and enough pressure buildup that the o-ring at that joint blows out. The tube is cheap and easy to replace. I'd look close all over the condenser and all lines though as mentioned to see if you see any sort of oil where it might have leaked out. Of course it could very well be that the compressor or compressor clutch just died.

If the compressor grenaded and/or you see a bunch of debris on the orifice tube screen than you probably need to get the entire system professionally flushed out and gone over. You dont want to suck debris into a new compressor and blow it up too.

Its not too expensive to replace, just a bit tricky to access.

As mentioned the hardest part was accessing the lower condenser connector, to do this I removed the short bumper (RHS) and used a socket wrench and then my hand to spin the nut-off.

Also had disconnect the hood's cable restraints, support the hood and remove the cross-member that runs over the top of the radiator, even had to remove the two horns!

The replacement I baought was poor quality and leaked so I ended-up flushing out the old one and putting it back. So I effectively did the job twice, wished I'd bought an ACDelco!

Hope you fix it!

https://cimg1.ibsrv.net/gimg/www.hum...41e3c9281d.jpg
Orifice Tube
https://cimg4.ibsrv.net/gimg/www.hum...37181bdd1c.jpg
Pipes and Heat Exchanger
MixManSC has a very important point about "debris"

My compressor had indeed "grenaded" and there was a ton of debris everywhere! (see pics)

Using a flush-gun kit + fluid (search youtube) I flushed out the heat-exchanger and every remaining pipe, as the dryer, orifice tube and compressor were replaced these didn't need attention.

Some experts do not recommend flushing and advise compoenet replacement, but that can be expensive and impractical. I kept agitating and flushing in both directions until no more debris came out and then continued flushing a few more times just to make sure.

.. The orifices tube looks exactly like yours debris everywhere
Check pics

I will look online and perform a flush

Is it necessary to flush after the tube . I think this act like a filter
In other words . If Im replacing the dryer and compressor. What would need a flush
https://cimg1.ibsrv.net/gimg/www.hum...395277058d.jpg

That's remarkably similar!

If you're replacing the compressor, with all the cost and effort that involves, I'd be tempted to reverse flush and forward flush the A/C Evaporator, all the pipes and its generally recommended to replace the condensor.

The theory is that small particles of debris get lodged in the micro cavities of the condensor which are difficult to flush out. Having said that, I had to flush mine as the new one leaked and it would have taken too long to get a replacement shipped to the UK.

Also there is the residual oil inside the old components which makes calculating the required amount of PAG Oil difficult, flushing helps remove it. I've attached an official GM service note and anoth Tech Tip which you may find useful.

Thank you .. those link are helpful.
Will get into it in a couple weeks . Will post after

https://cimg8.ibsrv.net/gimg/www.hum...43caf2a682.jpg

https://cimg6.ibsrv.net/gimg/www.hum...c21291b03c.jpg
Hopefully you'll get your A/C running 100% and it would be good to know your progress :-)

It was July 2017 almost two years ago when I did mine, my A/C Temperature ran higher than ambient, when I started it measured 24C(75F) after it hit -3C(27F) an amazing improvement!

Cooling has dropped off a bit since as r134a molecules are small and tend to escape even perfectly sealed systems, so its no surprise, however its still effective.

Some UK Hummer owners don't bother if their A/C don't work, but they miss the point, if the HVAC system can't cool it can't regulate and the cabin temp drifts all over the place.

Again Good Luck!