'97 Tahoe Air Conditioning question

[jeffjcalweb]

Hi - I am most certainly not a "shade tree" mechanic by any stretch, just want to get that out there... so I did watch several videos for recharing A/C unit as mine is just blowing hellfire.

I hooked up first can w/the digital gauge and it read 0 psi so clearly not good lol. I followed directions and started adding, stopping every 15-20 seconds to check. The PSI would increase but immediately start falling - so to captain obvious of course there's a leak!

Now, when I finished adding a can (might as well I was already in it by this point) and turned the engine off, disconnected the hose from the can to the service port ... I could hear a "hiss" - again captain obvious nods his head saying "yep there's a leak!" ... it is the valve next to the charge valve. if i remove the cap off the "high valve" the hiss stops. So does this mean the leak is at that high valve (sorry I don't know the actual part name)? When I put that cap back on the "high valve" - not even tightening it, literally just placing it on the valve ... "HISSSSSSSS" ...

So I'm willing to take a shot at fixing this before running back to mechanic. I just don't know what the next step is...and can I do something as stupid as buying another can, trying to charge again, but leaving that cap off the "high valve"?

Thank you to everyone who is smirking, smiling, shaking their head and taking the time to give some advice!

 

[jeffjcalweb]

Ok well some google reading already has explained my super savy "high valve" wording and that is the expansion valve and maybe it is doing its job and therefore my leak is actually elsewhere...meh.

 

[drakon543]

so throughout your reading did it happen to mention if the system is completely empty a diy charge can wont work? generally when the hvac system is completely empty it needs to be purged and have a vacuum charge (-charge) to properly accept any charge? there are check valves and such in your system that are only operated through vacuum and positive pressure. if the a/c system wont cycle itself it wont pop these valves to allow the system to be charged correctly. also your hissing sound is probably only audible when the caps in place for the escaping pressure to hit something.

 

[jeffjcalweb]

Well .. no lol. But now I know. So much for simple fix! Thank you!

 

[exp500]

However- you figured out how to add some.....So, Add some fluorescent dye and one can of R whatever and try to run compressor some so you can find your leak. Or figure out a way to put air in and look for leak(s). Bubbles good for big leaks.
Still need to evacuate system before charging.

 

[OR VietVet]

If you do open the system at all, change the accumulator and orifice/expansion and flush the system out. That hiss you heard was the shrader valve allowing pressure past it till the hose is completely removed and the valve gets a chance to close itself and shut off the leak. The easiest way to START looking for leaks is to look at any connection points and look to see if there is oily dirt there. The refrigerant oil comes out of the system with the freon leak and mixes with dirt to leave that residue buildup. Next would be any swollen hoses. All systems with enough age will eventually leak because of temp extremes under the hood and the constant vibes while driving.

 

[exp500]

PNWVietVet- I wish the service manuals were easier to come by. The Newbies could save themselves alot of trouble by just reading thru once on whichever issue on the list.

 

[OR VietVet]

For gobs of years there have been the basics of starting to diagnose an a/c problem. If you have no gauges and at least a minimal idea of how a/c works and what to look for initially, it is best left to a pro or if the rig owner doesn't mind, they can just dig in and destroy the a/c system LEARNING what makes it tick.

Every now and then you can see actual shop manuals for sale at the "parts" section of a site. I see them on CL all the time. The next best way is the ALLDATAdiy.com site.

 

[jeffjcalweb]

Well hey I learned stuff today so that's a win! Thank you for the help. I did confirm a leak. I rented a vacuum pump and found an exact walk through on Youtube ... When the pump is running it can get to about -25 and that's as far as it can go. The second I turn the pump off, bam right back to 0psi. Like instantly. Going to assume that means "leak". I'm not upset though because today I learned something and tried something in 50 years I never even gave a thought to!