Automotive Air Conditioning Information Forum (Archives)
What are they teaching in the Tech Schools?
GM Tech on 
Thu September 09, 2010 10:41 PM 
Got a call from a guy who was referred to me today...says he can't find the high side scrader valve for a '94 Caprice. I said I have some, but why do you need it? He says the supervisor at the local Tech school told him he needed one- because his sniffer goes off when he sniffs at it. I say- ok back up-- why is your cari in at a Tech school- what is original concern? He says- it was dead flat- no refrigerant- they charged it up, now it leaks from the valve, and needs a new one...I said - WTF - that is how I test my sniffer- meerly sniff a port with no cap on it---then put the cap on it and sniff again-- with cap on- no problem- it seals like it should. He tells me the car has no cap on it now-- they forgot to put it back on- or they lost it.....Now I know where all the Dealerships Techs get the idea the cap is not important- Heck they teach it right in the Automotive Tech schools
So I ask- their conclusion is the valve is the entire problem? He says - yes... I tell him he will be dead flat in another 2 weeks or two days, or two months...He'd better get another look at it, because a good cap with a good rubber seal in it will seal off any type of leaky schrader- that's what they are on there for.....Common sense says to look closly at the shaft seal and belly o-rings-- but those are down low on the car- the cap was high up-- a whole lot easier to blame- don't have to put the car on a lift.... oh and B-cars are also famous for the suction hose rub-thru on the upper A-arm....better look there too!
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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
NickD on Fri September 10, 2010 5:00 AM
Don't get me started on schools, yet another governmental type of organization, tech school in my town robs me each year for a good hunk of money on my property tax bill. If I had a prerequisite for tech school instructors, it would be they would have to prove they can make a living in the trades they teach, for at least five years, most are a bunch of idiots that wouldn't last five minutes with a real job. BS their way for three years, then get on tenure and have a job for life with early retirement and full health benefits.
A Scharder valve in a 1994 Chevrolet Caprice? Thought this was R-134a, just a handful of GM SUV's got an extension to use R-12. Most Scharder valves I have tested seal darn good, if they don't, very easy to replace, even have a tool for those where you can change one without discharging a system. R-134a ports definitely need a cap, what idiot came up with this quick coupler design,all quick couplers leak. Scharder valves are tapered for a good seal, just use a flat disk on R-134a and can wiggle and wobble and its seating is not repeatable, and since it already has a groove in it, you have a leak. All at a time when yet another governmental organization is screaming about leaks.
Caps use to be metal, plastic caps are crap, least I still can buy metal caps for my tire valves. Especially on the high side where it gets extra hot, plastic get brittle, try and tighten it with your baby finger, and end up with a bunch of broken pieces of plastic in your hand. Are these EPA approved? Is all this for real? Or is there someone with a candid camera filming all this for a comedy show? It's a big f__king joke, least I hope it is.
GM Tech on Fri September 10, 2010 9:20 AM
I used the term schrader valve to describe the new 134a style ball valve---I haven't heard a common name for this valve yet.....it is the same valve that is on almost all GM vehicles with 134a......
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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
NickD on Fri September 10, 2010 9:36 AM
Well if it is one of those, sure needs a cap, even one with a bit of rubber on the inside. Something else to check to see if there is anything left of that rubber disk jammed up on the inside.
SpinRite on Sat September 11, 2010 1:01 AM
Them as can, DO!
Them as can't, TEACH...
Edited: Sat September 11, 2010 at 1:02 AM by SpinRite
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