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FTMFW
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139 Posts
Discussion Starter · #1 · (Edited)
Today I was on my way home from work and my air was blowing cold as usual. I heard a strange noise under the hood and it began blowing hot air. The belt is still intact and at idle when I turn the A/C on, the RPMs raise. I put a pressure gauge on the low side and it was reading 105 psi. Any ideas what has gone wrong? I don't know a whole lot about A/C but any help or ideas of what to check would be greatly appreciated.

BTW...the truck is a 1999 Sierra 4x4 5.3

TIA
 

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HOT AIR BALLOON OWNER
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14,932 Posts
LOL I would not just charge it with that much low side pressure!!! That is HUGE, like you have a block style.

Leave the system OFF and put some real gauges on it and see what is going on. The system should balance out when off.

Just do a search for me as a poster and A/C in the heading, you will read for hours.
 

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FTMFW
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139 Posts
Discussion Starter · #6 ·
It doesn't make any sense to me though. Why would there be so much pressure on the low side? Could my compressor going out cause that? I assume there is no leak due to the pressure...and I couldn't find one when I looked. When it originally happened, the noise it made sounded similar to a belt screeching and it was followed by an odd smell. It wasn't a freon smell...more like a burning smell. Any ideas?
 

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HOT AIR BALLOON OWNER
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14,932 Posts
It doesn't make any sense to me though. Why would there be so much pressure on the low side? Could my compressor going out cause that? I assume there is no leak due to the pressure...and I couldn't find one when I looked. When it originally happened, the noise it made sounded similar to a belt screeching and it was followed by an odd smell. It wasn't a freon smell...more like a burning smell. Any ideas?


Block in system creates excessive pressure on one side...

sounds like your compressor is dead/dying to me with what you said
 

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Iron Block LS2
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192 Posts
Sounds like the clutch froze up and wont engage anymore.

By the way....I hate this new R134 crap. I charged mine this summer and the freon isnt working anymore. Oh well, winter is right around the corner. I will deal with it next year.
 

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HOT AIR BALLOON OWNER
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14,932 Posts
Sounds like the clutch froze up and wont engage anymore.

By the way....I hate this new R134 crap. I charged mine this summer and the freon isnt working anymore. Oh well, winter is right around the corner. I will deal with it next year.


lol if you charged it and it will not cool, you have a leak or an overcharged situation. Neither of which is the fault of the refrigerant.

An original 134A system will cool well. Converted systems from R12 are usually crap unless the R12 capacity is very large to begin with... I mean well over 3lbs.
 

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Iron Block LS2
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192 Posts
Nope no leak. Its still under pressure.

I hooked up the gauges and released some of the pressure and when the freon is good, it will freeze around where you released it and turn to frost. It doesnt do that. Its just warm air coming out.

We have noticed that with alot of cars now a days. Its under pressure but the freon just turned to crap.
 

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HOT AIR BALLOON OWNER
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14,932 Posts
lol, refrigerant does not just "go bad" :rofl2:
 

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HOT AIR BALLOON OWNER
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Ok then why was it under full pressure but the freon isnt cold anymore? It was like that when I got the truck and this summer I charged it and it was cold.

I call bullshit on it not going bad.:crazy:


Uh, when you simply add refrigerant to an empty system there is still ATMOSPHERIC PRESSURE in the system... you know, the shit you breathe? The system has to be vacuumed down prior to charging.

In addition, if the system has BLOCKS it will read higher pressure than normal... same if you have failing cooling system.

Hell you could even have bad pressure switches.

How many systems have you rebuilt? Are you EPA certified? Did not think so.

I certainly do not know everything about mobile HVAC, but I seem to know more than anyone else on this site, you included.

PS - I have countless 12oz cans and 30lb tanks of R12 for my cars and this "old, bad refrigerant" still cools my cars fine.
 

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HOT AIR BALLOON OWNER
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14,932 Posts
Are you ASE HVAC certified?


Nope, I can barely keep up with myself and the rentals let alone time for that. The mechanical work I do is for my own enjoyment as a hobby, not a career. I would imagine I could pass it without a hitch if I had to do it.

Think of mobile HVAC like a transmission... you have steps to follow in order when rebuilding it, has to be SUPER clean, certain parts MUST be replaced, etc. Not too complex, but long and drawn out is the process.
 

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Registered
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159 Posts
+1 to Hit Man! HFC134a does not just go bad... Air does not turn to a liquid when pressurized... The liquid turning into a gas absorbs heat, that is why you say the "freon" turns to frost, what is really happening is the water vapor in the surrounding air is freezing.
 
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