A/C trouble shooting question

[Keats]

  5 Apr 18

2000 Chevy Silverado 1500 2 wheel drive, Ext cab, LM7 (5.3 ltr ), Automatic, Vin "T", 86K miles.

 

My truck has been parked outside in the Arizona heat for about a year. During that time I've probably put a few hundred miles on it. It's our 3rd vehicle and seldom used.

I took it to the lumber yard last week and the drivers door window would not operate. Needless to say, I had to replace the regulator. Works perfect now. So because the window was in the up position, I turned on the A/C.

Nothing happened except lots of hot air blew into the cab. It was working just a couple weeks previous. It made no sounds, or showed any symptoms of not functioning as it should at that time.

 

So I've been researching possible causes and determined that the Compressor Clutch was not engaging at all. I swapped the relays in the under hood fuse box and still nothing. Today I tried a jumper across #87 and #30 in the relay socket and the clutch clicked on and then off as I removed the jumper. So it's not a Compressor Clutch problem. There was no feeling of cold in the A/C under hood line to the condenser and no feeling of heat on the other A/C line running from the condenser. Had the compressor been functioning, they would feel cold and hot to the touch depending on which line you were touching.

I do not have a set of A/C gauges to check the refrigerant pressures, so I don't know if the refrigerant is low (or gone) because of a leak?? I checked all of the fuses that might have anything to do with the A/C system working and all are fine.

 

So I'm open to any suggestions that any of you may have for me. Is there another type of test I can perform to see what might be wrong. ?

 

I always do my own automotive work. I do not want to take it to a shop unless I have a very good idea of what the cause of this problem is.

 

I sure don't need some guy telling me I need to tighten the A/C "Kanutin Valve" or change my "Directional Fluid" if you know what I mean.

All replies will be appreciated..

 

Keats

Phoenix

 

 

[sefiroxx]

Did you check the lines with the clutch engaged? If yes, then you have a leak as the system would not engage the clutch under low pressure scenario.

If not, try again with clutch engaged. If the lines are cold/hot, then likely a failed pressure sensor.

Bbuuttt, you'll need a set of guages to accurately diagnose.

[Keats]

Tried that. No difference in temp on either line. I know the Discharge hose (rubber exterior) should be cold to the touch. The bare aluminum thin line should be hot. They are the same.

[O_J_Simpson]

If you do your own auto work why not buy a set of A/C gauges and you will not nave to guess any longer?

[Keats]

Good point. I'm looking at Craig's today. Thanks..

[Keats]

So, knowing that jumping the relay socket will cause the clutch to engage, it still will not run.   My thought now is that the refrigerant level is too low to allow it to function. I don't want to add refrigerant to a possibly leaking system. If I were to disconnect the low pressure switch at the accumulator and jump the wires that lead up to it, is it possible to have the A/C compressor function? Without it running, there is no way to get a true pressure reading that I know of.

Naturally I don't want to cause any additional problems and I'm not sure if jumping the low pressure switch wires would do that.

I'm open to suggestions...

Thanks,

Keats

Arizona

[sefiroxx]

A properly filled system will have a resting (static) pressure in 70-100 range (depending on temperature). Initial guage hookup will tell you of the system is full, low or out.

[silveradosid]

walmart and buy one of those charge kits screw the can on and hook to low side fitting and it will show you if you are low or if you have zero pressure then you have a leak

[Keats]

Sorry for not getting back to this posting. Out of town for a while. I was not award that there would be a static pressure if the system was not running. Will consider a set of gauges and see if I have any pressure at all.

Then maybe a leak test and repair if needed and a refill if needed.

Thanks...

Keats

Arizona.

 

[Keats]

Finally got everything working like it should.

I would up taking my truck to a guy near me that advertised on Craigslist. He offered to check the system, look for leaks, and evacuate the system and refill it to the proper amount of refrigerant for $75.00.

He works out of his home garage after his day job as a diesel mechanic. When he hooked up the gauges, it read very low pressure in the system. He added some nitrogen to the system to test it under pressure. No visible leaks noted. When he removed the gauge from the high pressure fitting, it would not seal and all of the nitrogen blew out of the now open valve.

I went to the local part store and bought a new high pressure fitting and returned to his home. He replaced the fitting and checked it again. Everything worked very well. His opinion was that this fitting was the cause of the leak over the years.

He also installed a new schrader (sp) valve into the low pressure fitting.

Then he swapped out the gauges and vacuumed the system to a -30PSI. When it got there, he let it stand for a good while to see if it changed at all. It was rock steady and he then set his machine for a total of 2 lbs of R134a refrigerant and I started up the engine. While holding it at about 1200 rpm for about 10 minutes, it eventually accepted all of the required refrigerant. My thermometer placed in the dash vent kept going down till it finally read about 48 degrees.

Being in the Phoenix area, that's a good temperature to achieve.

All of this took less than 2 hours, including the run to the parts store. O'Reillys charged about $12.00 for the fitting and new schrader valves and I later saw the fitting at Rock auto for less than $2.00 so that sucked, but such is life I suppose.

Now the truck is blowing good cold air and hopefully I'll get another 17 plus years out of it. :-)

After seeing all of the things that the mechanic did, I know that I could have done the repair but it would have caused me a lot more time and a lot of reading the service manuals just to figure out what he knew by experience. So the $75.00 spent probably saved me more $$ in the long run. Gauge set, valve, refrigerant. It all adds up.

Thanks to everyone for the great tips.

Keats

Arizona.

[Dnt]

Great followup. $75.00 is a tank of fuel nowadays so great price too.  Lots of times the service ports do leak plus all vehicles HAVE to utilize flexible lines and refrigerant slowly leaks out of any flex lines so after 18 years it would most likely be slightly low anyway.