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2003 Sierra AC Blowing Hot Air
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Putz
New User
Jun 28, 2008, 9:54 AM
Post #1 of 6
(2290 views)
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2003 Sierra AC Blowing Hot Air
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My 2003 Sierra 2500 just started blowing hot air after working just fine for the past four years. With the AC on full the compressor clutch is not engaged. I checked the fuses and they are still OK. I went to the local Auto Parts store and purchased an R134 recharge kit in an attempt to remedy the problem. Once I attach the kit to the Low side service port the gague that came with the kit immediate spikes to the maximum it can go and no coolant flows into the system. I'm assuming the system is fully charged. What might my next step be?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 28, 2008, 11:25 AM
Post #2 of 6
(2286 views)
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Re: 2003 Sierra AC Blowing Hot Air
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WARNING! That kit won't charge with compressor not engaged and probably has other than refrigerant in it to help you spend about 3 grand to fix the thing!!
The static pressure of the system would read off the silly color gauges as those if and when they rarely are accurate are only for when compressor is running.
With all fuses known good the next step is to look for the low pressure cut out switch on low side hose or accumulator and if two wires only go to that switch we can proceed.
Read the container you have. If there's any sealer, O ring lube, oil (type not disclosed) it's the equivalent of "fix-a-flat" for a tire ---- DON'T USE IT!
Note: Refrigerant static pressure is like checking tire pressure. Refrigerants have this neat characteristic that makes the pressure noted just sitting there about what the temp is in Fahrenheit! Whether there's just a few ounces in system or a pound too full - same reading. It's NOT like air!
I'll make a wild guess right now all you need is a new low pressure cut out switch "LPCO" and we can test for that quick and easy. Look for it and report how many wires go to it. It can be replaced by hand and not involving the charge in the system at all!
T
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Putz
New User
Jun 28, 2008, 12:21 PM
Post #3 of 6
(2280 views)
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Re: 2003 Sierra AC Blowing Hot Air
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Thanks. There are two wires coming out of what I suspect is the LPCO on the accumlator.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 28, 2008, 1:00 PM
Post #4 of 6
(2278 views)
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Re: 2003 Sierra AC Blowing Hot Air
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Make sure that's the one. Again - it's on the low side (larger plumbing) of the system and should look sort of like a spark plug with connector and the TWO wires.
Now with A/C known requested and any button lit if this uses the A/C enable button when that plug is unplugged one side will show voltage - check with a simple test light/circuit tester. If it lights up great!
Interim note: That switch is merely but importantly an on off switch to enable compressor's clutch if and only if there's adequate pressure in the system. When it's freezing cold out system pressure would be too low, or if the A/C has cooled you as much as it's limits allow it will cut out compressor to prevent liquid refrigerant to return to compressor and choke it. It will also cut out when system is generally way too low and no pressure present.
You already said your (death kit) ((that's what those are called in the trade)) spiked up pressure of some unknown # which was at least an indicator that there's enough refrgerant in the system that it should be attempting to operate.
Back now. The switch has power to one side (ignore this and report if it doesn't) and it probably isn't getting to the other but we don't know that yet. Either way - test with it plugged in if you can probe the output side/wire if it lights up - sometimes hard to get at. Other is to take a paperclip and jump the two together and clutch on compressor should engage. If so, then see if it's now blowing cold air for you inside. DO NOT LEAVE THAT JUMPER IN PLACE AND DON'T LET THE CLIP/WIRE TOUCH ANYTHING GROUNDED! Checked by thermometer helps with all this checking. If all is just fine then replace that switch. It should just unscrew without leaking refrigerant but at one point will spit as it has an O ring and depressed a shrader valve much like a tire has. If hissing continues it might not use a shrader as a check valve and all refrigerant would be lost and you could be freeze burned by escaping refrgerant - STOP IF ANYTHING DOESN'T BEHAVE AS I JUST SAID and hit back.
If determined earlier that this is the switch and worried about removing it and loss of refrigerant go get the new one and look to see if inside has a new O ring and a small bump/pin - something that would depress the shrader pin when it's back on snug.
Use a good glove when removing if you get to that. It may or may not have a hex for a wrench to get it started but many will go by hand alone. Now ( I'm certified nuts as the web already knows) go in house and find some baby oil to lube the new O ring! No kidding it's a good lube for A/C parts! Just a smear. If none of that around a smear of silicone or dielectic grease (just a smear) will do fine too. If it's wet from removing the old one that will do also. Tighten back on firmly but don't go nuts. About the force a screwdriver would do if it was just a screw. Check and be ready with some soapy water to look for bubbles there - tighten just a tad more if any seen. If it breaks or anything goes wrong in installation take it off at once.
Again: If any doubt or questions stop and ask. This should be that easy. Disclaimer: Like any advice on this and most sites it's AYOR.
Hope this helps and is the only trouble and if all works as I should it's done. Good luck. This is a pretty common problem with GMs in particular for some reason and failure of new parts is up there too. If it worked with the paper clip jump it should at least partly work when a good switch is in there,
T
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Putz
New User
Jun 28, 2008, 5:07 PM
Post #5 of 6
(2273 views)
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Re: 2003 Sierra AC Blowing Hot Air
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 Wahoo!!! That was it on the nose. Not very hard to do at all and not muck coolant leakage either. The AC is working just fine now. Thanks for all of your help.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 28, 2008, 5:24 PM
Post #6 of 6
(2271 views)
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Re: 2003 Sierra AC Blowing Hot Air
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Cool man! It's really my Kitty that knows what the heck she's doing - I just type!
Kitty accepts Iams gift certificates or Fancy Feast Turkey - Grilled and sliced please!
Glad it worked out. Something just flew out of my puter and said that was it.
NOTE: Had you jamed junk from a death kit in this it could have flicked up the whole system. There should be warnings on those things that even the attempt could cost thousands! No Joke!
T
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