New From Vermont, 2004 GMC Sierra Owner

Discussion in 'Introductions' started by JungleRamen, Jul 21, 2015.

  1. JungleRamen

    JungleRamen Member

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    Hi, new here from central VT.
    I own a 2004 GMC Sierra SLE extended cab with the 5.3L.
    I like to do what work I can myself, and I was a Mechanic in the Army from 02'-05'.
    Anyhow, just introducing myself.
    Figure this will be a helpful resource for my DIY projects and general advice if I run into problems.
    My AC just died the other day. I don't know much about how AC works, so here I am.
    I've owned my truck since last may of last year, and got it with 92k miles on it. It now has 100k.
     
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  2. jkeaton

    jkeaton Full Member

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    #2 jkeaton, Jul 21, 2015
    Last edited: Jul 22, 2015
    Welcome to the forum. As far as your ac system, it could be low on refrigerant or the compressor took a dump. Check the fuses, jump the low pressure switch momentarily to see if the compressor runs. If it does, it's probably low on refrigerant. You could refill it with a kit from Walmart, but if you have a leak, it will just leak out again. In that case, you gotta find the leak and repair/replace whatever is leaking. Might be easier to just take it somewhere and have it properly diagnosed if you are not familiar with those systems.
     
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  3. Bad88

    Bad88 Full Member

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    Welcome to the forum. Hooah (HUAA).
     
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  4. MrMarty51

    MrMarty51 Full Member

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    Welcome to the forum Jungle.
    First, check the fuses; :idea: read all the way through this before proceeding, not guaranteed that, I have it all in order, should be close though. :rofl:

    Buy a set of AC gauges, comes in a kit, manifold, hoses and gauges. Hook it up, check the static pressures, should be about 120 to 130, if it is lower, the compressor should run but, will kick in and out constantly, if lower than about 90 then, hook up and install a can, constantly shaking, held almost horizontally, see if the compressor will then run, fi not then, follow through the rest of the steps.
    Check any fuses relating to the heat/AC systems, replace as necessary.
    Pull the plugs from the low and high pressure switches, see if there is voltage to those, if not then, on the back of the compressor is the high pressure cut out switch, see if there is power to that one, if no power exists then, check for power to the relay, probably behind glove box ? ? ? Need a wiring diagram, a book is mighty handy. Might one of the members post in a diagram too, an innernet search could also provide one. Look for the relay, with all the proper color of wires. Be sure there is power to that one, should be power to two of the wires, with relay removed, if so then, try a relay, from a different circuit that has the same numbers, see if there now is power to that "High Pressure Cut Out Switch". If so, plug it all back together and check the operation.
    If no power to two of the relays terminals then, recheck fuses, check for broken wire.
    If fuse blows, unplug the compressors clutch coil. two wires right behind the pulley, install a new fuse and see if it still blows, if not then, replace the clutch, sometimes, compressor with a new clutch is almost as cheap as a new clutch. Takes some special pullers to replace the clutch, might be able to rent them but, they are not awfully expensive to buy.
     
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  5. JungleRamen

    JungleRamen Member

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    Thanks for all the welcomes and tips.
    The AC was running at full tilt just fine, and then all of the sudden started blowing hot air instead of cold.
    I checked my Haynes manual, but they just talk about recharging and say it's best to leave it to the pros.
    I did'nt find anything in it about a Fuse being the possible cause, so I guess I'll go get my Owners Manual and see if I can find what Fuse might be the cause.
     
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  6. JungleRamen

    JungleRamen Member

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    Checked the fuses and they are good to go.
    I think that since it happened suddenly, it is likely a leak or the compressor is dead.
    I'll take it in to the shop as soon as I can and let them figure it out.
     
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  7. MrMarty51

    MrMarty51 Full Member

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    If You have a multimeter or, a probe/test light then, check for 12 volts at anyone of the pressure switches, it could be a relay and, if so, it would save You some big dollars.
     
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  8. JungleRamen

    JungleRamen Member

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    #8 JungleRamen, Jul 22, 2015
    Last edited: Jul 22, 2015
    Where are these pressure switches located?
    The "Pressure Cycling Switch" that has the wires coming out of the accumulator?
    Just checked that, and though I have an Analog Multimeter, it reads 12ish V.

    Stuff I worked on in the Army did'nt have AC, so this is a new system for me.
     
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  9. MrMarty51

    MrMarty51 Full Member

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    I figured that You would have a pretty good meter, being that You were a military vehicle repair person.
    Now, with 12 volts being supplied to any one of the switches, lets You know that, the fuses and relay is working.
    You might be able to rent a leak detector from one of the parts stores, see where and IF there are any leaks, repair/replace components as necessary and, take it to a perfeshunal for the refill, or, take it to them for the complete check over and repairs.
    The pressure switches should be placed on the AC pipes and, possibly on the filter dryer"the canister looking thing". The smaller tubes/hoses is the pressure side, the larger hoses is on the suction side. Never, open the pressure side valve, on the manifold gauges, when charging the system. The only time that I will open the pressure side valve is when I am running the vacuum pump, to evacuate any moisture that may have gotten into the system from having open lines or, replacing components. The vacuum pump needs to be run for about two hours, to evaporate any humidity/moisture from the system, if the vacuum pump is not run for a long enough time then, there could possibly be moisture left within and, could freeze at the expansion valve, and, will not allow the effects of expansion to get the system as cold as it should.
    You might also go around the fitting with a set of wrenches and see of any of those are loose, tighten them up. Also, the orings within the fittings can become suspect after yeears of het and cold cycles. Those are the areas that are most often the cause of any leaks, if there are any.
     
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  10. JungleRamen

    JungleRamen Member

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    Thanks for all the Info!
    I used to have a decent digital MM but it got stolen.
    I appreciate all the advice, and you've helped me to understand the system much better.
    I'll leave it up to my service station guy.
     
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