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Finally got the A/C working(PIC'S)

Discussion in 'The Garage' started by BobK, Jul 19, 2004.

  1. BobK

    BobK 1/2 ton status

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    Finally got the A/C working(PIC\'S)

    Well I had rebuilt my A/C and heating system about 5 months ago but never got around to getting the A/C working.

    I got er done last week though.

    I retro'd the system from R12 to R134a and got rid of the POA valve.
    I used a POA eliminator from Old Air Products.Along with a fixed orafice tube(FOT) and a pressure cutout switch.

    The system cools O.K.,still some fine tuneing needed but I get about 50F at the vents.Not bad but I'd like it colder.

    Here's a few pic's of the process.

    This is the connection to the low pressure side of the system.That's the POA eliminator I had mentioned earlier.An integral pressure cutout switch comes with the POA eliminator.
    I just spliced into the existing A/C compressor wire.What it does is it shuts down the compressor and prevents the evap. from freezeing up.
    [​IMG]

    Here is the high side connection at the compressor.I used a Sanden SD5H14 compressor.
    [​IMG]

    I used is a RobinAir,1/2hp,6cfm vacume pump to evacuate the system before charging.
    [​IMG]

    The gauge set I used.This allows you to measure the vacume you pull on the system as well as the pressure in the system while chargeing it.
    In this pic I'm evacuating the system.The gauges are at -29.5inHg,which is as far as you can go on the planet Earth.
    [​IMG]

    The can tap I used.I ended up overcharging the system a bit.I used four(4),12oz cans of R134a to charge it up.
    [​IMG]

    Killin time while evacuateing the system
    [​IMG]

    I connected my can tap to my vacume pump via an adaptor I bought at Car Quest.This way I can eliminate the chance of air getting in the system when I have to change cans during the charging process.
    [​IMG]

    I had to "jump" the cutout switch during the first bit of charging.The compressor would not engage untill some pressure was in the system.
    [​IMG]

    Just an overhead view of things.
    [​IMG]

    This is the top tube of the evaporator core.Condensing like it should,cool to the touch but not iceing up.
    [​IMG]

    And the bottom line.The line on the right is the FOT.It meters the amount of r134a that got through the evap. core.It function like the TVX valve on the old POA system.
    [​IMG]

    Like I said I still nedd to "tune" it a bit.Might need to put in a smaller FOT or take out a bit of R134a.Worst case would be a new parallel flow condensor.I have the orig. type in there now.Through the reading I've done the orig. condensor design may not work that well when retro'd to R134a.
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

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    Re: Finally got the A/C working(PIC\'S)

    Good write up. Nice to see the pics - it really helps understand what you did. Good job.
     
  3. sickquad

    sickquad 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    I'm about to do the same thing. I have so many questions to ask you. /forums/images/graemlins/bow.gif Hope you don't mind but be expecting a PM.

    -Chris
     
  4. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Re: Finally got the A/C working(PIC\'S)

    The new style Aluminum pump..... /forums/images/graemlins/thinking.gif
     
  5. wasted wages

    wasted wages 3/4 ton status

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    Re: Finally got the A/C working(PIC\'S)

    Hope ya flushed the system ,( to remove the mineral based oil from the R-12) changed ALL the o-rings and drier, and put the proper charge (amount and type ) of oil in the comp!
    BTW,,, what micron level did you pull the system down to? /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif
     
  6. BobK

    BobK 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    The system was open to the air for 5+ years.
    The only thing that was still there when I bought the truck was the POA and the evap. core.

    I used the POA eliminator and didn't reuse the POA.
    I got the Evap.core presure tested and flushed before I put it back in.

    All new o-rings,hard and soft lines,receiver/dryer,compresor and condensor.

    I don't have a micron gauge just a set of reg. dial gauges.
    They were pegged at the -30(I know that -30 is not possible) while I evacuated the system.

    I put 1oz of BVA-100 in the receiver/dryer and 6oz's in the compressor.

    I did overcharge the system though.I put in Four,12oz. cans and have come to realize that that was too much.
     
  7. K5 NUTT

    K5 NUTT 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    4 cans is to much...134a can be a tricky devil to play with....consider a vacum operated heater shut off valve to keep hot air away from the evap....you can also play with your choice of FOT's...the diff colors indicate orifice size...also i see it uses a gm low psi switch...so you can adjust that to let her pull down farther...rapping your suction line and accumulator can help also...allthough being a gen 1 i assume your drier is out on the core support and you will not have a accumulator...what kind of pressures are you running at 1200 rpm doors open on the high side? I believe for the gen 1's they make a retro condensor the disapates heat alot better...also gen 1's have lots of room to ad a helper fan on the condensor...as far as charge...i'd try 2.75lbs first then 3.00 and see which cools best....the old rule of thumb is 80 percent of the r12 charge.... but it really depends on how the each indivdual system reacts...but keeping that head psi down is the key! Run water over the condenser and you will see what i mean..

    DW
     
  8. BobK

    BobK 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    Well here's the latest.
    Evacuated the system again to start from scratch.

    Replaced the Orifice tube from a white GM one,with an orifice size of .72,to a Blue Ford orifice,sized at .67

    Pulled vacume for for 1hr x2 with 30 minutes inbetween.No leaks,presure stayed at -29.5.

    Added 2.5 cans(30oz) of R134a.

    At idle
    Low-40
    high-200-210

    vent temp 54F

    ambiant temp 2" infront of condensor-84F

    At about 1500rpm
    Low-30
    high-180

    Vent temp-52F

    Watered down the condensor and presures when to:
    Low-25
    High-140-150

    vent temp up to 60F

    I can't seem to break the 50F mark.

    Talking it over with a buddy,I have failed to mention that my 1st gen's top is off. /forums/images/graemlins/tongue.gif
    This is prob effecting the vent temps.I guess it's always trying to cool the ambient air temp instead of the already cooled inside air.

    I"m going to take one of the vents off tomorrow and feed it into the inside air intake.Maybe I can simulate how it will be with the top on this way.
    Worth a try anyway. /forums/images/graemlins/peace.gif

    Thanks for the suggestions though.
     
  9. Re: Finally got the A/C working(PIC\'S)

    I am working on rebuilding the ac in my Suburban and have decided to go with a parallel flow condenser. Supposedly they are better suited to R134, so I figure it can't hurt when converting from R12. I need to replace my condenser anyway as my system has the "black death", so almost everything will be new.
    A few weeks ago I help convert a 1977 Suburban to R134 and it cools good, but not great. But the factory condenser was used.
     
  10. BobK

    BobK 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    Well...good news
    Today I added 6oz. of R134a for a total of 36oz in the system.Had some good results with this change.

    Here's the data as of today(7/22/04)

    At about 1700rpm
    low=25
    high=peaked at 260
    vent temp-44-46F
    ambiant temp lower today=75F.
    fan on high
    Compressor cycled,on for 30sec,off for 5sec.

    at Idle(approx.700rpm)
    low=30-38
    high=180-230
    vent temp=44-46F.
    fan on high
    Compressor DID NOT cycle.

    Here's the kicker.
    I turned the interior fan on low and my vent temps dropped even more.

    at idle
    low=30
    high=180
    vent temp=38-40F.!!!!
    Compressor DID NOT cycle.

    At 1700 rpm
    low=25
    high=200-220
    vent temp=42-43F.
    Compressor cycled,on 30 sec,off 5sec.

    So I'm pretty happy with those vent temps.

    Thanks to those that made suggestions.

    Hope this info. can help others down the line.
     
  11. K5 NUTT

    K5 NUTT 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    Playing with the charge is the best way to get your system dialed in...

    That would be called sun load...which without a top is alot for the system to try and cool...as a general rule...R12-R134A job is to cool 40 degree's below ambiant...i would still run a helper fan on the condensor for those days you have to sit at a traffic light three times to get thru it....from experience in phoenix....lol.

    Parallel or serpintine design condensors are worth the money...and the effort to fab it in place...

    DW
     
  12. BobK

    BobK 1/2 ton status

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    Re: Finally got the A/C working(PIC\'S)

    Well I'm at a 35 deg. drop now.So I'm in the ballpark.

    I may still get a parallel flow condensor.The temp's here on the California coast rarely get past 85F.But when I move back Home(ontario,Canada) the summertime temps are ALOT higher and the humidity is a killer as well.
     

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