Need AC help why compressor doesn't engage 70 GS with POA valve

Discussion in 'The Big Chill' started by fanofsteel, Jun 5, 2021.

  1. fanofsteel

    fanofsteel Active Member

    Excuse my ignorance as I don't have a lot of knowledge of AC systems and need some help.

    I have a 70 Buick GS455 that was converted some time ago to R134 and has a POA valve installed. There is
    voltage (measured 11.75 volts) to the one side of the POA valve with engine running with AC on. However the compressor never engages. If I hot wire directly from battery to the hot side of the compressor, the compressor engages and spins.

    At this point I decided that perhaps the POA valve was maybe bad, so I bought a new one from Old Air products along with a new drier. I drained the system, put a vacuum pump on it for an hour, put new seals on these two parts I replaced and recharged the system with 3.75 lbs of R134. I had to hot wire the compressor to get the R134 into the system.

    The compressor still doesn't engage normally unless its hot-wired directly. What can I try next?

    Len
     
  2. mikec

    mikec Well-Known Member

    Sounds like you are running a POA replacement with a cycling switch versus a true POA valve. If you getting voltage to only one side of the switch, then the switch is adjusted too high. It is set to break in a drop in pressure and should break around 35 psi or so. It also can mean the switch is defective or it isn’t mounted or screwed on correctly
     
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The first place I would look is the switch on the dash. When you rotate that switch up to A/C, it pushes together 2 contacts to engage the compressor clutch. I had a switch on my first Buick (72 Skylark) actually partially melt. You need to get to the back side of that switch and check both sides of those contacts to see if they are working. You may be able to see it with a mirror if you remove the radio completely.
     
  4. fanofsteel

    fanofsteel Active Member

    Mike and Gary, I appreciate you both for replying and trying to help me. Due to some health issues, I haven't been able to get back to this.

    Mike, my apologies, you are correct and I should at least be using the correct terms(instead of a true valve).

    I bought these for my 70 GS455 :

    https://www.oldairproducts.com/product/50-2551a-poa-update-kit/

    https://www.oldairproducts.com/product/90-7201-o-ring-kit

    https://www.oldairproducts.com/product/21-4213s-receiver-drier

    For this discussion, I'll refer to it as the 'POA switch'

    Gary, I always get +12 volts to the one side of the POA switch when the AC switch is up and on. So, the voltage is always getting to the switch.

    I didn't record/write down the actual pressures and I guess that might be the next logical step I need to take and report back on them.

    I'm open to any suggestions as I haven't done anything since this post, thanks

    Len
     
  5. mikec

    mikec Well-Known Member

    Sounds like you had the same switch I had and then gave up and went back to the factory POA setup. On that switch is a screw that adjusts the point that the switch makes and breaks. Try turning it and see if it makes. That will send voltage to the compressor coil. I think clockwise increases the pressure where it makes but my memory ain’t what it used to be
     

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