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1967 Chevy truck: POA valve with a R4 comp.

67swb on Sun March 08, 2009 3:26 AM User is offline

Year: 1967
Make: Chevy
Model: c10
Engine Size: 350
Refrigerant Type: r134
Country of Origin: United States

After reading a ton of posts here I've decided to go with the factory A/C setup. I'm going to go with the biggest parallel flow condenser I can fit and adjust the POA valve down to 26 psi. I do have a couple questions I hope someone can answer.

1. I'm running a serpentine belt setup that uses a R4 compressor. So, I'd like to stay with it even though it probably isn't the best comp. out there. Someone does make brackets to adapt a Sanden comp. to the serpentine setup, so I could go that route if it is a better option. Out of those two which would work better in my app.?

2. Both of those are meant to be ran in a cycling system. Without using a POA eliminator, what options do I have to cycle the comp. or will that be a problem? Would a trinary switch work for this?

3. Either way I plan to use the trinary sw. to run a condenser fan. Where should it go in the system? Between the POA and comp.?

4. There is a guy on ebay selling a kit (expansion valve, POA valve) that coverts the system to a internal equalization system. Is there any benefit with this over the stock external equalization setup?

Thank you for your time!
Jay

bohica2xo on Sun March 08, 2009 6:59 PM User is offline

With a POA system, you do not cycle the compressor. The POA valve throttles the suction side to prevent evaporator freez-up, and the TXV throttles the evaporator inlet. This is a continous control system.

The sanden should do ok with suction throttling. Be sure there is enough oi lin the system, and that the oil bleed is woring corectly in the POA valve. The TXV / POA system is a great way to make cold air - much better than the "bang-bang" control of the CCOT systems.

I can't say how well the R4 will do with POA operation - they are not the best compressor GM ever built. Perhaps one of the others here has used an R4 sucessfully in a POA system. Guys?

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

67swb on Mon March 09, 2009 9:39 PM User is offline

Thanks bohica2xo,
How can I make sure the oil bleed is working right? I have tested the POA by blowing air through the TXV with a gauge on the low side and it's right at 30psi. I haven't adjusted it yet because I'm still not 100% on using r134. Is there a way to test the TXV? It is cheap to replace, but I don't like the EXTRA long coils on the new ones. If I stay with r12 will a PF condenser still help?

Anyone else know if the R4 comp. will work?
Thanks,
Jay

GM Tech on Tue March 10, 2009 8:56 AM User is offline

R-134a and the R-4 is the worst combination out there-- many replacements on '94-95 trucks -due to internal yoke wear- noise is the complaint- the yokes wear and the compressor knocks so loud you can hear it a block away. I never convert R-4s- keep them with R-12 and mineral oil--- or in your case, I would seriously consider the Sanden alternative-- unless you plan on replacing the R-4 ever other year or so.....

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

TRB on Tue March 10, 2009 11:04 AM User is offlineView users profile

Quote
Originally posted by: GM Tech
R-134a and the R-4 is the worst combination out there-- many replacements on '94-95 trucks -due to internal yoke wear- noise is the complaint- the yokes wear and the compressor knocks so loud you can hear it a block away. I never convert R-4s- keep them with R-12 and mineral oil--- or in your case, I would seriously consider the Sanden alternative-- unless you plan on replacing the R-4 ever other year or so.....

Agreed, GMtech why no love for the Seltec?

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

NickD on Tue March 10, 2009 11:54 AM User is offline

A6 was the best compressor GM has ever built, been all downhill since then, what's wrong with using that? And R-12 is still available, okay, so I am not keeping up with the times, but those were good times. Trying to add up the hundreds of thousands of miles I had R-12 with A6's without problems, has to be at least over 800,000 miles.

Now when the EPA banned R-12, demanded recovery, introduced R-134a with those stupid ports, aluminum condensers, poor GM seals, rotten evaporator cores, that's when I started having problems.

Edited: Tue March 10, 2009 at 12:00 PM by NickD

TRB on Tue March 10, 2009 2:58 PM User is offlineView users profile

I would take a Valeo/Seltec TM16 or TM21 before I would use an A6 with R134a in this case. Now the new A6 replacement hitting the streets would be a great option also.

10H20 - A6 Replacement

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

steve325is on Tue March 10, 2009 3:12 PM User is offline

The OP is running a "later" model serpentine belt setup, so an A6 is not an option for him.

-- Steve

CorvairGeek on Tue March 10, 2009 6:32 PM User is offline

Considering that the POA was only used with a compressor with a sump (A6), wouldn't a POA with an R4 and R134a be potentially even worse than '94-95 trucks due to oil starvation?

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Jerry

NickD on Wed March 11, 2009 6:30 AM User is offline

Quote
The OP is running a "later" model serpentine belt setup, so an A6 is not an option for him.

As a purest at heart, can only thing stock, liked those multiple belt systems, if compressor problems, just remove that belt and you can keep on driving. Another reason why the A6 lasted so long was the clutch only engaged once for a trip, not this constant zero 0-2,500 RPM instant acceleration every 10-30 seconds. Was a load demand system, cooler outside and a lot less load on the engine.

With a fully loaded Buick with an over 400 CID engine in it tipping the scales at 6,000 pounds would always get 20 mpg in good tune, an OD transmission would have helped that. They sure can't claim that today some 45 years later even with all this electronic crap. Only reason why GM dropped the POA system was to make the stockholders happy, so convince me they have made progress.

One bit of progress, is with one little fouled spark plug or plugged injector, the dash will light up like a Christmas tree, and the damned thing won't run and the things will cost you a second mortgage to repair it.

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