Automotive Air Conditioning Information Forum (Archives)

pippo on Tue September 11, 2012 4:13 PM

Year: 87
Make: alfa romeo
Model: spider veloce
Engine Size: 2L
Refrigerant Type: r134a
Ambient Temp: 90-95
Pressure Low: 47-40
Pressure High: 100

people,

My alfa is showing psi's described above, and ac is very cool, but I would say not cold. About 48 deg F. I noticed high PSI is only about 100-105 or so. Isnt this way too low for a compressor?? Could that be the suspect for why my cooling is not very cold? Shouldnt a comp high side show more like 180-200psi?

Thaks

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ice-n-tropics on Tue September 11, 2012 4:57 PM

Pip,
You don't have low charge (suction pressure is high) or air in system (Pd is low) or bad TXV.
Your Veloce convertible pressures indicate some inadequate suction or discharge valve closure in the wobble plate compressor. In 87 the valve plate to block gasket was rubber covered metal (not asbestos fibre), therefore it is unlikely you have a blown gasket between cylinders. foreign material stuck under a valve (loose desiccant, piston or ring wear particles, or chip of hose material) could result in a 50% pumping loss as you describe.
First step is to block air flow through the condenser and see if the discharge pressure will climb to 300 psi. If so the compressor is OK.
If pressure stays below 200 psi, remove the compressor head bolts and valve plate and find the root cause.
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
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pippo on Tue September 11, 2012 7:51 PM

OK, ice. I could try blocking the cond. Whats the best way to do that? Never did that before.

Oh, I should have stated above that psi for low side was 47-50, NOT 47-40 (typo). Also, what is Pd? Palladium?

I tell ya man, if its the comp, Imbuying new/reman, not messing wiith the innards. Im a decent ac guy, but not a pro with all the tools..... But thanks, still.

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Edited: Tue September 11, 2012 at 7:52 PM by pippo

mk378 on Tue September 11, 2012 9:23 PM

Cut out a piece of cardboard to fit in front of the condenser.

Pd is discharge pressure-- high side pressure.

ice-n-tropics on Wed September 12, 2012 12:35 PM

Hi Pip,
You can do anything you put your mind to, including remove the valve plate assembly. That would not only satisfy my curiosity, it would also show if you have a deteriorated hose or require a flush.
You've been around TRB's A/C grad school long enough to give it a shot. What do you have to lose?
In any case, avoid reman Sanden comps.
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

pippo on Wed September 12, 2012 4:57 PM

Thanks, again, people. geez, Ice, thanks for the gracious compliment, but still, I dont pretend to know a lot, just some. Still, I may take you up on the offer to open up the innards if I get a chance, and if necessary.

MK, I might try the cardboard trick. (Oh, guys, I did say my high side was 100 psi in post #1)

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pippo on Sat September 15, 2012 2:01 PM

Man, now you wont believe it, but drove the car and with ac ON, whenever at idle (say, at red light, stopped, or even driving very slow in traffic, going 5-10 mph, low revs), engine quits!! yeah, whenever engine rpm's dip down engine stops dead- I have to start it again, of course, with ac off. Driving/idling at red light with ac off, no problem. (I havnt had a chance to try the "cardboard in front of condenser" yet, although, now it may not matter)

man, doesnt this mean compressor is producing tooo much of a drag on engine crankshaft? (for now, Im not even gonna run the ac- hate to cause a catastrophe....)
Thanks, people.

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Edited: Sat September 15, 2012 at 2:02 PM by pippo

mk378 on Sat September 15, 2012 7:09 PM

See if the compressor turns OK by hand. Usually this is a problem with the engine controls not the A/C.

But it's a bad idea to run any system that is not working properly.

pippo on Sun September 16, 2012 9:10 AM

You mean by just trying to turn, by hand, the clutch on comp? (of course, the belt is on comp pulley, and should be stiff since its attachec to the crank shaft pulley)......

Clutch should spin freely, MK?

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pippo on Tue September 18, 2012 5:02 PM

OK, just wanted to follow up as promised- the clutch face/plate does not budge. Guess its time. Now, why did ice say avoid sanden remans? Even from good supplier? Of course, I will consider new- need to look up what this site sells them for. Wasnt sure if they are Sanden 508's or 507's.......I will check the shop manual......

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beware of the arrival