Orifice tube sizing

[wschimberg]

So I have a old Cadillac which has a v i r eliminator kit on it. It also has a new sanden style compressor on it. I first charged it today and the high and low side pressures both seemed off. At idle the low side had 60 psi of pressure and the high side had 175 psi. The compressor outlet was warm to the touch but not hot. The pipe right after the orifice tube was cold. The suction hose on the compressor was colder though. What I'm wondering is if the evaporator is being flooded with liquid refrigerant because the orifice tube is too big. That would explain the high low side pressure and the low high side pressure. Or at least I think. If anyone has any opinions on this matter please help me out as I'm trying to figure out what to do. I'm wondering if this kit was made for a larger compressor that moves more volume, therefore this compressor needs a smaller orifice tube. But I'm just guessing at this point. Any help would be greatly appreciated here.

[tony1963]

Sounds like you have a 70s era GM vehicle that has been converted to CCOT (cycling clutch orifice tube) system.

They do work great but check two things. First, did you overcharge the system? Rule of thumb is to charge at about 80% of the R12 specs and go from there if needed. Second, most people on this board used to recommend the Ford blue orifice tube.

Make sure that the orifice tube is inserted the correct direction.

[wschimberg]

So it is a aluminum block without an inserted tube. It is just a hole drilled through the aluminum and it looks a little large. My problem is there isn't a orifice tube to change out but just a hole drilled in an aluminum block. Can I try to restrict that hole or should I try to replace it with an actual orifice tube?

[Tim]

I would contact the supplier of your products and ask them what the recommended refrigerant charge should be and what size the orifice is on their eliminator kit. If you know these things, post the information and your operating pressures. The 80% term is used a lot. I've never been a fan of this, as it often leads to an undercharged system. With a proper condenser, one should not have to undercharge an R134a system.

[tbirdtbird]

I would not be surprised if you end up going to a traditional orifice tube

[tony1963]

Regarding the 80% charge issue, if an old R12 system calls for 3.75lbs or R12, I will charge it to 3.0 lbs which is 80%. If the pressures and temperatures are not acceptable, I'll charge another .25 lbs or 4 oz. If no change, another 4 oz, and so on. If I see any degradation in performance along the way, I stop.

In most cases, I see best results at or near the published capacity.

[wschimberg]

Ok, so I talked to them and they said my fault could also be a small compressor. I bought a sanden compressor but it's so much smaller than the stock A6 compressor, is it possible the smaller compressor is at fault or should I play with my charge first?

[Tim]

What's the 4-digit model number of your Sanden? They make many models, all with different capacities.

[tbirdtbird]

The venerable massive A6 has a displacement of 207cc.
Check the displacement of your pump. You did not identify exactly which year your Caddy was but most of the GM product line in that era were huge, meaning needing lots of cooling capacity. I suspect you will not be happy with a smaller displacement pump. All the components in an AC system are matched

[tony1963]

As a rule of thumb, the A6 is the top shelf of compressors. Yes, they're heavy and take a lot of power to run, but they move the refrigerant on those old systems.

Ford and Mercedes both used the GM A6 compressor in models in the 1970s and 1980s because of their superior design.