95 Suburban k2500 a/c orifice tube

[1998_K1500_Sub]

So no one has real world experience with a Ford or variable orifice tube with rear air then?

@L31MaxExpress has dual air in his Express van, and I believe he's messed with the variable orifice tube at one time or another.

It was black gunk. I'd love to replace everything in this suburban system but I don't really enjoy pulling the dash.

I'm willing to bet your rear TXV is plugged too; it's got a screen on it for such things.

My thoughts:

- those rear refrigerant lines lie low in the system and might be accumulation points for debris; too, trying to flush crap out of them might be tough because it's an uphill battle. The last I looked, replacement lines weren't overly expensive. Consider it.

- flushing the rear evap / TXV... might be do-able and effective if you can remove them and separate them, but in my experience their fittings to NOT likely to come apart. I took mine out with a hacksaw.

On my 1998 Sub, I replaced everything but the front evaporator; it's easy to flush when the lines are disconnected (fortunately I didn't have a system with black gunk / debris, so I was willing to keep the front evaporator)

While I was replacing the AC lines, I also replaced all the rubber sections of the rear coolant circuit (for rear heater). It was easy to do them all at once. See https://www.gmt400.com/threads/95-suburban-rear-heater-hose-questions.53581/post-1201290

$0.02

 

[L31MaxExpress]

@L31MaxExpress has dual air in his Express van, and I believe he's messed with the variable orifice tube at one time or another.



I'm willing to bet your rear TXV is plugged too; it's got a screen on it for such things.

My thoughts:

- those rear refrigerant lines lie low in the system and might be accumulation points for debris; too, trying to flush crap out of them might be tough because it's an uphill battle. The last I looked, replacement lines weren't overly expensive. Consider it.

- flushing the rear evap / TXV... might be do-able and effective if you can remove them and separate them, but in my experience their fittings to NOT likely to come apart. I took mine out with a hacksaw.

On my 1998 Sub, I replaced everything but the front evaporator; it's easy to flush when the lines are disconnected (fortunately I didn't have a system with black gunk / debris, so I was willing to keep the front evaporator)

While I was replacing the AC lines, I also replaced all the rubber sections of the rear coolant circuit (for rear heater). It was easy to do them all at once. See https://www.gmt400.com/threads/95-suburban-rear-heater-hose-questions.53581/post-1201290

$0.02

Good memory. The Express van has one currently. I have also used the 0.062" Ford red tube with good results in the van. The factory White 0.072" tube gives poor cooling at idle.

 

[muddy94chevy]

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well that's one of my problems, double of some stuff is great dual orifice tube is probably not one of them. The one that enjoyed its stay and didn't want to come out was in the condenser. The one on the left I replaced probably after the original compressor bearing went.

 

[muddy94chevy]

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Nice thing is, haven't ran this compressor yet. Just installed it in the fall with the factory plug threaded in and the electric clutch unplugged. I get the gunk has to be the compressor, but they all still held pressure and turned reasonably easy. So I didn't think the compressors failed. It literally always been just the pulley making noise and one time had slop. Nice thing is I've replaced my rear lines and evap and txv altho it was some moons ago. Maybe 4 years. Hopefully they will unthread if I decide to replace them again. Tearing that apart is better then the dash but still not really enjoyable. Wonder if I could disconnect the rear suction line and put a scope up in there and see what it looks like. The condenser looks bad which is why I'm replacing it, but even with dual OT the air wasn't terrible. You were cool here in ohio and just comfortable in myrtle beach on July 4th. But I don't want to keep going through this either. I appreciate all the help this far. So l31, do you think it's worth the variable valve for the suburban? Or should I stick it in my 94 crew cab when it comes in? Or does it really make that big of a difference and buy 2 vov? Thanks!

 

[L31MaxExpress]

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well that's one of my problems, double of some stuff is great dual orifice tube is probably not one of them. The one that enjoyed its stay and didn't want to come out was in the condenser. The one on the left I replaced probably after the original compressor bearing went.

A system with rear ac should only have 1 tube. The rear has an expansion valve. The condenser mounted orifice tube is not used on a dual ac system. On my 99 Tahoe the front orifice tube is in the liquid line after the lines T off on the passenger inner fender.

VOV made a big difference in my 97 van on warm days and initial cool down.

Pressures run great and the AC gets ice cold. Granted R134a is not my personal choice of refrigerant on my stuff that I service myself. Digital pressure/temperature setup should give you an idea. T1 is reading the suction line at the compressor manifold, T2 is reading the discharge hose at the compressor manifold, EV is the theoretical evaporation temperature based on pressure and CO is the theoretical condensing temperature based on pressure. Even on a 105F day the high side discharge pressure and temperature are well under Sandens published continuous duty recomendations and their intermitent prolonged idle ratings are much higher. So no risk of compressor damage. In the same weather the stock as GM built it R134a system would nudge 325-350 psi with 60F vent temps at idle. The low side was lucky to pull down to 55 psi.

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[L31MaxExpress]

This measurement was outlet of the suction line off the accumulator and the liquid line just ahead of the orifice tube. The liquid line has good subcooling and the suction line has adequate superheat to boil off the liquid refrigerant. Critical charge volume will change in the system when you make system changes such as change the condenser design and mess with the orifice flow restriction. My system took less refrigerant with the smaller parallel flow condenser, sanden compressor and VOV to properly operate. Which was already only like 60% of the R134a system charge prior. It cools well on like 50% of the stated factory 4.25 lbs charge.

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[muddy94chevy]

My rear lines did not want to bust loose. Might just try and flush the best I can what I can and then if this compressor goes again just plan on replacing the complete system. How hard is it to put a sanden compressor in? Which compressor is the r4? Is that the pancake one? That's on pre vortec engines?

 

[HotWheelsBurban]

My rear lines did not want to bust loose. Might just try and flush the best I can what I can and then if this compressor goes again just plan on replacing the complete system. How hard is it to put a sanden compressor in? Which compressor is the r4? Is that the pancake one? That's on pre vortec engines?

Yes, the R4 radial style compressor is the one called "pancake" or "biscuit". Mainly used on TBI and earlier models.

 

[muddy94chevy]

So is the sanden what's on the vortec ones?

 

[HotWheelsBurban]

So is the sanden what's on the vortec ones?

I think what the Vortecs came with is a Delco DA6, but many have retrofit the Sanden. My Burb hasn't had functional AC since I got it, and it works okay on the crew cab (at least in the front seat, whoever decided the only duct facing the back seat should be behind the cupholder, oughta be forced to sit back there on hot, humid gulf coast summer days!). And the truck has factory dark tint glass on the back doors and rear window, so that's not the issue. I think it probably could use a little more Freon but haven't had the $$ to have someone look at it.