1986 suburban a/c problems,

[EWC]

I have a 91 Suburban with dual AC and can say that you need to run the rear with the front on . Makes a big difference in the cooling . Sounds like I need to see if the Otube is in the condenser as when I replaced it with a new one , there was not one installed . I did put one in the " original " position , guess I need to change that .

 

[EWC]

Ferm , what's up with the PAG stuff ? Can I add 46 to a system that I think I put the 150 in ?

 

[Jbhvnz]

The evaporator is new

The only specs listed for front orifice are for r12. The rear txv that worked with R12 does not work properly with r134 in a dual application. You have 3 or 4 different types of condensers for square bodies, and not all of them work well with r134. New parts do NOT mean GOOD parts. Once you start changing parts, factory charge amounts go out the window, then you have to check sub cooling and super cooling to determine your correct charge.

Your fluctuating high side is because you put a variable orifice valve in the front unit. When you do this, vov will cycle whenever the orifice tries to control flow, and when it cycles, it causes the other to cycle, and tbey start going back and forth fighting each other.

I've also found multiple evaporators available for the front unit, hence why I said we need to know EXACTLY what was put in it to help you with it. Otherwise there is nothing we can do.

There is slapping an AC system together, and then there is picking the right parts to make one work.

The orofice is NOT varible, but for high ambient temps, the evap is a factory replacement, the rear air works, the front is warm. I w

 

[Jbhvnz]

The orofice is NOT varible, but for high ambient temps, the evap is a factory replacement, the rear air works, the front is warm. I w

PS, after 38 years as a professional tech, the last 20 with the Caterpillar Proving Grounds in Green Vallet Az,NOTHING gets slapped together. I will let you know what I find

 

[WarWagon]

PS, after 38 years as a professional tech, the last 20 with the Caterpillar Proving Grounds in Green Vallet Az,NOTHING gets slapped together. I will let you know what I find

No offense is ever intended.

ASSumptions are made and hopefully corrected. You know we see all kinds of stuff on here ... we are not there and have to depend on you for seeing and telling us whats going on. AC systems tend to be the least understood in general.

 

[WarWagon]

Ferm , what's up with the PAG stuff ? Can I add 46 to a system that I think I put the 150 in ?

R4 compressors will DIE a very messy noisy death contaminating everything with it's ground up innards if you feed them the wrong oil. Even the ester oil for 'dirty R12 conversions' that don't flush the R12 mineral oil out will burn them up. I used the wrong ester oil on a factory 134a R4 compressor only once and got to do the job over in a short time. So use PAG 150 with R134a or alternate gasses and the original R12 oil if using R12. Some other newer compressors can use the lower viscosity oil: just not the 1970's POS inefficent R4 design that sucked even on R12...

 

[Jbhvnz]

No offense is ever intended.

ASSumptions are made and hopefully corrected. You know we see all kinds of stuff on here ... we are not there and have to depend on you for seeing and telling us whats going on. AC systems tend to be the least understood in general.

Sorry, its a work of love, and more of a restoration. A/C and cooling system tests were my favorite at work. The balance required to operate two systems off one pump makes this a very interesting problem, throw in a gas change and it makes you really think about what is happening inside the systems, good parts help. I will find the answer, let you know.

 

[THEFERMANATOR]

The orofice is NOT varible, but for high ambient temps, the evap is a factory replacement, the rear air works, the front is warm. I w

Orifice tubes don't care about ambient air temp and are not listed that way. GM used 1 orifice until the 90's, a .072, that was it. The VOV, or variable orifice valve IS listed by your expected ambient temps. From the parts stores you have a red/black for temps under 105, and a white/black for temps of 105+. So if you're buying one for an ambient air temp rating, it IS a VOV type. You can also tell by the price as a regular orifice is about $2 from the parts store(under a buck online), and variable units are $25-28(about $10-15 online).

I'm trying to help you here, but you're not really giving us anything to go on. As I posted before, there is 4 different factory replacement condensers that they say will fit(serpentine, serpentine capillary, piccolo, and parallel flow), only one of them is meant to work well with r134a. And I also held 2 different style front evaps in my hand with 1 having considerably more surface area to work better with r134a. The catalog only lists 1 orifice for the front and 2 different VOV's, but there is a better match out there that GM found later on. And there is only 1 txv listed for the rear, but again, there is better out there for r134.

But if you want help, you need to answer some of our questions like oil, which condenser, and so on.

 

[THEFERMANATOR]

I have a 91 Suburban with dual AC and can say that you need to run the rear with the front on . Makes a big difference in the cooling . Sounds like I need to see if the Otube is in the condenser as when I replaced it with a new one , there was not one installed . I did put one in the " original " position , guess I need to change that .

Square body condensers NEVER had an orifice in them and cannot accept one. That was gmt400's from the early 90's on(yes, not even all gmt400's had an orifice in the condenser). And the gmt800 went away from that design as well.

As to oil, use only double end capped pag oil, and preferably 150. Some have used pag 100, but most compressor builders say this is a huge no no with the R4. It sucks because pag 46 performs better and flows through the lines better. But the R4 compressor needs a heavy oil to hold up with the 4 large piston long stroke design.