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1986 suburban a/c problems,
- Thread starter Jbhvnz
- Start date
Will L.
Well-Known Member
No, front valve. Rear system is working means rear system is fine.
Don't guess and then throw parts at it. Quick and dirty is to feel both front evaporator lines and see if they are both cold. Not "cool" and "cold" but both same cold. Yes: stuck blend door etc. No: low refrigerant charge or restriction like in the front orface tube.
I believe 1986 had vacuum door actuators so a broken age rotted hose, diaphragm, or connector including one left off the engine or vacuum tank is suspect. What a mess that system was and good luck tracking it down.
Is this still an R12 system? Suggest you keep it R12 if it is.
Word: It's likely cheaper to take this to a AC shop for a diagnosis, $100, than to throw $100 of quick fix products at it like recharge cans with guage kits.
I believe 1986 had vacuum door actuators so a broken age rotted hose, diaphragm, or connector including one left off the engine or vacuum tank is suspect. What a mess that system was and good luck tracking it down.
Is this still an R12 system? Suggest you keep it R12 if it is.
Word: It's likely cheaper to take this to a AC shop for a diagnosis, $100, than to throw $100 of quick fix products at it like recharge cans with guage kits.
Will L.
Well-Known Member
What are the gauges reading and at what outside temp
Morning 85-90 degrees, dual elec fans(condensor) plus new flex fan on engine, low side 35-40 high side 225-250, while charging, rec/dryer is cold, after charging rec/dryer gets warm, rear air works, the only old part left is rear expansion valve, will remove valve and see if its stuck open
Uncommon for today but back then AC was an option... Do you have an aftermarket AC system? If so the TXV for the front is likely stuck shut. I am splitting hairs because it makes a difference with the rec/dryer term vs. accumulator.
Otherwise factory had an accumulator (vs a rec/dryer) and an orface tube for the front. In this case the orface tube is either clogged, doubled up, or you have a low charge. Even "ice" clogging the orface tube from moisture in the system is possible. How much refrigerant did you put in the system?
Any ice spots you can see on the lines for the front AC?
Even if the rear TXV stuck wide open it would only slug the compressor to death IF the rear fan was off. This is not your problem.
Did you just repair this AC system from a bad compressor? Add AC that was missing parts for a long time? Did you replace the orface tube? The rec/dryer or accumulator new?
Did you use a VOV variable orface tube by chance? I have had a few of those VOV's plugged solid from the factory.
Otherwise factory had an accumulator (vs a rec/dryer) and an orface tube for the front. In this case the orface tube is either clogged, doubled up, or you have a low charge. Even "ice" clogging the orface tube from moisture in the system is possible. How much refrigerant did you put in the system?
Any ice spots you can see on the lines for the front AC?
Even if the rear TXV stuck wide open it would only slug the compressor to death IF the rear fan was off. This is not your problem.
Did you just repair this AC system from a bad compressor? Add AC that was missing parts for a long time? Did you replace the orface tube? The rec/dryer or accumulator new?
Did you use a VOV variable orface tube by chance? I have had a few of those VOV's plugged solid from the factory.
Factory1986 suburban w/rear ac, had poorly working r12, replacedr4 compressor, replaced evaporator , replaced rec/dryer ,replaced orifice tube with non varible, high ambient(105f and above)replaced every oring front to rear, replaced dual line from compressor to condenser and to evaporator. New 134 clutch cycle switch, While charging with 60 ounces of 134 the rec/dryer gets cold while taking the charge , as soon as low side pressure comes down the rec/dryer gets warm, yet rear ac works well
Will L.
Well-Known Member
Will L.
Well-Known Member
I can’t find the chart I am used to working off of. Grabbed this at random from google search.
verify this chart by comparison to a few others (online stuff often wrong) and make sure they are on the refrigerant you are running. This is for 134a.
You have an operational problem like low refrigeration amount, and possibly something else going on. Solve the issues first. Then later when you want the 134a to perform like the r12 did, get a new condenser and evaporators... ship them to Twisted Steel Performance for TLTD coating. The coatings will improve the efficiency by 30%, which btw is the variance between 134a and r12. Providing the rest of your system is correct it will cool to the same temp r12 used to.
You said you just bought new radiator iirc (i might be thinking someone else). remove it, rinsed out and ship to him at same time to improve its performance as well. Just too bad you didn’t come here before installing the new parts or would have told you then. Worth the effort long term imo.
verify this chart by comparison to a few others (online stuff often wrong) and make sure they are on the refrigerant you are running. This is for 134a.
You have an operational problem like low refrigeration amount, and possibly something else going on. Solve the issues first. Then later when you want the 134a to perform like the r12 did, get a new condenser and evaporators... ship them to Twisted Steel Performance for TLTD coating. The coatings will improve the efficiency by 30%, which btw is the variance between 134a and r12. Providing the rest of your system is correct it will cool to the same temp r12 used to.
You said you just bought new radiator iirc (i might be thinking someone else). remove it, rinsed out and ship to him at same time to improve its performance as well. Just too bad you didn’t come here before installing the new parts or would have told you then. Worth the effort long term imo.
The accumulator temp isn't as important as the evaporator line going into it esp. at idle. Is this line also warm?
Your system acts like there is a clog in the front evaporator circuit. I have heard of internally corroded evaporators, but, never seen one. The 105 degree reference is for the VOV's I love, but, have found some to be 100% defective from the factory: plugged solid. Charged the system and the low side went to 35 PSI, cut off and never changed. Show's over, period. That was a front AC system only. I have run the regular $1.99 orface tubes since.
May have to try and see if you can blow something through the front system with the orface tube removed. Compressed air, coughrefrigerentcough, dry nitrogen, whatever.
Where is the front orface tube exactally in the system? Possible you may have two by mistake in the system like inlet of evaporator and outlet of condenser. New condensers ship with them installed sometimes. This will ruin your day if there is also one in the evaporator.
Your system acts like there is a clog in the front evaporator circuit. I have heard of internally corroded evaporators, but, never seen one. The 105 degree reference is for the VOV's I love, but, have found some to be 100% defective from the factory: plugged solid. Charged the system and the low side went to 35 PSI, cut off and never changed. Show's over, period. That was a front AC system only. I have run the regular $1.99 orface tubes since.
May have to try and see if you can blow something through the front system with the orface tube removed. Compressed air, coughrefrigerentcough, dry nitrogen, whatever.
Where is the front orface tube exactally in the system? Possible you may have two by mistake in the system like inlet of evaporator and outlet of condenser. New condensers ship with them installed sometimes. This will ruin your day if there is also one in the evaporator.
- Staff
- #13
What did you put back in it? R4 replacement compressors have a poor reputation at best. You cannot use the variable orifice valve in a dual air system. Several of us have tried it and learned it wil fight with the rear units txv. For a dual unit running r134a, run a .062 orifice in the front, and be certain you have a TXV in the rear that does NOT fully close off. Otherwise never turn the AC on without the rear blower fan on. If you upgraded to a parallel flow condenser(I sure hope you did as serpentine and even piccolo condensers are not efficient enough for r134), you have to reduce the charge amount from stock. Just did a 88 square body, with a stock condenser it held 45 ounces roughly using the 80% charge rule, but it now only holds 38 ounces.
And do you happen to remember how many plate and fins were in your evap? I put a GPD in the one I just did and it had 2 more sets of plate/fins in it than the stock one for increased surface area to help improve efficiency with r134.
Rear cools and the front doesn't is normally low on charge. The TXV will open to provide Superheat to the rear, but there isn't enough charge for it to also provide refrigerant for the front unit. But the variable orifice valve cycling can also cause this to happen. Stock your front orifice was a .072, most go down to a .067 when going r134 since the R12 system isn't efficient enough for r134, so the drop in orifice helps to offset this some. GM found in 96 that a .062 worked better in dual air units.
I like to charge by feeling the line temps myself. You have to have a temp drop going through your condenser, if it's not shedding heat, it can't make cold air. By feeling your suction lines you can tell where your refrigerant is boiling to gauge how full the system is.
I know you said you have electric fans, but are they high quality fans? Cheap fans will not do the job of getting air through the cooling stack. 98-02 Camaro fans are a good fit for 28" core radiators that move alot of air. I also STRONGLY recommend installing a trinary switch. R12 systems did not have high pressure cutout switches, but r134a systems must have one. And a trinary switch will give you a high pressure cutout, liw pressure cutout, and electruc fan trigger so you don't burn your fans out prematurely.
And do you happen to remember how many plate and fins were in your evap? I put a GPD in the one I just did and it had 2 more sets of plate/fins in it than the stock one for increased surface area to help improve efficiency with r134.
Rear cools and the front doesn't is normally low on charge. The TXV will open to provide Superheat to the rear, but there isn't enough charge for it to also provide refrigerant for the front unit. But the variable orifice valve cycling can also cause this to happen. Stock your front orifice was a .072, most go down to a .067 when going r134 since the R12 system isn't efficient enough for r134, so the drop in orifice helps to offset this some. GM found in 96 that a .062 worked better in dual air units.
I like to charge by feeling the line temps myself. You have to have a temp drop going through your condenser, if it's not shedding heat, it can't make cold air. By feeling your suction lines you can tell where your refrigerant is boiling to gauge how full the system is.
I know you said you have electric fans, but are they high quality fans? Cheap fans will not do the job of getting air through the cooling stack. 98-02 Camaro fans are a good fit for 28" core radiators that move alot of air. I also STRONGLY recommend installing a trinary switch. R12 systems did not have high pressure cutout switches, but r134a systems must have one. And a trinary switch will give you a high pressure cutout, liw pressure cutout, and electruc fan trigger so you don't burn your fans out prematurely.
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- Staff
- #14
GPD's parallel flow condensers come already coated. Just put one in and have a picture of the coating on it. Here it is setting next to a stock serpentine.
The orifice goes in the evap, it cannot go in the condenser in a square body.
- Staff
- #15
Just looked up the factory charge amount for a dual air square body 85+ Burb and it was 96 ounces(6 lbs) of R12. If you still have the stock condenser, assuming the customary 80% charge rule, 60 ounces would be quite a bit under charged as it would hold 77 ounces. If you put in a parallel flow condenser, going off the reduction in charge I experienced, you would need 70 ounces to charge it. You can see how what was replaced and what wasn't can effect things.
P
C/o parts is not a problem, this is my retireme nt truck, I don't think I mentioned it there are not very many old parts left on this truck, bumper to bumper I think the steering box is yet to be changed but not much more. Everything i found online said 72 ounces of r 12, so i put in 60 ounces. Pulled out 134, will replace txv, had floating high side pressures220 to 125, will get a new orifice spec for 86 burb w/rear air 134a not high ambient. Let ya know, it will be a few days. Jim
- Staff
- #19
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.
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.
- Staff
- #20
Should be 13 ounces I believe for a dual air square body. Problem is the R4 I believe only like pag 150, and pag 150 is not good for performance. Pag 46 works much better and doesn't liquid slug as badly, it stays more fluid in the lines instead of getting caught in the evap or suction line when it gets cold. I believe this is why GM superceded most compressors from pag 150 to pag 46 around 05.