Author Topic: 90 burb ac issue  (Read 3520 times)

Offline topp

  • Frequent Member
  • **
  • Posts: 498
90 burb ac issue
« on: July 28, 2019, 10:13:38 PM »
So my 90 burb with rear ac has been killing me. New parallel condenser, new evaporator both front and rear, new accumulator, hoses, expansion valve, orifice tube and compressor. 
In 3 attempts,  0 success. First 2 times, vacuum applied, held for 30 min. Added 80% of r12 amount of r134 with 10 oz pag 150, compresser cooked in under 20 minutes.
3rd attempt at a shop, same result.

Compressor is running at 205 degrees, no matter the amount of pag or r134 charge.  Shop attempted to block off rear ac and charge front. Charged like a single system and high pressure side climbs and climbs until the valve on back of compressor vents.


Anyone have any suggestions???
I NEED ac in this beast with heat indexes over 105.
'90 Suburban TBI 350

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #1 on: July 29, 2019, 12:11:53 AM »
What is a parallel condenser?  Did you mean to say serpentine?  Did you account for the oil shipped in the compressor before topping off the oil?  What are the high side and low side pressures?  What is the ambient temperature?  What is the center outlet nozzle temperature on high blower at ~2,000 engine RPM?  Did you try flushing the condenser?  What is the condition of the condenser and radiator fins?  Is airflow through the condenser/radiator obstructed (e.g., smashed fins, bugs, birds, rodent midden, dirt or other debris)?  Is the fan clutch operating correctly?  Are the drive belts adjusted correctly?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

  • Frequent Member
  • **
  • Posts: 498
Re: 90 burb ac issue
« Reply #2 on: July 29, 2019, 01:34:32 AM »
What is a parallel condenser?  Did you mean to say serpentine?  Did you account for the oil shipped in the compressor before topping off the oil?  What are the high side and low side pressures?  What is the ambient temperature?  What is the center outlet nozzle temperature on high blower at ~2,000 engine RPM?  Did you try flushing the condenser?  What is the condition of the condenser and radiator fins?  Is airflow through the condenser/radiator obstructed (e.g., smashed fins, bugs, birds, rodent midden, dirt or other debris)?  Is the fan clutch operating correctly?  Are the drive belts adjusted correctly?

Parallel flow condenser. Better than the old style. It is a serpentine setup. Compressor came dry. Added 11 oz as recommended in the instructions,  8 for compressor,  1 for each evaporator, 1 for accumulator. First 2 times low pressure  was at 30-40 and high at 350 with ambient temp at 105. Condenser is new. No obstruction s in front, everything is adjusted right.temp at vent never below 78. Never got off idle. Basically a new system except for lines to rear which I flushed.
Shop even flushed the system and got same results. They couldnt figure it out.  At wits end.

Could it have been a bad new compressor x3?

Sent from my SM-G955U using Tapatalk

« Last Edit: July 29, 2019, 01:38:17 AM by topp »
'90 Suburban TBI 350

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #3 on: July 29, 2019, 09:23:48 AM »
With gauges connected, engine running at ~2,000 RPM, thermometer in the center outlet nozzle, doors/windows closed, blower on high, and A/C on MAX, spray water from a garden hose across the condenser.  Allow the system pressures and outlet temperature to stabilize.  Continue spraying the condenser with water.  What do the system pressures and thermometer measure?  Use the chart below for comparison.  Knowing the relative humidity is important.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

  • Frequent Member
  • **
  • Posts: 498
Re: 90 burb ac issue
« Reply #4 on: July 29, 2019, 01:38:55 PM »
With gauges connected, engine running at ~2,000 RPM, thermometer in the center outlet nozzle, doors/windows closed, blower on high, and A/C on MAX, spray water from a garden hose across the condenser.  Allow the system pressures and outlet temperature to stabilize.  Continue spraying the condenser with water.  What do the system pressures and thermometer measure?  Use the chart below for comparison.  Knowing the relative humidity is important.
Humidity was around 75%. Air temp 97, heat index 105.


Sent from my SM-G955U using Tapatalk

'90 Suburban TBI 350

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #5 on: July 29, 2019, 02:14:02 PM »
With gauges connected, engine running at ~2,000 RPM, thermometer in the center outlet nozzle, doors/windows closed, blower on high, and A/C on MAX, spray water from a garden hose across the condenser.  Allow the system pressures and outlet temperature to stabilize.  Continue spraying the condenser with water.  What do the system pressures and thermometer measure?  Use the chart below for comparison.  Knowing the relative humidity is important.

You need to perform this ^^^^^ to continue.  Also, see the chart below in reference to your stated parameters.  This is what you should anticipate according to GM for your year/model vehicle.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

  • Frequent Member
  • **
  • Posts: 498
Re: 90 burb ac issue
« Reply #6 on: July 29, 2019, 02:20:41 PM »
With gauges connected, engine running at ~2,000 RPM, thermometer in the center outlet nozzle, doors/windows closed, blower on high, and A/C on MAX, spray water from a garden hose across the condenser.  Allow the system pressures and outlet temperature to stabilize.  Continue spraying the condenser with water.  What do the system pressures and thermometer measure?  Use the chart below for comparison.  Knowing the relative humidity is important.

You need to perform this ^^^^^ to continue.  Also, see the chart below in reference to your stated parameters.  This is what you should anticipate according to GM for your year/model vehicle.
I know. I had the chart. So did the shop.
3 times the high pressure just kept climbing up until it blew out the vent on the compressors. 3 times the compressor overheated. 12 oz. Pag oil and 80% of what the system called for. All 3 times lines flushed. All 3 times it never blew cold. All 3 times within pressure specs.
Compressor each time overheated at 205 degrees.

Looking for cause of compressor over heating.

New condenser, 2 new evaporator, new orifice tube, new lines, new accumulators, and 3 new compressors.

Sent from my SM-G955U using Tapatalk

'90 Suburban TBI 350

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #7 on: July 29, 2019, 04:00:55 PM »
LOL 

I got what you are telling me.

There is a very specific reason for running cold water across the condenser.  Did you or the shop do this?  What were the results?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

  • Frequent Member
  • **
  • Posts: 498
Re: 90 burb ac issue
« Reply #8 on: July 29, 2019, 04:07:08 PM »
They did. Results were pressure in spec.
Compressor running at 205 degrees
78 degree air out of vent

Sent from my SM-G955U using Tapatalk

'90 Suburban TBI 350

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #9 on: July 29, 2019, 04:39:27 PM »
Okay.  So w/o cold water running over the condenser, what was the result?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

  • Frequent Member
  • **
  • Posts: 498
Re: 90 burb ac issue
« Reply #10 on: July 29, 2019, 05:06:44 PM »
Same results. Burned up compressor with pressures right on spec.

Sent from my SM-G955U using Tapatalk

'90 Suburban TBI 350

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #11 on: July 29, 2019, 05:40:37 PM »
Cooling the condenser with cold water should drop the high side pressure dramatically to perhaps 150 PSI and the low side pressure moderately to <28 PSI - low enough to cycle the compressor clutch regularly and fairly often.  So, with no intention of disrespect, I don't buy it.  There is more to the story.  How many measured pounds of R134a were added to the system (not as a percentage of the R12 specification, but actual pounds)?  Was the refrigerant an R134a blend or pure?  Are you absolutely certain there is no obstruction in the high-side plumbing?  Is the serpentine condenser that was used physically similar in dimensions to the original?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6438
Re: 90 burb ac issue
« Reply #12 on: July 30, 2019, 06:39:13 PM »
Pondering this further, did the compressor actually "burn up" or did it just expel refrigerant through the pressure relief? 

For a compressor to actually burn up would require lubricant starvation.  Some possibilities for this are a restriction that minimizes or prevents oil circulation, contaminated oil that alters lubricity, insufficient oil charge, or mismounting of the compressor that improperly orients the compressor crankcase. 

You've expressed that system pressures are normal for the ambient temperature and humidity.  Since a restriction would cause abnormal pressure relationships, that can reasonably be ruled out. 

Oil contamination could be caused by mixing of incompatible oils or by inadvertently introducing solvent that dilutes the oil.  You flushed out the complete system and charged with PAG oil, so incompatible oils likely can be eliminated as a variable.  However, when the system was flushed, were the compressor and accumulator excluded from the process?   Neither should be flushed since both will trap solvent and debris, ushering catastrophe.  If they weren’t effectively disconnected and isolated from the system before flushing the lines and other components, they should be replaced.

Since you followed the compressor manufacturer’s recommendation for oil charge, although slightly low in my opinion for a system with rear A/C, that also can be ruled out.

Now, if by ‘compressor burning up’ you actually meant that the pressure release (thermal fuse) opened and dumped refrigerant, then excessive head pressure and associated overheating may have resulted from insufficient heat rejection via the condenser.  Causes for this can be insufficient airflow through the core (a remarkably common scenario) or an undersized/underrated core for the application.

Other possible variables were mentioned previously.  In summary, I suspect that inadequate heat rejection by the condenser is the primary culprit, either due to inadequate airflow through the core or an inadequate core.  I hope this sheds more light on the topic and helps you advance toward resolution.

Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2526
  • Old Goof
Re: 90 burb ac issue
« Reply #13 on: July 31, 2019, 01:23:59 PM »
Bizarre so all I can add is what happens in my industry: bad run of parts.

On my end, the manufacturer said our wiring was wrong causing modules to cook.

Had to show them video of modules burning up when unpacked and powered up.

Try another make of compressor? All I got...
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction