Author Topic: A/C problem  (Read 10624 times)

Offline 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
A/C problem
« on: September 01, 2012, 11:22:52 PM »
Well, my 89's ac doesn't work. The clutch doesn't engage on the compressor and the front blower doesn't work on any speed. The rear blower works on low and high. So I started some trial and error to figure it out. Fuses are good. Power to the blower relay when the switches are one. I turned the key on and jumped the large red wire from the relay to the purple blower wire and it turned on. Then I jumped the low pressure switch on the drier to see if the clutch would engage and it wont. I pulled the metal case off of the relay and noticed that the coil wasnt energizing. So when I lifter up the arm that the coil pulls, the blower kicked on, and when I touched power to one of the other wires the clutch kicked on. So I figured the relay was bad. So I pulled the working relay out of my 79 and the coil still doesn't energize on the 89. Any Ideas? it is pretty dang hot out and its killing me.
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5726
Re: A/C problem
« Reply #1 on: September 02, 2012, 12:20:43 AM »
Check the A/C selector and blower switches and their connectors - they have a tendency to Chernobyl.  Jumping the low pressure switch won't engage the clutch if there's no power to the switch.
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 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
Re: A/C problem
« Reply #2 on: September 02, 2012, 12:37:14 AM »
Which wire energizes the coil?
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5726
Re: A/C problem
« Reply #3 on: September 02, 2012, 01:57:12 PM »
Twelve-volt power runs from the dash selector switch to the A/C low pressure switch on the light green wire, then on to the A/C compressor clutch coil via the dark green wire.

As a quick test of the A/C clutch coil and engine compartment harness, unplug the 2-wire connector from the A/C low pressure switch and momentarily jump 12-v battery to the dark green wire in the connector - the clutch coil should energize.
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 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
Re: A/C problem
« Reply #4 on: September 02, 2012, 10:06:02 PM »
I know how to test the the A/C clutch for functionality, but I need to know which wires energize the coil inside of the relay so I can trace them back to the switch. There is like an orange, purple, black, red, and something else going to the relay. Which one energizes the coil in the relay?
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5726
Re: A/C problem
« Reply #5 on: September 02, 2012, 11:15:58 PM »
...I need to know which wires energize the coil inside of the relay so I can trace them back to the switch. There is like an orange, purple, black, red, and something else going to the relay. Which one energizes the coil in the relay?

The relay coil is energized on high blower by the orange wire.  Black is relay coil ground.  Dark blue is from the resistor.
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 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
Re: A/C problem
« Reply #6 on: September 04, 2012, 10:49:43 PM »
Man, what a pain. I'm going to try and run a 12+ to the orange wire and see if the relay energizes, Then I'll know if its a problem with the selector switches. I may even just run a toggle switch to it.
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Offline 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
Re: A/C problem
« Reply #7 on: September 14, 2012, 09:36:49 AM »
Okay, so I ran a wire from the positive battery terminal with a 20amp fusible link and touched it to the orange wire and everything turned on. So, from deductive reasoning, the switch is not sending power to the relay. So, I started the truck up, put A/C max and blower max and turned on the rear air max. The compressor cycles every 3 or so seconds, it doesn't stay on for very long. But, I noticed the air coming from the front vents was warm and the air coming from the rear vents was ICE cold. I'm considering wiring a toggle switch from the dash to the relay in place of the orange wire. Any ideas why the rear air is cold and the front is warm? I think it is still R12, but there is a sticker on the core support with the name Tracer, which is an A/C dye company so I'm wondering if it was converted to R134a. The sticker was faded so I'm not sure and the schrader ports are still the factory R12 fittings. Also, Would there be any issues if I ran a toggle switch to the relay, running off of Keyed power?
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5726
Re: A/C problem
« Reply #8 on: September 14, 2012, 10:00:23 AM »
IMO - The A/C is undercharged, the expansion tube is plugged, the blend door may be out of adjustment, and desiccant has pervaded the system.  The Tracer label is there, probably, because dye was added.

You need to check for leaks, flush the system, replace the expansion tube and accumulator, install the conversion fitting kit and upgrade to 134a.

Why go to the trouble of installing a toggle?  Just replace the A/C selector and blower switches.  My 1.25.
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 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
Re: A/C problem
« Reply #9 on: September 14, 2012, 10:24:36 AM »
BLEND DOOR! You, sir are a genius. I jst remembered that when I was replacing my ecm I noticed the cable on top of the heater box was disconnected. So there is that issue. I can't find new replacements for the  A/C selector or blower switch. I've looked. So only option for that would be junk yard. But, the A/C cycling so often is from low refrigerant?
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5726
Re: A/C problem
« Reply #10 on: September 14, 2012, 10:55:10 AM »
When ambient temp is between ~70 and 90 F, at idle, a properly charged A/C should run almost continuously, w/o cycling.  I will try to find a source for the switches and connectors by tomorrow.
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 1979C20

  • Senior Member
  • ****
  • Posts: 1659
  • Kyle Taulton.
Re: A/C problem
« Reply #11 on: September 14, 2012, 11:02:49 AM »
Its about 90 out and idling, but cycling 3-5 second intervals. How can I see if its r12 or r134a?
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5726
Re: A/C problem
« Reply #12 on: September 14, 2012, 02:09:05 PM »
Parts sourced from AutoZone and A/C Delco...

Blower Switch:
http://www.autozone.com/autozone/parts/Duralast-Blower-Control-Switch/1989-Chevrolet-R1500-1-2ton-Sub-2WD/_/N-ih5r9Z91t6u?itemIdentifier=184481_0_4222_5281

A/C Delco #15-71352

Blower Switch Connector:
http://www.autozone.com/autozone/parts/Duralast-Pigtail-Connector/_/N-9cl7g?itemIdentifier=349718&_requestid=3223983

A/C Delco #PT1936

Blower Switch Knob:
A/C Delco #15-72008

A/C Selector Switch:
http://www.autozone.com/autozone/parts/Everco-A-C-Selector-Mode-Switch/1989-Chevrolet-R1500-1-2ton-Sub-2WD/_/N-ih5r9Z91tp2?itemIdentifier=903054_0_6210_

A/C Delco #15-7004

A/C Selector Switch Connector:
A/C Delco #PT2344

--------------------------------

I know of no practical way to determine precisely what was used to charge your A/C system.  Best approach is to check for leaks, then start over with new accumulator, flush, correct oil, conversion kit, etc and 134a, per my previous post.
« Last Edit: September 14, 2012, 05:20:18 PM by bd »
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 Edahall

  • Frequent Member
  • **
  • Posts: 311
Re: A/C problem
« Reply #13 on: September 14, 2012, 05:04:40 PM »
Its about 90 out and idling, but cycling 3-5 second intervals. How can I see if its r12 or r134a?

Sounds like very low refrigerant.

Check to see if the fittings are for R12 or R134a.

1990 ton 4x4 Chevy Suburban
-Cummins Diesel - 12 valve - factory rebuilt
-6 speed bullet proof manual transmission - NV5600
-Gear Vendors Overdrive
-Upgraded Holset HX-35 turbo
-NP205 iron transfer case
-3.73 gears
-2" Lift

Offline 454Man

  • Senior Member
  • ****
  • Posts: 1027
  • Why Race?
Re: A/C problem
« Reply #14 on: September 14, 2012, 07:22:46 PM »
X2 low on refrigerant. There is a way to tell what kind of freon is in the system, but you need a gauge set and a PT chart(pressure temperature) and a way to take the temp of the line closest to the port that the gauge hose is connected.  You read the pressure on the gauges and the temp on the thermometer. These readings should correspond to what's on the pt chart. look in the r12 and 134a columns. This should be done first thing in the morning before the vehicle is started.