GMC 1986 P-Truck Service Manual page 73

1B-10 AIR CONDITIONING
INSUFFICIENT COOLING-A/C SYSTEMS WITH CYCLING CLUTCH-EXPANSION TUBE (PRESSURE SENSING)
Move Temp. Lever Rapidly Back And Forth From Hot to Cold. Listen For Door Hitting At Each End
-----------------------
This System Does Not Have A Sight Glass Linder No Circumstances Should A Sight Glass Be Installed |
Restriction In High Side Of System. Visually Check For Frost
Spot To Locate Restriction. Repair As Necessary.
| Evacuate & Charge |
System
(O.K.)
( Runs Continuously Within Limits |
Disconnect Blower Wire And Check For
Cycling Off At 138-193 kPa (20-28 PSI)
Pressure Falls
Below 138 kPa (20 PSI)
________ E_____ ,
Defective Pressure Switch I
----------------------------------------------
Replace *Do Not Discharge
System. There Is A Schrader
Valve In The Fitting__________
,____I ____ t
| System (O.K.) |
Ambient Temp.
A/C
Outlet
Temp
Outlet Temperature Within Limits t
3
System (O.K.
| " Discharge System And Check For Missing Expansion Tube |
Install Expansion Tube
| Evacuate & Charge j
I System (O.K.) |
Hitting
T
1 Set Temp Lever Full Cold
2. Set Selector Lever Norm A/C
3 Set Blower Switch On High
---------------------------------------
| Feel For Air Flow At Heater And A/C Outlets
Air Flow From A/C
| Check Visually For Compressor Clutch Operation I
I Engaged Or Cyclingl........... ...
1 i
| Feel Liquid Line Before Expansion Tube |
I Cold l -
| Inlet Pipe And Outlet Pipe Same Temperature Or Outlet Colder Than ln le t|— -
{ Install Gage Set And Check Compressor Cycling Press''|
| On At 2 826-3 516 kPa (41-51 PSI)
Cycles Within Limits
Cycles Off At 138-193
kPa (20-28 PSI) Or Does
Not Pull Down To Press
1
I Install Thermomete|r In A/C Outlet And Check Performance 1
1. Set Temp. Lever To Full Cold
2. Set Selector Lever To Max A/C
3. Set Blower Switch On Hi
21 °C (70°F)
2 7 °C (80°F)
5-8°C
5-8 °C
Pick-Up
(41 -47 °F)
(41 -47°F)
6-9°C 6-9 °C
Suburban
(42-48°F) (42-48 °F)
| In Place |
| Check Compressor Inlet Screen
1 Repair Or Replace S creen l
| Evacuate & Charge |
| Systern (O .K ) |
Figure 11—Pressure Cycling CCOT System Diagnosis
Not
.... 1
4 Open Doors And Hood
5. W arm Engine
6 Run Engine At Idle
Outlets Only
I---------------------------------------------------------
.... -............... — z
------------------------ 1 W arm I
------ LJT J------------
Feel Evaporator Inlet And Outlet Pipes K
Off At 138-193 kPa (20-28 PSI) |
f - - ............ .......... .................
Cycles High Or Low (On Above 51 PSI)
There Is A Schrader Valve in The Fitting
4. Close Doors and Windows
5. Run Engine At 2000 RPM
6. Use Aux. Fan In Front Of Grill
32°C (90°F) 3 8 °C (100°F)
6-10°C
6 -1 1°C
(42-50°F)
(43-57°F)
10-14°C 12-17°C
(54-62°F)
(50-58 °F)
j Outlet Temperature High As Per Chart |
1 Check Compressor Cycling |
j
I Cycle On And Off Or Remains Off For Long Period Of Time |
\
Discharge System And Check For Plugged Expansion Tube |
f
nr
4 Clean |
j System Over Charged |
| Evacuate & Charge j
\
| System (O.K.)
H Adjust Temp. Door |
Some Or All Air Flow
From Heater Outlet
[ Repair As Per Service Manual
- I
Or Off Below 138 kPa (20 PSI)
Defective Pressure Switch |
Replace. Do Not Discharge System.
System
(O.K.)
4 3 °C (110°F)
6 -1 1°C
(43-51 °F)
14-19°C
(57-67 °F)
j j
Replace
I Evacuate & Charge
_ ------t
| SystenT(O.K.) j
F-00162