HEATER AND AIR CONDITIONING 1A-26
2. The lo ss of system perform ance is not as evident when the com pressor head p re ssu re is below 200 PSI. T herefore, it may be n ecessary to increase the sy s tem head p re ssu re by partially blocking the conden s e r. Disconnect the blower lead w ire and repeat the “ Peform ance Check'’ to determ ine if the evaporator p re ssu re can be obtained. 3. The system will also indicate a low refrig eran t charge by bubbles occurring in the sight glass. System s equipped with a POA Valve req u ire the following additional te s t to determ ine if the de ficiency is the expansion valve. 4. Remove the expansion valve bulb from the evaporator outlet pipe, and the connector on the blower re s is to r. Place the blower on "low." With the engine op erat ing at 2,000 rpm , observe the POA gauge p re ssu re . 5. In sert the expansion valve bulb in a cup of ice. This should re su lt in the POA p re s s u re being reduced to approxim ately 30 P.S.I. If the p re ssu re does not reduce to this level, the POA valve is defective. If the p re ssu re falls considerably below 30 P.S.I., the expansion valve is defective.
CAPILLARY BULB
EXTERNAL EQUALIZER LINE
OUTLET
ENGINE IDLE COMPENSATOR Fig. 33—Expansion Valve
POORLY LOCATED POWER ELEMENT BULB N orm al P re s s u re . Poor Cooling.
Check for Defective Valve The following procedure m ust be followed to determ ine if a malfunction is due to a defective expansion valve. 1. Check to determ ine if the system will m eet the p e r form ance te s t a s outlined previously. If the expan sion valve is defective, the low p re s s u re readings (POA o r evaporator p re ssu re ) will be above specifi cation.
This additional aid to prevent stalling during prolonged hot weather periods is included with all a ir conditioned vehicles. The idle com pensator is a therm ostatically controlled a ir bleed which supplies additional a ir to the idle m ixture. On V-8 engines, with factory installed a ir conditioning system s, the com pensator is located within the ca rb u reto r and is accessible when the engine a ir cleaner is removed. On all other vehicles the compen sato r is threaded into a manifold fitting below the c a r b u retor. All com pensators a re factory set and are nonadjustable. A malfunctioning unit should be replaced. NOTE: If engine idle is e rra tic , hold the idle com pensator valve closed with a pencil or wooden dowel while adjusting the idle m ixture screw (s). Never attem pt to bend the bim etal strip o r attem pt any valve adjustm ent.
COMPONENT PART REPLACEMENT ALL SYSTEMS COMPRESSOR Rem oval (Fig. 34)
1. Purge the re frig e ra n t from the system . 2. Remove connector attaching bolt and connector. Seal connector outlets. 3. D isconnect e le c tric al lead to clutch actuating coil. 4. Loosen b race and pivot bolts and detach belt. 5. Remove the nuts and bolts attaching the co m pressor brack ets to the mounting bracket. 6. Before beginning any co m p resso r disassem bly, drain and m easu re oil in the co m p resso r. Check for evidence of contam ination to determ ine if rem ainder of system re q u ire s servicing. C om pressor s e rv ic ing inform ation is located in the C hassis Overhaul Manual.
Installation
1. If oil previously drained from the co m pressor upon rem oval shows no evidence of contamination, replace a like amount of fresh re frig eratio n oil into the com p re s s o r before reinstallation. If it was n ecessary to service the entire system because of excessive contamination in the oil rem oved, install a full charge of fre sh re frig eratio n oil in the com pressor. 2. Position com pressor on the mounting bracket and install all nuts, bolts and lock w ashers. 3. Install the connector assem bly to the com pressor re a r head, using new "O" rings coated with clean refrig eratio n oil. 4. Connect the e le ctrical lead to the coil and install and adjust com pressor belt. 5. Evacuate, charge and check the system .
10-30 CHEVROLET TRUCK SERVICE MANUAL
