Control Assembly: Testing and Inspection

Adjusting Test Bleed Valve:

Start vacuum pump Tool C-4081 or C-4289 and connect to the vacuum test set Tool C-3707. Adjust bleed valve on test set to obtain vacuum of exactly -27kPag (8 inches of mercury) with a finger blocking the prod on end of test hose.

It is essential that the bleed valve be adjusted so the vacuum gauge pointer will return to exactly -27kPag (8 inches) when the prod is covered by a finger. Otherwise a false reading will be obtained when the control circuit is tested.

CAUTION: Alternately release and reblock the hose prod several times. Make sure the bleed valve is adjusted so the vacuum gauge pointer returns to exactly -27kPag (8 inches of vacuum) when the prod is covered with a finger.

Disconnect engine vacuum source hose at engine intake manifold and insert vacuum tester hose prod into source hose leading to control switch. Place vacuum gauge on the cowl so it can be observed from the driver's position as push buttons are operated.

Start the test by pushing the HEAT button. Vacuum tester gauge needle will drop until the actuator has operated, and should then return to -24.5 to -27kPag (7-1/4 to 8 inches) depending on vacuum leakage. Continue to push buttons; OFF, MAX A/C, A/C, VENT, DEFROST, and HEAT allowing time for actuators to operate after each button is pushed, for the vacuum to stabilize. Note the vacuum drop below -27kPag (8 inches) after each operation. The maximum allowable vacuum drop below -27kPag (8 inches) after each operation is -2.5kPag (3/4 inch).

Push Button Vacuum Test:

If the vacuum drop is more than -2.5kpag (3/4 inch), first recheck the tester for reading exactly -27kPag (8 inches). If correct, inspect the fit of the 7-hole hose connector plug on the control switch. This plug must be positioned all the way on the 7 ports on the control switch.

CAUTION: Do not use lubricant on the switch ports or in the holes in the plug, as lubricant will ruin the vacuum valve in the switch. If it is impossible to properly position the connector plug all the way on the switch ports, put a drop or two of clean water in the holes of the connector plug. This will allow the plug to slide completely on the switch ports.

Vacuum Tube Assembly Test:

If vacuum drop is now within limits, proceed with the over-all performance test. If vacuum drop is still in excess of -2.5kPag (3/4 inch), remove 7 port connector from switch and seal port no. 6 with finger to check source hose. Then remove prod from source line and insert it alternately into each connector hole except No. 6.

Note amount of vacuum drop below -27kPag (8 inches) after each actuator has operated. If vacuum test gauge comes back to -27kPag (8 inches) at each of the 7 holes, the hoses and actuators are not leaking. The control switch is faulty and must be replaced. If excessive vacuum drop shows up at one or more holes in connector block, isolate faulty hose or actuator.

Vacuum Actuator Test:

Inspect hose connections to the actuator involved. Then test whether actuator or hose is at fault; use the test hose on the actuator involved.

A leak in a hose may be detected with leak tester by running the fingers along the hose and watching vacuum gauge reading. The tube can be repaired by cutting out the "leak" and inserting the tube "ends" into a 3mm (1/8 inch) inside diameter rubber tube. Wet the tube with water to aid insertion.

A vacuum drop in excess of -2.5 kPag (3/4 inch) below the -27kPag (8 inches) needed in this test would not interfere with the engine operation, other than perhaps to cause a rough idle. It could, however, interfere with the proper operation of the air-conditioning and heating controls at high speeds and during acceleration.