Hot Engine

Ensure engine is at normal operating temperature. On Civic 1500 models, disconnect vacuum hose from the power valve at the carburetor and plug the hose. See Fig 1 and Figure .
On 1500 models, disconnect vacuum hose from the power steering, remove cover from control box No. 2. On all models, start engine and check that frequency valves A and B are operating while running engine at 2500 RPM.
NOTE: Civic 1500 models equipped with auto. trans. and power steering, frequency solenoid valves are located outside of control box No. 2. Hose No. 6 leads to valve A and hose No. 21 leads to valve B.

Fig 1: View of Civic 1500 Power Valve Vacuum Hose
Frequency valves should emit a clicking sound. It may be easier to place hand on each individual valve to feel movement. If either solenoid A or B is inoperable, replace valve and retest. If both solenoid valves operate properly, proceed to step 6).

Fig 2: Civic 1500 Control Boxes Nos. 1 & 2
If either solenoid A or B are inoperable, check for voltage at terminal lead wires while engine is running at 2500 RPM. If voltmeter fluctuates between 12 volts and 0 volts, replace solenoid valves and retest.
If voltmeter indicates 0 volts, proceed to TROUBLE SHOOTING. If voltmeter indicates 12 volts and engine operating condition is abnormal, or the engine stops, proceed to TROUBLE SHOOTING.
Reconnect vacuum hoses. Then, with A/C, radiator fan, heater blower motor, rear window defogger and headlights off, ensure that frequency solenoid valves are inoperable while at engine is at idle speed.
If solenoid valves are inoperable, the system is okay and testing is complete. If solenoid valves do operate, proceed to TROUBLE SHOOTING.