Except Fed. 1500 Hf (Cold Engine)
- Ensure engine coolant temperature is below 59°F (15°C). Disconnect vacuum hose No. 2 from vacuum advance diaphragm B. Connect vacuum gauge to hose.
- Start engine and check for vacuum at idle. If there is vacuum, proceed to ALL MODELS (HOT ENGINE) test. There should be vacuum. If there is no vacuum, replace thermovalve B and retest.