Bonneville V6-231 3.8L VIN 3 SFI (1988)
1.
Remove radio and inspect vacuum harness connectors located just below and slightly to the left of the rear of the radio (see Fig. 1) The light green
vacuum hose makes a 120 degree turn and could be kinked. Correct as necessary. Rerun temperature lever test.
2.
If the vacuum hose routing is okay, or the condition still exists, remove the glove box and inspect the routing of the light green vacuum hose from
the vacuum harness connector to the Max Heat Door (Heater Slave Door) for pinching. Rerun temperature lever test.
3.
If the condition still exists apply 10" Hg. Vacuum to Max Heat Vacuum valve (Heater Slave Valve). Rerun temperature lever test. If the conditions
still exist, the situation is internal in the heater either a door is binding or vacuum motor defective.