Quote:
Originally Posted by BNaylor
Welcome to AF.
Interesting problem. Is the engine operating temperature normal? What are the conditions on the highway? Are you just at cruising speeds. Regardless, check your engine vacuum.
The HVAC system whether automatic and manual climate control uses engine vacuum to operate the various actuators. So check the accessory vacuum line coming off the intake manifold in your case the supercharger and where is routes along the firewall to the area by the battery and main fuse box. From there it goes through the main cable/harness into the cabin. At the cabin into a vacuum booster/cannister.
Engine vacuum is at its highest when the throttle plate is more towards the closed position or at idle.
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Thank you for your reply.
This happens at normal highway conditions on a four lane Interstate highway at a normal cruising speed of about 75 mph. Never had a problem with the engine temps.