2000 Buick Regal GS heater stops at highway speeds

[DoubleEagle]

First post, did a search but didn't find anything similar.

I have a 2000 Buick Regal GS. Has a dual automatic climate control. The heater works fine when driving around town. However when I go out on the highway it stops working after about 20 or 30 minutes of highway driving. The fan stops blowing and no heat comes out. After slowing down to city speeds, the heater starts working again. Strange.

It is a bit of a problem since the outdoor temps have been very low this winter. I took in to the dealer and they have no idea what is wrong. Any ideas to that might help?

[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.

[DoubleEagle]

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.

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.

[regalfriend]

Odd problem Maybe hook up a volt meter to the fuseblock for the blower motor think there are 2 fuses 1 for low speeds and 1 for high or max. this is one of those gremlins thats a PITA My father had an 84 Electra. Wipers didnt work when it rained Dealer replaced everything and it still happened