While troubleshooting the cause of hot air blowing from side vents while climbing a long hill with the accelerator pedal to the metal, I noticed that neither defroster vacuum element tubes could hold a vacuum, when the other tube has its normal connection to the switchover valve assembly. The defroster element has two vacuum tubes for a short and long stroke. However, when I disconnected and blocked the other tube, the first tube held vacuum properly both ways.
Is this element working properly?

Please Advice.

NO, any(all) vacuum element(s) must hold vacuum. If you have a leak either repair it or block it off. This car does have a vacuum storage tank under the right front fender to help durning accel.

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