Vent temp differences

[JohnZ71]

Out of curiosity, how much of a temperature difference is expected between the center vent and the driver side vent.

It’s a cooler evening, 76 degrees and I have the heat turned on. The center temp is 107 degrees, while the driver side vent is 82 degrees. The center feels warm, the driver side feels cool.

Seems like a dramatic difference?

I don’t recall ever noticing this much of a difference before, but maybe it has always been like this and therefore normal.

Thoughts?

 

[GoToGuy]

That seems low for the center. What engine temp? The heater core can act as settling pond,. The water is slowed through the core for heat transfer. That also means all those small tubes can collect all the sediment , debris in coolant system. This prevents heat transfer . When flushing system , flush the heat core in and out tubes, watch for mud to blow out.
Is the hot / cool air select sealing , or leaking unheated air to mix.

 

[JohnZ71]

That seems low for the center. What engine temp? The heater core can act as settling pond,. The water is slowed through the core for heat transfer. That also means all those small tubes can collect all the sediment , debris in coolant system. This prevents heat transfer . When flushing system , flush the heat core in and out tubes, watch for mud to blow out.
Is the hot / cool air select sealing , or leaking unheated air to mix.

I didn’t have it on full heat, it was around 1 o’clock. Engine temp was around 182

 

[GoToGuy]

Context matters. That's a mix of hot and cold. I answered as you said. " Heat turned on..."

 

[JohnZ71]

Context matters. That's a mix of hot and cold. I answered as you said. " Heat turned on..."

I’m glad we got that cleared up, now we can be friends again.

I also notice it on humid nights, the air coming out of the front vents is noticeably warmer than the defrost vents, which will fog up the windshield from how much cooler it is.

Could just be the nature of it… I wish I had the courage to try fixing the defrost issue, there is always airflow up there. It’s not too much, but enough that I have to block the vents so my windshield doesn’t fog.

 

[GoToGuy]

Hot moist air, across cooler surface = condensation
Select defrost, fan high gets rid of moisture equalis surface temperatures.
Flapper valves have materials that degrade, so as to not seal, or get sticky and tear off edges, no longer functioning.

 

[Schurkey]

Perhaps a moderator will move this thread out of ENGINES and into OEM + Custom Interiors.

Confirm that this vehicle is your 2000 Tahoe 5.7L.

Let me guess: A/C is non-functional.

Second guess: If the defroster causes the windshield to fog, the heater core is leaking.

The defrost vents are not likely EVER completely shut off. I bet there's always some air-flow through them.

Download the service manual set for your vehicle from the links in the Sticky thread section of the Engine forum. Study the HVAC system including ducting and air-doors/actuators.